feat: add ThumbHash support alongside BlurHash across events, uploads, and UI

Adds a parallel ThumbHash placeholder everywhere BlurHash is already used.
Remote events now carry both hashes; renderers prefer thumbhash when
available and fall back to blurhash. The MIP-04 `thumbhash` imeta field
that was previously reserved-but-unused is now wired end-to-end.

- New ThumbHash encoder/decoder in commons/commonMain (no new Gradle dep)
- New ThumbhashTag and thumbhash accessors/builders across NIP-17, 68,
  71, 94, 95, 99, the experimental profile gallery, and MIP-04
- RichTextParser + MediaContentModels carry a thumbhash field alongside
  blurhash so every downstream composable can pick its preferred placeholder
- New ThumbHashFetcher (Android + Desktop) registered with Coil, plus a
  small placeholderModel(thumbhash, blurhash) helper centralising the
  "prefer thumbhash, fall back to blurhash" rule
- Rename BlurhashMetadataCalculator -> PreviewMetadataCalculator; the
  calculator decodes the bitmap / video thumbnail once and runs both
  encoders on the same pixels to keep upload cost flat
- DesktopMediaMetadata, MediaUploadResult, and FileHeader now surface
  both hashes through the NIP-96, Blossom, NIP-95, MIP-04, NIP-17 DM,
  Classifieds, picture, video, and long-form upload paths
- Round-trip unit test for the ThumbHash port

amethyst/src/main/java/com/vitorpamplona/amethyst/model/Account.kt

@@ -228,6 +228,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.magnet
 import com.vitorpamplona.quartz.nip94FileMetadata.mimeType
 import com.vitorpamplona.quartz.nip94FileMetadata.originalHash
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.DimensionTag
+import com.vitorpamplona.quartz.nip94FileMetadata.thumbhash
 import com.vitorpamplona.quartz.nip98HttpAuth.HTTPAuthorizationEvent
 import com.vitorpamplona.quartz.nipA0VoiceMessages.BaseVoiceEvent
 import com.vitorpamplona.quartz.nipA0VoiceMessages.VoiceEvent
@@ -249,6 +250,8 @@ import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 import java.math.BigDecimal
 import kotlin.coroutines.cancellation.CancellationException
+import com.vitorpamplona.quartz.experimental.nip95.header.thumbhash as nip95thumbhash
+import com.vitorpamplona.quartz.experimental.profileGallery.thumbhash as galleryThumbhash
 
 @OptIn(DelicateCoroutinesApi::class)
 @Stable
@@ -1135,6 +1138,7 @@ class Account(
                 headerInfo.mimeType?.let { mimeType(it) }
                 headerInfo.dim?.let { dimension(it) }
                 headerInfo.blurHash?.let { blurhash(it.blurhash) }
+                headerInfo.thumbHash?.let { nip95thumbhash(it.thumbhash) }
 
                 contentWarningReason?.let { contentWarning(contentWarningReason) }
             }
@@ -1219,16 +1223,17 @@ class Account(
         val iMetas =
             urlHeaderInfo.map {
                 PictureMeta(
-                    it.key,
+                    url = it.key,
-                    it.value.mimeType,
+                    mimeType = it.value.mimeType,
-                    it.value.blurHash?.blurhash,
+                    blurhash = it.value.blurHash?.blurhash,
-                    it.value.dim,
+                    dimension = it.value.dim,
-                    caption,
+                    alt = caption,
-                    it.value.hash,
+                    hash = it.value.hash,
-                    it.value.size,
+                    size = it.value.size,
-                    null,
+                    service = null,
-                    emptyList(),
+                    fallback = emptyList(),
-                    emptyList(),
+                    annotations = emptyList(),
+                    thumbhash = it.value.thumbHash?.thumbhash,
                 )
             }
 
@@ -1271,13 +1276,14 @@ class Account(
                         quotes(findNostrUris(it))
                     }
                     pictureIMeta(
-                        url,
+                        url = url,
-                        headerInfo.mimeType,
+                        mimeType = headerInfo.mimeType,
-                        headerInfo.blurHash?.blurhash,
+                        blurhash = headerInfo.blurHash?.blurhash,
-                        headerInfo.dim,
+                        dimension = headerInfo.dim,
-                        headerInfo.hash,
+                        hash = headerInfo.hash,
-                        headerInfo.size,
+                        size = headerInfo.size,
-                        alt,
+                        alt = alt,
+                        thumbhash = headerInfo.thumbHash?.thumbhash,
                     )
                     // add zap splits
                     // add zap raiser
@@ -1295,6 +1301,7 @@ class Account(
                         dimension = headerInfo.dim,
                         blurhash = headerInfo.blurHash?.blurhash,
                         alt = alt,
+                        thumbhash = headerInfo.thumbHash?.thumbhash,
                     )
 
                 if (headerInfo.dim.height > headerInfo.dim.width) {
@@ -1314,6 +1321,7 @@ class Account(
                     headerInfo.mimeType?.let { mimeType(it) }
                     headerInfo.dim?.let { dimension(it) }
                     headerInfo.blurHash?.let { blurhash(it.blurhash) }
+                    headerInfo.thumbHash?.let { thumbhash(it.thumbhash) }
 
                     originalHash?.let { originalHash(it) }
                     magnetUri?.let { magnet(it) }
@@ -2164,6 +2172,7 @@ class Account(
         dim: DimensionTag?,
         hash: String?,
         mimeType: String?,
+        thumbhash: String? = null,
     ) {
         val template =
             ProfileGalleryEntryEvent.build(url) {
@@ -2172,6 +2181,7 @@ class Account(
                 mimeType?.let { mimeType(it) }
                 dim?.let { dimension(it) }
                 blurhash?.let { blurhash(it) }
+                thumbhash?.let { galleryThumbhash(it) }
             }
 
         val event = signer.sign(template)

amethyst/src/main/java/com/vitorpamplona/amethyst/service/images/ImageLoaderSetup.kt

@@ -83,10 +83,12 @@ class ImageLoaderSetup {
                         add(VideoFrameDecoder.Factory())
                         add(Base64Fetcher.Factory)
                         add(BlurHashFetcher.Factory)
+                        add(ThumbHashFetcher.Factory)
                         add(BlossomFetcher.Factory(blossomServerResolver, callFactory))
                         add(ProfilePictureFetcher.Factory(thumbnailCache, callFactory, backgroundScope))
                         add(Base64Fetcher.BKeyer)
                         add(BlurHashFetcher.BKeyer)
+                        add(ThumbHashFetcher.TKeyer)
                         add(ProfilePictureFetcher.BKeyer)
                         add(OkHttpFactory(callFactory))
                     }.build(),

amethyst/src/main/java/com/vitorpamplona/amethyst/service/images/ThumbHashFetcher.kt

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.service.images
+
+import androidx.compose.runtime.Stable
+import coil3.ImageLoader
+import coil3.asImage
+import coil3.decode.DataSource
+import coil3.fetch.FetchResult
+import coil3.fetch.Fetcher
+import coil3.fetch.ImageFetchResult
+import coil3.key.Keyer
+import coil3.request.Options
+import com.vitorpamplona.amethyst.commons.blurhash.toAndroidBitmap
+import com.vitorpamplona.amethyst.commons.thumbhash.ThumbHashDecoder
+
+data class ThumbhashWrapper(
+    val thumbhash: String,
+)
+
+@Stable
+class ThumbHashFetcher(
+    private val options: Options,
+    private val data: ThumbhashWrapper,
+) : Fetcher {
+    override suspend fun fetch(): FetchResult? {
+        val hash = data.thumbhash
+        val platformImage = ThumbHashDecoder.decodeKeepAspectRatio(hash, 25) ?: return null
+        return ImageFetchResult(
+            image = platformImage.toAndroidBitmap().asImage(true),
+            isSampled = false,
+            dataSource = DataSource.MEMORY,
+        )
+    }
+
+    object Factory : Fetcher.Factory<ThumbhashWrapper> {
+        override fun create(
+            data: ThumbhashWrapper,
+            options: Options,
+            imageLoader: ImageLoader,
+        ): Fetcher = ThumbHashFetcher(options, data)
+    }
+
+    object TKeyer : Keyer<ThumbhashWrapper> {
+        override fun key(
+            data: ThumbhashWrapper,
+            options: Options,
+        ): String = data.thumbhash
+    }
+}
+
+/**
+ * Pick the best Coil model for a media placeholder.
+ *
+ * Prefers [ThumbhashWrapper] when a thumbhash is available (better quality, preserves aspect ratio
+ * and alpha) and falls back to [BlurhashWrapper] when only a blurhash is present. Returns null
+ * when neither is available, so callers can skip the placeholder request entirely.
+ */
+fun placeholderModel(
+    thumbhash: String?,
+    blurhash: String?,
+): Any? =
+    when {
+        !thumbhash.isNullOrEmpty() -> ThumbhashWrapper(thumbhash)
+        !blurhash.isNullOrEmpty() -> BlurhashWrapper(blurhash)
+        else -> null
+    }

amethyst/src/main/java/com/vitorpamplona/amethyst/service/playback/composable/VideoView.kt

@@ -68,6 +68,7 @@ fun VideoView(
     onDialog: (() -> Unit)? = null,
     accountViewModel: AccountViewModel,
     alwaysShowVideo: Boolean = false,
+    thumbhash: String? = null,
 ) {
     val borderModifier =
         if (roundedCorner) {
@@ -78,7 +79,7 @@ fun VideoView(
             Modifier
         }
 
-    VideoView(videoUri, mimeType, title, thumb, borderModifier, contentScale, waveform, artworkUri, authorName, dimensions, blurhash, nostrUriCallback, onDialog, alwaysShowVideo, accountViewModel = accountViewModel)
+    VideoView(videoUri, mimeType, title, thumb, borderModifier, contentScale, waveform, artworkUri, authorName, dimensions, blurhash, nostrUriCallback, onDialog, alwaysShowVideo, accountViewModel = accountViewModel, thumbhash = thumbhash)
 }
 
 @Composable
@@ -99,6 +100,7 @@ fun VideoView(
     alwaysShowVideo: Boolean = false,
     showControls: Boolean = true,
     accountViewModel: AccountViewModel,
+    thumbhash: String? = null,
 ) {
     val automaticallyStartPlayback =
         remember {
@@ -107,7 +109,7 @@ fun VideoView(
             )
         }
 
-    if (blurhash == null) {
+    if (blurhash == null && thumbhash == null) {
         val ratio = dimensions?.aspectRatio() ?: MediaAspectRatioCache.get(videoUri)
 
         val modifier =
@@ -154,12 +156,13 @@ fun VideoView(
             }
 
         Box(modifier, contentAlignment = Alignment.Center) {
-            // Always displays Blurharh to avoid size flickering
+            // Always displays a placeholder (thumbhash preferred, blurhash fallback) to avoid size flickering
             DisplayBlurHash(
                 blurhash,
                 null,
                 contentScale,
                 if (ratio != null) borderModifier.aspectRatio(ratio) else borderModifier,
+                thumbhash = thumbhash,
             )
 
             if (!automaticallyStartPlayback.value) {

amethyst/src/main/java/com/vitorpamplona/amethyst/service/uploads/FileHeader.kt

@@ -22,6 +22,7 @@ package com.vitorpamplona.amethyst.service.uploads
 
 import android.media.MediaDataSource
 import com.vitorpamplona.amethyst.service.images.BlurhashWrapper
+import com.vitorpamplona.amethyst.service.images.ThumbhashWrapper
 import com.vitorpamplona.quartz.nip01Core.core.toHexKey
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.DimensionTag
 import com.vitorpamplona.quartz.utils.Log
@@ -36,6 +37,7 @@ class FileHeader(
     val size: Int,
     val dim: DimensionTag?,
     val blurHash: BlurhashWrapper?,
+    val thumbHash: ThumbhashWrapper? = null,
 ) {
     class UnableToDownload(
         val fileUrl: String,
@@ -71,9 +73,9 @@ class FileHeader(
                 val hash = sha256(data).toHexKey()
                 val size = data.size
 
-                val (blurHash, dim) = BlurhashMetadataCalculator.computeFromBytes(data, mimeType, dimPrecomputed)
+                val preview = PreviewMetadataCalculator.computeFromBytes(data, mimeType, dimPrecomputed)
 
-                Result.success(FileHeader(mimeType, hash, size, dim, blurHash))
+                Result.success(FileHeader(mimeType, hash, size, preview.dim, preview.blurhash, preview.thumbhash))
             } catch (e: Exception) {
                 if (e is CancellationException) throw e
                 Log.e("ImageDownload") { "Couldn't convert image in to File Header: ${e.message}" }

amethyst/src/main/java/com/vitorpamplona/amethyst/service/uploads/MediaUploadResult.kt

@@ -21,6 +21,7 @@
 package com.vitorpamplona.amethyst.service.uploads
 
 import com.vitorpamplona.amethyst.service.images.BlurhashWrapper
+import com.vitorpamplona.amethyst.service.images.ThumbhashWrapper
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.DimensionTag
 
@@ -45,12 +46,15 @@ data class MediaUploadResult(
     val ipfs: String? = null,
     // blurhash value for previews
     val blurHash: BlurhashWrapper? = null,
+    // thumbhash value for previews (preferred over blurhash in the UI)
+    val thumbHash: ThumbhashWrapper? = null,
 ) {
-    fun mergeLocalMetadata(localMetadata: Pair<BlurhashWrapper?, DimensionTag?>?): MediaUploadResult =
+    fun mergeLocalMetadata(localMetadata: PreviewHashes?): MediaUploadResult =
-        localMetadata?.let { (blur, dim) ->
+        localMetadata?.let { hashes ->
             copy(
-                dimension = dim ?: dimension,
+                dimension = hashes.dim ?: dimension,
-                blurHash = blur ?: blurHash,
+                blurHash = hashes.blurhash ?: blurHash,
+                thumbHash = hashes.thumbhash ?: thumbHash,
             )
         } ?: this
 }

amethyst/src/main/java/com/vitorpamplona/amethyst/service/uploads/PreviewMetadataCalculator.kt

@@ -26,11 +26,28 @@ import android.graphics.BitmapFactory
 import android.media.MediaMetadataRetriever
 import android.net.Uri
 import com.vitorpamplona.amethyst.commons.blurhash.toBlurhash
+import com.vitorpamplona.amethyst.commons.thumbhash.toThumbhash
 import com.vitorpamplona.amethyst.service.images.BlurhashWrapper
+import com.vitorpamplona.amethyst.service.images.ThumbhashWrapper
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.DimensionTag
 import com.vitorpamplona.quartz.utils.Log
 
-object BlurhashMetadataCalculator {
+/**
+ * Result of precomputing placeholder metadata during an upload. The bitmap or video thumbnail is
+ * decoded exactly once and both hashes are computed from the same pixels to keep the hot upload
+ * path cheap.
+ */
+data class PreviewHashes(
+    val blurhash: BlurhashWrapper? = null,
+    val thumbhash: ThumbhashWrapper? = null,
+    val dim: DimensionTag? = null,
+) {
+    companion object {
+        val EMPTY = PreviewHashes()
+    }
+}
+
+object PreviewMetadataCalculator {
     private fun isImage(mimeType: String?) = mimeType?.startsWith("image/", ignoreCase = true) == true
 
     private fun isVideo(mimeType: String?) = mimeType?.startsWith("video/", ignoreCase = true) == true
@@ -42,19 +59,11 @@ object BlurhashMetadataCalculator {
             inPreferredConfig = Bitmap.Config.ARGB_8888
         }
 
-    private fun processImage(
-        bitmap: Bitmap?,
-        dimPrecomputed: DimensionTag?,
-    ): Pair<BlurhashWrapper?, DimensionTag?> {
-        val (blur, dim) = processBitmap(bitmap)
-        return blur to (dim ?: dimPrecomputed)
-    }
-
     fun computeFromBytes(
         data: ByteArray,
         mimeType: String?,
         dimPrecomputed: DimensionTag?,
-    ): Pair<BlurhashWrapper?, DimensionTag?> =
+    ): PreviewHashes =
         when {
             isImage(mimeType) -> {
                 val bitmap = BitmapFactory.decodeByteArray(data, 0, data.size, createBitmapOptions())
@@ -72,7 +81,7 @@ object BlurhashMetadataCalculator {
             }
 
             else -> {
-                null to dimPrecomputed
+                PreviewHashes(dim = dimPrecomputed)
             }
         }
 
@@ -81,7 +90,7 @@ object BlurhashMetadataCalculator {
         uri: Uri,
         mimeType: String?,
         dimPrecomputed: DimensionTag? = null,
-    ): Pair<BlurhashWrapper?, DimensionTag?>? {
+    ): PreviewHashes? {
         if (!shouldAttempt(mimeType)) return null
 
         return try {
@@ -90,7 +99,7 @@ object BlurhashMetadataCalculator {
                     context.contentResolver.openInputStream(uri)?.use { stream ->
                         val bitmap = BitmapFactory.decodeStream(stream, null, createBitmapOptions())
                         processImage(bitmap, dimPrecomputed)
-                    } ?: (null to dimPrecomputed)
+                    } ?: PreviewHashes(dim = dimPrecomputed)
                 }
 
                 isVideo(mimeType) -> {
@@ -108,33 +117,44 @@ object BlurhashMetadataCalculator {
                 }
             }
         } catch (e: Exception) {
-            Log.w("BlurhashMetadataCalc", "Failed to compute metadata from uri", e)
+            Log.w("PreviewMetadataCalc", "Failed to compute metadata from uri", e)
             null
         }
     }
 
-    private fun processBitmap(bitmap: Bitmap?): Pair<BlurhashWrapper?, DimensionTag?> =
+    private fun processImage(
+        bitmap: Bitmap?,
+        dimPrecomputed: DimensionTag?,
+    ): PreviewHashes {
+        val hashes = processBitmap(bitmap)
+        return hashes.copy(dim = hashes.dim ?: dimPrecomputed)
+    }
+
+    private fun processBitmap(bitmap: Bitmap?): PreviewHashes =
         if (bitmap != null) {
             try {
-                val blurhash = BlurhashWrapper(bitmap.toBlurhash())
+                val blurhash = runCatching { BlurhashWrapper(bitmap.toBlurhash()) }.getOrNull()
-                blurhash to DimensionTag(bitmap.width, bitmap.height)
+                val thumbhash = runCatching { ThumbhashWrapper(bitmap.toThumbhash()) }.getOrNull()
+                PreviewHashes(
+                    blurhash = blurhash,
+                    thumbhash = thumbhash,
+                    dim = DimensionTag(bitmap.width, bitmap.height),
+                )
             } finally {
                 bitmap.recycle()
             }
         } else {
-            null to null
+            PreviewHashes.EMPTY
         }
 
     private fun processRetriever(
         retriever: MediaMetadataRetriever,
         dimPrecomputed: DimensionTag?,
-    ): Pair<BlurhashWrapper?, DimensionTag?> {
+    ): PreviewHashes {
         val dim = retriever.prepareDimFromVideo() ?: dimPrecomputed
-        val blurhash = retriever.getThumbnail()?.toBlurhash()?.let { BlurhashWrapper(it) }
+        val thumb = retriever.getThumbnail()
-        return if (dim?.hasSize() == true) {
+        val hashes = processBitmap(thumb)
-            blurhash to dim
+        val finalDim = if (dim?.hasSize() == true) dim else hashes.dim
-        } else {
+        return hashes.copy(dim = finalDim)
-            blurhash to null
-        }
     }
 }

amethyst/src/main/java/com/vitorpamplona/amethyst/service/uploads/blossom/BlossomUploader.kt

@@ -28,8 +28,8 @@ import android.webkit.MimeTypeMap
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.service.HttpStatusMessages
 import com.vitorpamplona.amethyst.service.checkNotInMainThread
-import com.vitorpamplona.amethyst.service.uploads.BlurhashMetadataCalculator
 import com.vitorpamplona.amethyst.service.uploads.MediaUploadResult
+import com.vitorpamplona.amethyst.service.uploads.PreviewMetadataCalculator
 import com.vitorpamplona.amethyst.ui.stringRes
 import com.vitorpamplona.quartz.nip01Core.core.HexKey
 import com.vitorpamplona.quartz.nip01Core.core.JsonMapper
@@ -95,7 +95,7 @@ class BlossomUploader {
                 hashBytes.toHexKey() to totalBytes
             }
 
-        val localMetadata = BlurhashMetadataCalculator.computeFromUri(context, uri, myContentType)
+        val localMetadata = PreviewMetadataCalculator.computeFromUri(context, uri, myContentType)
 
         val imageInputStream = contentResolver.openInputStream(uri)
         checkNotNull(imageInputStream) { "Can't open the image input stream" }

amethyst/src/main/java/com/vitorpamplona/amethyst/service/uploads/nip96/Nip96Uploader.kt

@@ -30,8 +30,8 @@ import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.service.HttpStatusMessages
 import com.vitorpamplona.amethyst.service.checkNotInMainThread
-import com.vitorpamplona.amethyst.service.uploads.BlurhashMetadataCalculator
 import com.vitorpamplona.amethyst.service.uploads.MediaUploadResult
+import com.vitorpamplona.amethyst.service.uploads.PreviewMetadataCalculator
 import com.vitorpamplona.amethyst.ui.stringRes
 import com.vitorpamplona.quartz.nip01Core.core.JsonMapper
 import com.vitorpamplona.quartz.nip36SensitiveContent.ContentWarningTag
@@ -107,7 +107,7 @@ class Nip96Uploader {
         val myContentType = contentType ?: contentResolver.getType(uri)
         val length = size ?: contentResolver.querySize(uri) ?: fileSize(uri) ?: 0
 
-        val localMetadata = BlurhashMetadataCalculator.computeFromUri(context, uri, myContentType)
+        val localMetadata = PreviewMetadataCalculator.computeFromUri(context, uri, myContentType)
         val imageInputStream = contentResolver.openInputStream(uri)
 
         checkNotNull(imageInputStream) { "Can't open the image input stream" }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/actions/EditPostViewModel.kt

@@ -62,6 +62,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.mimeType
 import com.vitorpamplona.quartz.nip94FileMetadata.originalHash
 import com.vitorpamplona.quartz.nip94FileMetadata.sensitiveContent
 import com.vitorpamplona.quartz.nip94FileMetadata.size
+import com.vitorpamplona.quartz.nip94FileMetadata.thumbhash
 import kotlinx.collections.immutable.ImmutableList
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
@@ -233,6 +234,8 @@ open class EditPostViewModel : ViewModel() {
                                             ?.let { dims(it) }
                                         state.result.fileHeader.blurHash
                                             ?.let { blurhash(it.blurhash) }
+                                        state.result.fileHeader.thumbHash
+                                            ?.let { thumbhash(it.thumbhash) }
                                         state.result.magnet?.let { magnet(it) }
                                         state.result.uploadedHash?.let { originalHash(it) }
                                         alt?.let { alt(it) }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/components/SensitivityWarning.kt

@@ -207,14 +207,16 @@ fun ContentWarningNoteWithBigReasonPreview() {
 
 @Composable
 fun BlurhashBackdrop(
-    blurhash: String,
+    blurhash: String?,
     description: String?,
+    thumbhash: String? = null,
 ) {
     DisplayBlurHash(
         blurhash = blurhash,
         description = description,
         contentScale = ContentScale.Crop,
         modifier = Modifier.fillMaxSize(),
+        thumbhash = thumbhash,
     )
 }
 
@@ -222,12 +224,13 @@ fun BlurhashBackdrop(
 fun BlurhashGridBackdrop(media: List<MediaUrlImage>) {
     AutoNonlazyGrid(media.size) { idx ->
         val item = media[idx]
-        if (item.blurhash != null) {
+        if (item.blurhash != null || item.thumbhash != null) {
             DisplayBlurHash(
                 blurhash = item.blurhash,
                 description = item.description,
                 contentScale = ContentScale.Crop,
                 modifier = Modifier.fillMaxSize(),
+                thumbhash = item.thumbhash,
             )
         }
     }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/components/ZoomableContentView.kt

@@ -91,7 +91,6 @@ import com.vitorpamplona.amethyst.commons.richtext.MediaUrlImage
 import com.vitorpamplona.amethyst.commons.richtext.MediaUrlPdf
 import com.vitorpamplona.amethyst.commons.richtext.MediaUrlVideo
 import com.vitorpamplona.amethyst.model.MediaAspectRatioCache
-import com.vitorpamplona.amethyst.service.images.BlurhashWrapper
 import com.vitorpamplona.amethyst.service.playback.composable.VideoView
 import com.vitorpamplona.amethyst.service.uploads.blossom.bud10.openBlossomUriAsIntent
 import com.vitorpamplona.amethyst.ui.actions.CrossfadeIfEnabled
@@ -162,7 +161,7 @@ fun ZoomableContentView(
                 preloadUrls = listOf(content.url),
                 accountViewModel = accountViewModel,
                 modifier = mediaSizingModifier(ratio, contentScale),
-                backdrop = content.blurhash?.let { blurhash -> { BlurhashBackdrop(blurhash, content.description) } },
+                backdrop = (content.thumbhash ?: content.blurhash)?.let { { BlurhashBackdrop(content.blurhash, content.description, content.thumbhash) } },
             ) {
                 TwoSecondController(content) { controllerVisible ->
                     val mainImageModifier =
@@ -184,7 +183,7 @@ fun ZoomableContentView(
                 preloadUrls = emptyList(),
                 accountViewModel = accountViewModel,
                 modifier = mediaSizingModifier(ratio, contentScale),
-                backdrop = content.blurhash?.let { blurhash -> { BlurhashBackdrop(blurhash, content.description) } },
+                backdrop = (content.thumbhash ?: content.blurhash)?.let { { BlurhashBackdrop(content.blurhash, content.description, content.thumbhash) } },
             ) {
                 Box(
                     modifier = Modifier.fillMaxWidth().then(boundsTrackingModifier),
@@ -203,6 +202,7 @@ fun ZoomableContentView(
                         nostrUriCallback = content.uri,
                         onDialog = { dialogOpen = true },
                         accountViewModel = accountViewModel,
+                        thumbhash = content.thumbhash,
                     )
                 }
             }
@@ -330,13 +330,14 @@ fun LocalImageView(
                     when (state) {
                         is AsyncImagePainter.State.Loading,
                         -> {
-                            if (content.blurhash != null) {
+                            if (content.blurhash != null || content.thumbhash != null) {
                                 if (ratio != null) {
                                     DisplayBlurHash(
                                         content.blurhash,
                                         content.description,
                                         contentScale,
                                         loadedImageModifier.aspectRatio(ratio),
+                                        thumbhash = content.thumbhash,
                                     )
                                 } else {
                                     DisplayBlurHash(
@@ -344,6 +345,7 @@ fun LocalImageView(
                                         content.description,
                                         contentScale,
                                         loadedImageModifier,
+                                        thumbhash = content.thumbhash,
                                     )
                                 }
                             } else {
@@ -389,7 +391,7 @@ fun LocalImageView(
                     }
                 }
             } else {
-                if (content.blurhash != null && ratio != null) {
+                if ((content.blurhash != null || content.thumbhash != null) && ratio != null) {
                     DisplayBlurHash(
                         content.blurhash,
                         content.description,
@@ -397,6 +399,7 @@ fun LocalImageView(
                         loadedImageModifier
                             .aspectRatio(ratio)
                             .clickable { showImage.value = true },
+                        thumbhash = content.thumbhash,
                     )
                     IconButton(
                         modifier = Modifier.size(Size75dp),
@@ -460,7 +463,7 @@ fun UrlImageView(
                 when (state) {
                     is AsyncImagePainter.State.Loading,
                     -> {
-                        if (content.blurhash != null) {
+                        if (content.blurhash != null || content.thumbhash != null) {
                             if (ratio != null) {
                                 val modifier =
                                     if (contentScale == ContentScale.Crop) {
@@ -474,6 +477,7 @@ fun UrlImageView(
                                     content.description,
                                     ContentScale.Crop,
                                     modifier,
+                                    thumbhash = content.thumbhash,
                                 )
                             } else {
                                 DisplayBlurHash(
@@ -481,6 +485,7 @@ fun UrlImageView(
                                     content.description,
                                     ContentScale.Crop,
                                     loadedImageModifier,
+                                    thumbhash = content.thumbhash,
                                 )
                             }
                         } else {
@@ -515,7 +520,7 @@ fun UrlImageView(
                 }
             }
         } else {
-            if (content.blurhash != null && ratio != null) {
+            if ((content.blurhash != null || content.thumbhash != null) && ratio != null) {
                 val modifier =
                     if (contentScale == ContentScale.Crop) {
                         loadedImageModifier.clickable { showImage.value = true }
@@ -528,6 +533,7 @@ fun UrlImageView(
                     content.description,
                     contentScale,
                     modifier,
+                    thumbhash = content.thumbhash,
                 )
                 IconButton(
                     modifier = Modifier.size(Size75dp),
@@ -786,11 +792,14 @@ fun DisplayBlurHash(
     description: String?,
     contentScale: ContentScale,
     modifier: Modifier,
+    thumbhash: String? = null,
 ) {
-    if (blurhash == null) return
+    val model =
+        com.vitorpamplona.amethyst.service.images
+            .placeholderModel(thumbhash, blurhash) ?: return
 
     AsyncImage(
-        model = BlurhashWrapper(blurhash),
+        model = model,
         contentDescription = description,
         contentScale = contentScale,
         modifier = modifier,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/nip22Comments/CommentPostViewModel.kt

@@ -109,6 +109,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.mimeType
 import com.vitorpamplona.quartz.nip94FileMetadata.originalHash
 import com.vitorpamplona.quartz.nip94FileMetadata.sensitiveContent
 import com.vitorpamplona.quartz.nip94FileMetadata.size
+import com.vitorpamplona.quartz.nip94FileMetadata.thumbhash
 import com.vitorpamplona.quartz.utils.TimeUtils
 import kotlinx.collections.immutable.ImmutableList
 import kotlinx.coroutines.Dispatchers
@@ -543,6 +544,8 @@ open class CommentPostViewModel :
                                             ?.let { dims(it) }
                                         state.result.fileHeader.blurHash
                                             ?.let { blurhash(it.blurhash) }
+                                        state.result.fileHeader.thumbHash
+                                            ?.let { thumbhash(it.thumbhash) }
                                         state.result.magnet?.let { magnet(it) }
                                         state.result.uploadedHash?.let { originalHash(it) }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/Classifieds.kt

@@ -70,6 +70,7 @@ fun RenderClassifieds(
                 dim = it.dimension,
                 uri = note.toNostrUri(),
                 mimeType = it.mimeType,
+                thumbhash = it.thumbhash,
             )
         }
     val title = noteEvent.title()

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/FileHeader.kt

@@ -49,6 +49,7 @@ fun FileHeaderDisplay(
     val content by
         remember(note) {
             val blurHash = event.blurhash()
+            val thumbHash = event.thumbhash()
             val hash = event.hash()
             val dimensions = event.dimensions()
             val description = event.content.ifEmpty { null } ?: event.alt()
@@ -66,6 +67,7 @@ fun FileHeaderDisplay(
                         dim = dimensions,
                         uri = uri,
                         mimeType = mimeType,
+                        thumbhash = thumbHash,
                     )
                 } else {
                     MediaUrlVideo(
@@ -77,6 +79,7 @@ fun FileHeaderDisplay(
                         uri = uri,
                         authorName = note.author?.toBestDisplayName(),
                         mimeType = mimeType,
+                        thumbhash = thumbHash,
                     )
                 },
             )

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/FileStorage.kt

@@ -76,6 +76,7 @@ private fun ObserverAndRenderNIP95(
             val uri = header.toNostrUri()
             val localDir = note.idHex.let { File(Amethyst.instance.nip95cache, it) }
             val blurHash = eventHeader.blurhash()
+            val thumbHash = eventHeader.thumbhash()
             val dimensions = eventHeader.dimensions()
             val description = eventHeader.alt() ?: eventHeader.content
             val mimeType = eventHeader.mimeType()
@@ -90,6 +91,7 @@ private fun ObserverAndRenderNIP95(
                         blurhash = blurHash,
                         isVerified = true,
                         uri = uri,
+                        thumbhash = thumbHash,
                     )
                 } else {
                     MediaLocalVideo(
@@ -100,6 +102,8 @@ private fun ObserverAndRenderNIP95(
                         isVerified = true,
                         uri = uri,
                         authorName = header.author?.toBestDisplayName(),
+                        blurhash = blurHash,
+                        thumbhash = thumbHash,
                     )
                 }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/PictureDisplay.kt

@@ -85,6 +85,7 @@ fun PictureDisplay(
                             dim = it.dimension,
                             uri = uri,
                             mimeType = it.mimeType,
+                            thumbhash = it.thumbhash,
                         )
                     }.toImmutableList(),
             )
@@ -116,7 +117,7 @@ fun PictureDisplay(
                     preloadUrls = listOf(first.url),
                     accountViewModel = accountViewModel,
                     modifier = mediaSizingModifier(ratio, ContentScale.FillWidth),
-                    backdrop = first.blurhash?.let { blurhash -> { BlurhashBackdrop(blurhash, first.description) } },
+                    backdrop = (first.thumbhash ?: first.blurhash)?.let { { BlurhashBackdrop(first.blurhash, first.description, first.thumbhash) } },
                 ) {
                     ZoomableContentView(
                         content = first,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/Video.kt

@@ -103,6 +103,7 @@ fun VideoDisplay(
                         dim = imeta.dimension,
                         uri = uri,
                         mimeType = imeta.mimeType,
+                        thumbhash = imeta.thumbhash,
                     )
                 } else {
                     MediaUrlVideo(
@@ -115,6 +116,7 @@ fun VideoDisplay(
                         artworkUri = imeta.image.firstOrNull(),
                         mimeType = imeta.mimeType,
                         blurhash = imeta.blurhash,
+                        thumbhash = imeta.thumbhash,
                     )
                 },
             )

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/VideoDisplay.kt

@@ -71,6 +71,7 @@ fun JustVideoDisplay(
                         dim = imeta.dimension,
                         uri = note.toNostrUri(),
                         mimeType = imeta.mimeType,
+                        thumbhash = imeta.thumbhash,
                     )
                 } else {
                     MediaUrlVideo(
@@ -82,6 +83,7 @@ fun JustVideoDisplay(
                         uri = note.toNostrUri(),
                         authorName = note.author?.toBestDisplayName(),
                         mimeType = imeta.mimeType,
+                        thumbhash = imeta.thumbhash,
                     )
                 },
             )
@@ -95,7 +97,7 @@ fun JustVideoDisplay(
         preloadUrls = if (isImage) listOf(imeta.url) else emptyList(),
         accountViewModel = accountViewModel,
         modifier = mediaSizingModifier(ratio, contentScale),
-        backdrop = imeta.blurhash?.let { blurhash -> { BlurhashBackdrop(blurhash, content.description) } },
+        backdrop = (imeta.thumbhash ?: imeta.blurhash)?.let { { BlurhashBackdrop(imeta.blurhash, content.description, imeta.thumbhash) } },
     ) {
         ZoomableContentView(
             content = content,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/feed/types/RenderEncryptedFile.kt

@@ -79,6 +79,7 @@ fun RenderEncryptedFile(
                         encryptionAlgo = algo,
                         encryptionKey = key,
                         encryptionNonce = nonce,
+                        thumbhash = noteEvent.thumbhash(),
                     )
                 } else {
                     EncryptedMediaUrlVideo(
@@ -93,6 +94,7 @@ fun RenderEncryptedFile(
                         encryptionAlgo = algo,
                         encryptionKey = key,
                         encryptionNonce = nonce,
+                        thumbhash = noteEvent.thumbhash(),
                     )
                 },
             )

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/feed/types/RenderMarmotEncryptedMedia.kt

@@ -139,6 +139,7 @@ private fun RenderMip04Content(
                     encryptionAlgo = meta.version,
                     encryptionKey = exporterSecret,
                     encryptionNonce = meta.nonceBytes,
+                    thumbhash = meta.thumbhash,
                 )
             } else {
                 EncryptedMediaUrlVideo(
@@ -153,6 +154,7 @@ private fun RenderMip04Content(
                     encryptionAlgo = meta.version,
                     encryptionKey = exporterSecret,
                     encryptionNonce = meta.nonceBytes,
+                    thumbhash = meta.thumbhash,
                 )
             },
         )

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/marmotGroup/send/MarmotFileSender.kt

@@ -43,6 +43,7 @@ class MarmotFileSender(
                     nonce = upload.nonce,
                     dimensions = upload.dimensions,
                     blurhash = upload.blurhash,
+                    thumbhash = upload.thumbhash,
                 )
 
             accountViewModel.sendMarmotGroupMediaMessage(

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/marmotGroup/send/MarmotFileUploader.kt

@@ -43,6 +43,7 @@ class Mip04UploadResult(
     val dimensions: String?,
     val blurhash: String?,
     val caption: String?,
+    val thumbhash: String? = null,
 )
 
 /**
@@ -102,6 +103,7 @@ class MarmotFileUploader(
                         dimensions = serverResult.fileHeader.dim?.toString(),
                         blurhash = serverResult.fileHeader.blurHash?.blurhash,
                         caption = viewState.caption.ifEmpty { null },
+                        thumbhash = serverResult.fileHeader.thumbHash?.thumbhash,
                     ),
                 )
             } else {

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/IMetaAttachments.kt

@@ -38,6 +38,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.mimeType
 import com.vitorpamplona.quartz.nip94FileMetadata.originalHash
 import com.vitorpamplona.quartz.nip94FileMetadata.sensitiveContent
 import com.vitorpamplona.quartz.nip94FileMetadata.size
+import com.vitorpamplona.quartz.nip94FileMetadata.thumbhash
 import okhttp3.OkHttpClient
 import java.util.Locale
 
@@ -60,6 +61,7 @@ class IMetaAttachments {
                         it.mimeType?.let { mimeType(it) }
                         it.dim?.let { dims(it) }
                         it.blurHash?.let { blurhash(it.blurhash) }
+                        it.thumbHash?.let { thumbhash(it.thumbhash) }
                     }.build()
             }
 
@@ -101,6 +103,7 @@ class IMetaAttachments {
                 result.fileHeader.mimeType?.let { mimeType(it) }
                 result.fileHeader.dim?.let { dims(it) }
                 result.fileHeader.blurHash?.let { blurhash(it.blurhash) }
+                result.fileHeader.thumbHash?.let { thumbhash(it.thumbhash) }
                 result.magnet?.let { magnet(it) }
                 result.uploadedHash?.let { originalHash(it) }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/NewGroupDMScreen.kt

@@ -626,6 +626,9 @@ fun ShowImageUploadGallery(
                         encryptionAlgo = data.cipher.name(),
                         encryptionKey = data.cipher.keyBytes,
                         encryptionNonce = data.cipher.nonce,
+                        thumbhash =
+                            data.result.fileHeader.thumbHash
+                                ?.thumbhash,
                     )
                 } else {
                     EncryptedMediaUrlVideo(
@@ -641,6 +644,9 @@ fun ShowImageUploadGallery(
                         encryptionAlgo = data.cipher.name(),
                         encryptionKey = data.cipher.keyBytes,
                         encryptionNonce = data.cipher.nonce,
+                        thumbhash =
+                            data.result.fileHeader.thumbHash
+                                ?.thumbhash,
                     )
                 }
             } else {
@@ -655,6 +661,9 @@ fun ShowImageUploadGallery(
                         dim = data.result.fileHeader.dim,
                         uri = null,
                         mimeType = data.result.mimeTypeBeforeEncryption,
+                        thumbhash =
+                            data.result.fileHeader.thumbHash
+                                ?.thumbhash,
                     )
                 } else {
                     MediaUrlVideo(
@@ -667,6 +676,9 @@ fun ShowImageUploadGallery(
                         dim = data.result.fileHeader.dim,
                         uri = null,
                         mimeType = data.result.mimeTypeBeforeEncryption,
+                        thumbhash =
+                            data.result.fileHeader.thumbHash
+                                ?.thumbhash,
                     )
                 }
             },

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/privateDM/send/upload/ChatFileSender.kt

@@ -64,6 +64,7 @@ class ChatFileSender(
                 size = result.fileHeader.size,
                 dimension = result.fileHeader.dim,
                 blurhash = result.fileHeader.blurHash?.blurhash,
+                thumbhash = result.fileHeader.thumbHash?.thumbhash,
             ) {
                 if (!caption.isNullOrEmpty()) {
                     alt(caption)

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip23LongForm/LongFormPostViewModel.kt

@@ -105,6 +105,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.mimeType
 import com.vitorpamplona.quartz.nip94FileMetadata.originalHash
 import com.vitorpamplona.quartz.nip94FileMetadata.sensitiveContent
 import com.vitorpamplona.quartz.nip94FileMetadata.size
+import com.vitorpamplona.quartz.nip94FileMetadata.thumbhash
 import com.vitorpamplona.quartz.utils.Log
 import com.vitorpamplona.quartz.utils.RandomInstance
 import com.vitorpamplona.quartz.utils.TimeUtils
@@ -544,6 +545,8 @@ class LongFormPostViewModel :
                                             ?.let { dims(it) }
                                         state.result.fileHeader.blurHash
                                             ?.let { blurhash(it.blurhash) }
+                                        state.result.fileHeader.thumbHash
+                                            ?.let { thumbhash(it.thumbhash) }
                                         state.result.magnet?.let { magnet(it) }
                                         state.result.uploadedHash?.let { originalHash(it) }
                                         alt?.let { alt(it) }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/discover/nip99Classifieds/NewProductViewModel.kt

@@ -429,14 +429,18 @@ open class NewProductViewModel :
                             ) {
                                 productImages = productImages +
                                     ProductImageMeta(
-                                        it.result.url,
+                                        url = it.result.url,
-                                        it.result.fileHeader.mimeType,
+                                        mimeType = it.result.fileHeader.mimeType,
-                                        it.result.fileHeader.blurHash
+                                        blurhash =
-                                            ?.blurhash,
+                                            it.result.fileHeader.blurHash
-                                        it.result.fileHeader.dim,
+                                                ?.blurhash,
-                                        alt,
+                                        dimension = it.result.fileHeader.dim,
-                                        it.result.fileHeader.hash,
+                                        alt = alt,
-                                        it.result.fileHeader.size,
+                                        hash = it.result.fileHeader.hash,
+                                        size = it.result.fileHeader.size,
+                                        thumbhash =
+                                            it.result.fileHeader.thumbHash
+                                                ?.thumbhash,
                                     )
                             } else {
                                 iMetaDescription.add(it.result, alt, contentWarningReason)

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/home/ShortNotePostViewModel.kt

@@ -139,6 +139,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.mimeType
 import com.vitorpamplona.quartz.nip94FileMetadata.originalHash
 import com.vitorpamplona.quartz.nip94FileMetadata.sensitiveContent
 import com.vitorpamplona.quartz.nip94FileMetadata.size
+import com.vitorpamplona.quartz.nip94FileMetadata.thumbhash
 import com.vitorpamplona.quartz.nipA0VoiceMessages.AudioMeta
 import com.vitorpamplona.quartz.nipA0VoiceMessages.BaseVoiceEvent
 import com.vitorpamplona.quartz.nipA0VoiceMessages.VoiceEvent
@@ -1124,6 +1125,8 @@ open class ShortNotePostViewModel :
                                             ?.let { dims(it) }
                                         state.result.fileHeader.blurHash
                                             ?.let { blurhash(it.blurhash) }
+                                        state.result.fileHeader.thumbHash
+                                            ?.let { thumbhash(it.thumbhash) }
                                         state.result.magnet?.let { magnet(it) }
                                         state.result.uploadedHash?.let { originalHash(it) }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/notifications/publicMessages/NewPublicMessageViewModel.kt

@@ -107,6 +107,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.mimeType
 import com.vitorpamplona.quartz.nip94FileMetadata.originalHash
 import com.vitorpamplona.quartz.nip94FileMetadata.sensitiveContent
 import com.vitorpamplona.quartz.nip94FileMetadata.size
+import com.vitorpamplona.quartz.nip94FileMetadata.thumbhash
 import com.vitorpamplona.quartz.nipA4PublicMessages.PublicMessageEvent
 import com.vitorpamplona.quartz.nipA4PublicMessages.tags.ReceiverTag
 import com.vitorpamplona.quartz.utils.Hex
@@ -486,6 +487,8 @@ class NewPublicMessageViewModel :
                                             ?.let { dims(it) }
                                         state.result.fileHeader.blurHash
                                             ?.let { blurhash(it.blurhash) }
+                                        state.result.fileHeader.thumbHash
+                                            ?.let { thumbhash(it.thumbhash) }
                                         state.result.magnet?.let { magnet(it) }
                                         state.result.uploadedHash?.let { originalHash(it) }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/pictures/PictureCardCompose.kt

@@ -115,6 +115,7 @@ private fun PictureCardImage(
                             dim = it.dimension,
                             uri = uri,
                             mimeType = it.mimeType,
+                            thumbhash = it.thumbhash,
                         )
                     }.toImmutableList(),
             )
@@ -131,7 +132,7 @@ private fun PictureCardImage(
             preloadUrls = listOf(single.url),
             accountViewModel = accountViewModel,
             modifier = mediaSizingModifier(ratio, ContentScale.FillWidth),
-            backdrop = single.blurhash?.let { blurhash -> { BlurhashBackdrop(blurhash, single.description) } },
+            backdrop = (single.thumbhash ?: single.blurhash)?.let { { BlurhashBackdrop(single.blurhash, single.description, single.thumbhash) } },
         ) {
             ZoomableContentView(
                 content = single,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/profile/gallery/GalleryThumb.kt

@@ -86,6 +86,7 @@ fun GalleryThumbnail(
                         dim = noteEvent.dimensions(),
                         uri = null,
                         mimeType = noteEvent.mimeType(),
+                        thumbhash = noteEvent.thumbhash(),
                     )
                 } else {
                     MediaUrlImage(
@@ -97,6 +98,7 @@ fun GalleryThumbnail(
                         dim = noteEvent.dimensions(),
                         uri = null,
                         mimeType = noteEvent.mimeType(),
+                        thumbhash = noteEvent.thumbhash(),
                     )
                 }
             }
@@ -111,6 +113,7 @@ fun GalleryThumbnail(
                     dim = imeta.dimension,
                     uri = null,
                     mimeType = imeta.mimeType,
+                    thumbhash = imeta.thumbhash,
                 )
             }
         } else if (noteEvent is VideoEvent) {
@@ -124,6 +127,7 @@ fun GalleryThumbnail(
                     dim = imeta.dimension,
                     uri = null,
                     mimeType = imeta.mimeType,
+                    thumbhash = imeta.thumbhash,
                 )
             }
         } else {
@@ -210,12 +214,13 @@ fun UrlImageView(
                 when (state) {
                     is AsyncImagePainter.State.Loading,
                     -> {
-                        if (content.blurhash != null) {
+                        if (content.blurhash != null || content.thumbhash != null) {
                             DisplayBlurHash(
                                 content.blurhash,
                                 content.description,
                                 ContentScale.Crop,
                                 defaultModifier,
+                                thumbhash = content.thumbhash,
                             )
                         } else {
                             Box(defaultModifier, contentAlignment = Alignment.Center) {
@@ -243,12 +248,13 @@ fun UrlImageView(
                 }
             }
         } else {
-            if (content.blurhash != null) {
+            if (content.blurhash != null || content.thumbhash != null) {
                 DisplayBlurHash(
                     content.blurhash,
                     content.description,
                     ContentScale.Crop,
                     defaultModifier.clickable { showImage.value = true },
+                    thumbhash = content.thumbhash,
                 )
                 Icon(
                     imageVector = Icons.Default.PlayCircleOutline,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/shorts/VideoCardCompose.kt

@@ -121,6 +121,7 @@ private fun VideoCardImage(
                         dim = imeta.dimension,
                         uri = note.toNostrUri(),
                         mimeType = imeta.mimeType,
+                        thumbhash = imeta.thumbhash,
                     )
                 } else {
                     MediaUrlVideo(
@@ -132,6 +133,7 @@ private fun VideoCardImage(
                         uri = note.toNostrUri(),
                         authorName = note.author?.toBestDisplayName(),
                         mimeType = imeta.mimeType,
+                        thumbhash = imeta.thumbhash,
                     )
                 },
             )
@@ -145,7 +147,7 @@ private fun VideoCardImage(
         preloadUrls = if (isImage) listOf(imeta.url) else emptyList(),
         accountViewModel = accountViewModel,
         modifier = mediaSizingModifier(ratio, ContentScale.FillWidth),
-        backdrop = imeta.blurhash?.let { blurhash -> { BlurhashBackdrop(blurhash, content.description) } },
+        backdrop = (imeta.thumbhash ?: imeta.blurhash)?.let { { BlurhashBackdrop(imeta.blurhash, content.description, imeta.thumbhash) } },
     ) {
         ZoomableContentView(
             content = content,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/threadview/ThreadFeedView.kt

@@ -922,6 +922,7 @@ private fun RenderClassifiedsReaderForThread(
                 dim = it.dimension,
                 uri = note.toNostrUri(),
                 mimeType = it.mimeType,
+                thumbhash = it.thumbhash,
             )
         }
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/video/FileHeaderCardCompose.kt

@@ -104,6 +104,7 @@ private fun FileHeaderCardImage(
     val reasons = remember(note) { collectContentWarningReasons(event) }
     val isImage = remember(note) { event.mimeType()?.startsWith("image/") == true || RichTextParser.isImageUrl(fullUrl) }
     val blurHash = remember(note) { event.blurhash() }
+    val thumbHash = remember(note) { event.thumbhash() }
     val dimensions = remember(note) { event.dimensions() }
 
     val content by remember(note) {
@@ -122,6 +123,7 @@ private fun FileHeaderCardImage(
                     dim = dimensions,
                     uri = uri,
                     mimeType = mimeType,
+                    thumbhash = thumbHash,
                 )
             } else {
                 MediaUrlVideo(
@@ -133,6 +135,7 @@ private fun FileHeaderCardImage(
                     uri = uri,
                     authorName = note.author?.toBestDisplayName(),
                     mimeType = mimeType,
+                    thumbhash = thumbHash,
                 )
             },
         )
@@ -146,7 +149,7 @@ private fun FileHeaderCardImage(
         preloadUrls = if (isImage) listOf(fullUrl) else emptyList(),
         accountViewModel = accountViewModel,
         modifier = mediaSizingModifier(ratio, ContentScale.FillWidth),
-        backdrop = blurHash?.let { blurhash -> { BlurhashBackdrop(blurhash, content.description) } },
+        backdrop = (thumbHash ?: blurHash)?.let { { BlurhashBackdrop(blurHash, content.description, thumbHash) } },
     ) {
         ZoomableContentView(
             content = content,

commons/src/androidMain/kotlin/com/vitorpamplona/amethyst/commons/thumbhash/BitmapUtils.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.thumbhash
+
+import android.graphics.Bitmap
+import com.vitorpamplona.amethyst.commons.blurhash.toPlatformImage
+
+fun Bitmap.toThumbhash(): String = this.toPlatformImage().toThumbhash()

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/richtext/MediaContentModels.kt

@@ -29,6 +29,7 @@ abstract class BaseMediaContent(
     val description: String? = null,
     val dim: DimensionTag? = null,
     val blurhash: String? = null,
+    val thumbhash: String? = null,
 )
 
 @Immutable
@@ -40,7 +41,8 @@ abstract class MediaUrlContent(
     blurhash: String? = null,
     val uri: String? = null,
     val mimeType: String? = null,
-) : BaseMediaContent(description, dim, blurhash)
+    thumbhash: String? = null,
+) : BaseMediaContent(description, dim, blurhash, thumbhash)
 
 @Immutable
 open class MediaUrlImage(
@@ -52,7 +54,8 @@ open class MediaUrlImage(
     uri: String? = null,
     val contentWarning: String? = null,
     mimeType: String? = null,
-) : MediaUrlContent(url, description, hash, dim, blurhash, uri, mimeType)
+    thumbhash: String? = null,
+) : MediaUrlContent(url, description, hash, dim, blurhash, uri, mimeType, thumbhash)
 
 class EncryptedMediaUrlImage(
     url: String,
@@ -66,7 +69,8 @@ class EncryptedMediaUrlImage(
     val encryptionAlgo: String,
     val encryptionKey: ByteArray,
     val encryptionNonce: ByteArray,
-) : MediaUrlImage(url, description, hash, blurhash, dim, uri, contentWarning, mimeType)
+    thumbhash: String? = null,
+) : MediaUrlImage(url, description, hash, blurhash, dim, uri, contentWarning, mimeType, thumbhash)
 
 @Immutable
 open class MediaUrlPdf(
@@ -77,7 +81,8 @@ open class MediaUrlPdf(
     dim: DimensionTag? = null,
     uri: String? = null,
     mimeType: String? = null,
-) : MediaUrlContent(url, description, hash, dim, blurhash, uri, mimeType)
+    thumbhash: String? = null,
+) : MediaUrlContent(url, description, hash, dim, blurhash, uri, mimeType, thumbhash)
 
 @Immutable
 open class MediaUrlVideo(
@@ -91,7 +96,8 @@ open class MediaUrlVideo(
     blurhash: String? = null,
     val contentWarning: String? = null,
     mimeType: String? = null,
-) : MediaUrlContent(url, description, hash, dim, blurhash, uri, mimeType)
+    thumbhash: String? = null,
+) : MediaUrlContent(url, description, hash, dim, blurhash, uri, mimeType, thumbhash)
 
 @Immutable
 class EncryptedMediaUrlVideo(
@@ -108,7 +114,8 @@ class EncryptedMediaUrlVideo(
     val encryptionAlgo: String,
     val encryptionKey: ByteArray,
     val encryptionNonce: ByteArray,
-) : MediaUrlVideo(url, description, hash, dim, uri, artworkUri, authorName, blurhash, contentWarning, mimeType)
+    thumbhash: String? = null,
+) : MediaUrlVideo(url, description, hash, dim, uri, artworkUri, authorName, blurhash, contentWarning, mimeType, thumbhash)
 
 @Immutable
 abstract class MediaPreloadedContent(
@@ -120,7 +127,8 @@ abstract class MediaPreloadedContent(
     blurhash: String? = null,
     val uri: String,
     val id: String? = null,
-) : BaseMediaContent(description, dim, blurhash) {
+    thumbhash: String? = null,
+) : BaseMediaContent(description, dim, blurhash, thumbhash) {
     fun localFileExists() = localFile != null && localFile.exists()
 }
 
@@ -133,7 +141,8 @@ class MediaLocalImage(
     blurhash: String? = null,
     isVerified: Boolean? = null,
     uri: String,
-) : MediaPreloadedContent(localFile, description, mimeType, isVerified, dim, blurhash, uri)
+    thumbhash: String? = null,
+) : MediaPreloadedContent(localFile, description, mimeType, isVerified, dim, blurhash, uri, thumbhash = thumbhash)
 
 @Immutable
 class MediaLocalVideo(
@@ -146,4 +155,5 @@ class MediaLocalVideo(
     uri: String,
     val artworkUri: String? = null,
     val authorName: String? = null,
-) : MediaPreloadedContent(localFile, description, mimeType, isVerified, dim, blurhash, uri)
+    thumbhash: String? = null,
+) : MediaPreloadedContent(localFile, description, mimeType, isVerified, dim, blurhash, uri, thumbhash = thumbhash)

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/richtext/RichTextParser.kt

@@ -32,6 +32,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.BlurhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.DimensionTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.HashSha256Tag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.MimeTypeTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.utils.Log
 import kotlinx.collections.immutable.ImmutableList
 import kotlinx.collections.immutable.persistentListOf
@@ -85,6 +86,7 @@ class RichTextParser {
                 contentWarning = frags[ContentWarningTag.TAG_NAME] ?: tags[ContentWarningTag.TAG_NAME]?.firstOrNull(),
                 uri = callbackUri,
                 mimeType = contentType,
+                thumbhash = frags[ThumbhashTag.TAG_NAME] ?: tags[ThumbhashTag.TAG_NAME]?.firstOrNull(),
             )
         } else if (isVideo) {
             MediaUrlVideo(
@@ -96,6 +98,7 @@ class RichTextParser {
                 contentWarning = frags[ContentWarningTag.TAG_NAME] ?: tags[ContentWarningTag.TAG_NAME]?.firstOrNull(),
                 uri = callbackUri,
                 mimeType = contentType,
+                thumbhash = frags[ThumbhashTag.TAG_NAME] ?: tags[ThumbhashTag.TAG_NAME]?.firstOrNull(),
             )
         } else if (isPdf) {
             MediaUrlPdf(
@@ -106,6 +109,7 @@ class RichTextParser {
                 dim = frags[DimensionTag.TAG_NAME]?.let { DimensionTag.parse(it) } ?: tags[DimensionTag.TAG_NAME]?.firstOrNull()?.let { DimensionTag.parse(it) },
                 uri = callbackUri,
                 mimeType = contentType,
+                thumbhash = frags[ThumbhashTag.TAG_NAME] ?: tags[ThumbhashTag.TAG_NAME]?.firstOrNull(),
             )
         } else {
             null

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/thumbhash/ThumbHashDecoder.kt

@@ -0,0 +1,257 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.thumbhash
+
+import com.vitorpamplona.amethyst.commons.blurhash.PlatformImage
+import kotlin.io.encoding.Base64
+import kotlin.io.encoding.ExperimentalEncodingApi
+import kotlin.math.PI
+import kotlin.math.cos
+import kotlin.math.max
+import kotlin.math.min
+import kotlin.math.round
+
+/**
+ * ThumbHash decoder.
+ *
+ * Port of the reference implementation by Evan Wallace
+ * (https://github.com/evanw/thumbhash, public domain), adapted to Kotlin.
+ */
+object ThumbHashDecoder {
+    /**
+     * Returns width/height. Returns null if the hash is malformed.
+     */
+    fun aspectRatio(hash: ByteArray): Float? {
+        if (hash.size < 5) return null
+        val header = hash[3].toInt() and 0xff
+        val hasAlpha = (hash[2].toInt() and 0x80) != 0
+        val isLandscape = (hash[4].toInt() and 0x80) != 0
+        val lx = if (isLandscape) (if (hasAlpha) 5 else 7) else (header and 7)
+        val ly = if (isLandscape) (header and 7) else (if (hasAlpha) 5 else 7)
+        if (lx == 0 || ly == 0) return null
+        return lx.toFloat() / ly.toFloat()
+    }
+
+    /**
+     * Returns width/height. Returns null if the string is malformed.
+     */
+    @OptIn(ExperimentalEncodingApi::class)
+    fun aspectRatio(base64Hash: String?): Float? {
+        if (base64Hash.isNullOrBlank()) return null
+        return try {
+            aspectRatio(Base64.decode(padBase64(base64Hash)))
+        } catch (_: IllegalArgumentException) {
+            null
+        }
+    }
+
+    data class RGBAImage(
+        val width: Int,
+        val height: Int,
+        val pixels: IntArray,
+    )
+
+    /**
+     * Decode a ThumbHash byte array into ARGB pixels.
+     * Returns null if the hash is malformed.
+     */
+    fun decode(hash: ByteArray): RGBAImage? {
+        if (hash.size < 5) return null
+
+        val b0 = hash[0].toInt() and 0xff
+        val b1 = hash[1].toInt() and 0xff
+        val b2 = hash[2].toInt() and 0xff
+        val b3 = hash[3].toInt() and 0xff
+        val b4 = hash[4].toInt() and 0xff
+        val header24 = b0 or (b1 shl 8) or (b2 shl 16)
+        val header16 = b3 or (b4 shl 8)
+
+        val lDc = (header24 and 63) / 63.0
+        val pDc = ((header24 shr 6) and 63) / 31.5 - 1.0
+        val qDc = ((header24 shr 12) and 63) / 31.5 - 1.0
+        val lScale = ((header24 shr 18) and 31) / 31.0
+        val hasAlpha = (header24 shr 23) and 1 == 1
+        val pScale = ((header16 shr 3) and 63) / 63.0
+        val qScale = ((header16 shr 9) and 63) / 63.0
+        val isLandscape = (header16 shr 15) and 1 == 1
+        val lx = max(3, if (isLandscape) (if (hasAlpha) 5 else 7) else (header16 and 7))
+        val ly = max(3, if (isLandscape) (header16 and 7) else (if (hasAlpha) 5 else 7))
+
+        val aDc: Double
+        val aScale: Double
+        if (hasAlpha) {
+            if (hash.size < 6) return null
+            aDc = (hash[5].toInt() and 15) / 15.0
+            aScale = ((hash[5].toInt() shr 4) and 15) / 15.0
+        } else {
+            aDc = 1.0
+            aScale = 0.0
+        }
+
+        val acStart = if (hasAlpha) 6 else 5
+        var acIndex = 0
+
+        fun readAc(
+            nx: Int,
+            ny: Int,
+            scale: Double,
+        ): DoubleArray {
+            val ac = ArrayList<Double>(nx * ny)
+            var cy = 0
+            while (cy < ny) {
+                var cx = if (cy != 0) 0 else 1
+                while (cx * ny < nx * (ny - cy)) {
+                    val byteIdx = acStart + (acIndex shr 1)
+                    if (byteIdx >= hash.size) return DoubleArray(0)
+                    val shift = (acIndex and 1) shl 2
+                    val q4 = ((hash[byteIdx].toInt() ushr shift) and 15)
+                    ac.add((q4 / 7.5 - 1.0) * scale)
+                    acIndex++
+                    cx++
+                }
+                cy++
+            }
+            return DoubleArray(ac.size) { ac[it] }
+        }
+
+        val lAc = readAc(lx, ly, lScale)
+        val pAc = readAc(3, 3, pScale * 1.25)
+        val qAc = readAc(3, 3, qScale * 1.25)
+        val aAc = if (hasAlpha) readAc(5, 5, aScale) else DoubleArray(0)
+
+        val ratio = lx.toDouble() / ly.toDouble()
+        val w = round(if (ratio > 1) 32.0 else 32.0 * ratio).toInt()
+        val h = round(if (ratio > 1) 32.0 / ratio else 32.0).toInt()
+        val pixels = IntArray(w * h)
+
+        val fxMax = max(lx, if (hasAlpha) 5 else 3)
+        val fyMax = max(ly, if (hasAlpha) 5 else 3)
+        val fx = DoubleArray(fxMax)
+        val fy = DoubleArray(fyMax)
+
+        for (y in 0 until h) {
+            for (x in 0 until w) {
+                var lVal = lDc
+                var pVal = pDc
+                var qVal = qDc
+                var aVal = aDc
+
+                for (cx in 0 until fxMax) fx[cx] = cos(PI / w * (x + 0.5) * cx)
+                for (cy in 0 until fyMax) fy[cy] = cos(PI / h * (y + 0.5) * cy)
+
+                // L
+                run {
+                    var cy = 0
+                    var j = 0
+                    while (cy < ly) {
+                        var cx = if (cy != 0) 0 else 1
+                        val fy2 = fy[cy] * 2.0
+                        while (cx * ly < lx * (ly - cy)) {
+                            lVal += lAc[j] * fx[cx] * fy2
+                            j++
+                            cx++
+                        }
+                        cy++
+                    }
+                }
+
+                // P & Q
+                run {
+                    var cy = 0
+                    var j = 0
+                    while (cy < 3) {
+                        var cx = if (cy != 0) 0 else 1
+                        val fy2 = fy[cy] * 2.0
+                        while (cx < 3 - cy) {
+                            val f = fx[cx] * fy2
+                            pVal += pAc[j] * f
+                            qVal += qAc[j] * f
+                            j++
+                            cx++
+                        }
+                        cy++
+                    }
+                }
+
+                // A
+                if (hasAlpha) {
+                    var cy = 0
+                    var j = 0
+                    while (cy < 5) {
+                        var cx = if (cy != 0) 0 else 1
+                        val fy2 = fy[cy] * 2.0
+                        while (cx < 5 - cy) {
+                            aVal += aAc[j] * fx[cx] * fy2
+                            j++
+                            cx++
+                        }
+                        cy++
+                    }
+                }
+
+                // LPQA → RGB
+                val bCh = lVal - 2.0 / 3.0 * pVal
+                val rCh = (3.0 * lVal - bCh + qVal) / 2.0
+                val gCh = rCh - qVal
+                val rOut = (255.0 * min(1.0, max(0.0, rCh))).let { round(it).toInt() }.coerceIn(0, 255)
+                val gOut = (255.0 * min(1.0, max(0.0, gCh))).let { round(it).toInt() }.coerceIn(0, 255)
+                val bOut = (255.0 * min(1.0, max(0.0, bCh))).let { round(it).toInt() }.coerceIn(0, 255)
+                val aOut = if (hasAlpha) (255.0 * min(1.0, max(0.0, aVal))).let { round(it).toInt() }.coerceIn(0, 255) else 255
+                pixels[x + y * w] = (aOut shl 24) or (rOut shl 16) or (gOut shl 8) or bOut
+            }
+        }
+
+        return RGBAImage(w, h, pixels)
+    }
+
+    /**
+     * Decode a base64-encoded ThumbHash string to ARGB pixels.
+     */
+    @OptIn(ExperimentalEncodingApi::class)
+    fun decode(base64Hash: String?): RGBAImage? {
+        if (base64Hash.isNullOrBlank()) return null
+        return try {
+            decode(Base64.decode(padBase64(base64Hash)))
+        } catch (_: IllegalArgumentException) {
+            null
+        }
+    }
+
+    /**
+     * Decode a ThumbHash string into a [PlatformImage] roughly [targetWidth] wide,
+     * preserving the aspect ratio of the original image.
+     *
+     * Mirrors [com.vitorpamplona.amethyst.commons.blurhash.BlurHashDecoder.decodeKeepAspectRatio]
+     * so existing placeholder pipelines can swap in thumbhash transparently.
+     */
+    fun decodeKeepAspectRatio(
+        hash: String?,
+        targetWidth: Int,
+    ): PlatformImage? {
+        val rgba = decode(hash) ?: return null
+        return PlatformImage.create(rgba.pixels, rgba.width, rgba.height)
+    }
+
+    private fun padBase64(s: String): String {
+        val remainder = s.length % 4
+        return if (remainder == 0) s else s + "=".repeat(4 - remainder)
+    }
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/thumbhash/ThumbHashEncoder.kt

@@ -0,0 +1,218 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.thumbhash
+
+import kotlin.io.encoding.Base64
+import kotlin.math.PI
+import kotlin.math.abs
+import kotlin.math.cos
+import kotlin.math.max
+import kotlin.math.round
+
+/**
+ * ThumbHash encoder.
+ *
+ * Port of the reference implementation by Evan Wallace
+ * (https://github.com/evanw/thumbhash, public domain), adapted to Kotlin.
+ *
+ * Input pixels are ARGB (0xAARRGGBB) to match [com.vitorpamplona.amethyst.commons.blurhash.PlatformImage.getPixels].
+ */
+object ThumbHashEncoder {
+    /**
+     * Encodes an ARGB image to a ThumbHash byte array.
+     *
+     * @param pixels ARGB pixels (0xAARRGGBB), row-by-row; must contain [width] * [height] entries.
+     * @param width Image width in pixels; must be ≤ 100.
+     * @param height Image height in pixels; must be ≤ 100.
+     */
+    fun encode(
+        pixels: IntArray,
+        width: Int,
+        height: Int,
+    ): ByteArray {
+        require(width in 1..100 && height in 1..100) { "ThumbHash input must be ≤100x100 (got ${width}x$height)" }
+        require(pixels.size == width * height) { "pixels.size must equal width * height" }
+
+        // Average color (premultiplied by alpha)
+        var avgR = 0.0
+        var avgG = 0.0
+        var avgB = 0.0
+        var avgA = 0.0
+        for (i in 0 until width * height) {
+            val argb = pixels[i]
+            val alpha = ((argb ushr 24) and 0xff) / 255.0
+            val r = (argb ushr 16) and 0xff
+            val g = (argb ushr 8) and 0xff
+            val b = argb and 0xff
+            avgR += alpha / 255.0 * r
+            avgG += alpha / 255.0 * g
+            avgB += alpha / 255.0 * b
+            avgA += alpha
+        }
+        if (avgA > 0.0) {
+            avgR /= avgA
+            avgG /= avgA
+            avgB /= avgA
+        }
+
+        val hasAlpha = avgA < width * height
+        val lLimit = if (hasAlpha) 5 else 7
+        val lx = max(1, round(lLimit * width.toDouble() / max(width, height)).toInt())
+        val ly = max(1, round(lLimit * height.toDouble() / max(width, height)).toInt())
+
+        val size = width * height
+        val l = DoubleArray(size) // luminance
+        val p = DoubleArray(size) // yellow - blue
+        val q = DoubleArray(size) // red - green
+        val a = DoubleArray(size) // alpha
+
+        // Convert ARGB to LPQA, composited over the average color
+        for (i in 0 until size) {
+            val argb = pixels[i]
+            val alpha = ((argb ushr 24) and 0xff) / 255.0
+            val rPx = (argb ushr 16) and 0xff
+            val gPx = (argb ushr 8) and 0xff
+            val bPx = argb and 0xff
+            val r = avgR * (1 - alpha) + alpha / 255.0 * rPx
+            val g = avgG * (1 - alpha) + alpha / 255.0 * gPx
+            val b = avgB * (1 - alpha) + alpha / 255.0 * bPx
+            l[i] = (r + g + b) / 3.0
+            p[i] = (r + g) / 2.0 - b
+            q[i] = r - g
+            a[i] = alpha
+        }
+
+        val lEnc = encodeChannel(l, width, height, max(3, lx), max(3, ly))
+        val pEnc = encodeChannel(p, width, height, 3, 3)
+        val qEnc = encodeChannel(q, width, height, 3, 3)
+        val aEnc = if (hasAlpha) encodeChannel(a, width, height, 5, 5) else null
+
+        val isLandscape = width > height
+        val lCount = if (isLandscape) ly else lx
+        val hasAlphaBit = if (hasAlpha) 1 else 0
+        val isLandscapeBit = if (isLandscape) 1 else 0
+
+        val header24 =
+            round(63.0 * lEnc.dc).toInt() or
+                (round(31.5 + 31.5 * pEnc.dc).toInt() shl 6) or
+                (round(31.5 + 31.5 * qEnc.dc).toInt() shl 12) or
+                (round(31.0 * lEnc.scale).toInt() shl 18) or
+                (hasAlphaBit shl 23)
+        val header16 =
+            lCount or
+                (round(63.0 * pEnc.scale).toInt() shl 3) or
+                (round(63.0 * qEnc.scale).toInt() shl 9) or
+                (isLandscapeBit shl 15)
+
+        val acChannels = if (hasAlpha) listOf(lEnc.ac, pEnc.ac, qEnc.ac, aEnc!!.ac) else listOf(lEnc.ac, pEnc.ac, qEnc.ac)
+        val totalAc = acChannels.sumOf { it.size }
+        val acStart = if (hasAlpha) 6 else 5
+        val hashSize = acStart + ((totalAc + 1) / 2)
+        val hash = ByteArray(hashSize)
+        hash[0] = (header24 and 0xff).toByte()
+        hash[1] = ((header24 ushr 8) and 0xff).toByte()
+        hash[2] = ((header24 ushr 16) and 0xff).toByte()
+        hash[3] = (header16 and 0xff).toByte()
+        hash[4] = ((header16 ushr 8) and 0xff).toByte()
+
+        if (hasAlpha) {
+            val aDcQ = round(15.0 * aEnc!!.dc).toInt() and 0xf
+            val aScaleQ = round(15.0 * aEnc.scale).toInt() and 0xf
+            hash[5] = (aDcQ or (aScaleQ shl 4)).toByte()
+        }
+
+        var acIndex = 0
+        for (ac in acChannels) {
+            for (f in ac) {
+                val q4 = round(15.0 * f).toInt() and 0xf
+                val byteIdx = acStart + (acIndex shr 1)
+                val shift = (acIndex and 1) shl 2
+                hash[byteIdx] = (hash[byteIdx].toInt() or (q4 shl shift)).toByte()
+                acIndex++
+            }
+        }
+
+        return hash
+    }
+
+    /**
+     * Encodes an ARGB image to a base64 ThumbHash string (no padding).
+     */
+    @OptIn(kotlin.io.encoding.ExperimentalEncodingApi::class)
+    fun encodeToBase64(
+        pixels: IntArray,
+        width: Int,
+        height: Int,
+    ): String = Base64.encode(encode(pixels, width, height)).trimEnd('=')
+
+    private data class ChannelEncoded(
+        val dc: Double,
+        val ac: DoubleArray,
+        val scale: Double,
+    )
+
+    private fun encodeChannel(
+        channel: DoubleArray,
+        w: Int,
+        h: Int,
+        nx: Int,
+        ny: Int,
+    ): ChannelEncoded {
+        var dc = 0.0
+        var scale = 0.0
+        val acList = ArrayList<Double>((nx * ny))
+        val fx = DoubleArray(w)
+
+        var cy = 0
+        while (cy < ny) {
+            var cx = 0
+            while (cx * ny < nx * (ny - cy)) {
+                var f = 0.0
+                for (x in 0 until w) {
+                    fx[x] = cos(PI / w * cx * (x + 0.5))
+                }
+                for (y in 0 until h) {
+                    val fy = cos(PI / h * cy * (y + 0.5))
+                    for (x in 0 until w) {
+                        f += channel[x + y * w] * fx[x] * fy
+                    }
+                }
+                f /= (w * h).toDouble()
+                if (cx != 0 || cy != 0) {
+                    acList.add(f)
+                    if (abs(f) > scale) scale = abs(f)
+                } else {
+                    dc = f
+                }
+                cx++
+            }
+            cy++
+        }
+
+        val ac = DoubleArray(acList.size) { acList[it] }
+        if (scale != 0.0) {
+            for (i in ac.indices) {
+                ac[i] = 0.5 + 0.5 / scale * ac[i]
+            }
+        }
+        return ChannelEncoded(dc, ac, scale)
+    }
+}

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/thumbhash/ThumbHashEncoderExt.kt

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.thumbhash
+
+import com.vitorpamplona.amethyst.commons.blurhash.PlatformImage
+
+/**
+ * Encodes this [PlatformImage] to a base64 ThumbHash string (no padding).
+ *
+ * ThumbHash is specified at ≤100x100. Larger images are downscaled first.
+ */
+fun PlatformImage.toThumbhash(): String {
+    val source =
+        if (width > 100 || height > 100) {
+            val aspect = width.toDouble() / height.toDouble()
+            val scaled =
+                if (width >= height) {
+                    val w = 100
+                    val h = (100.0 / aspect).toInt().coerceAtLeast(1)
+                    this.scale(w, h)
+                } else {
+                    val h = 100
+                    val w = (100.0 * aspect).toInt().coerceAtLeast(1)
+                    this.scale(w, h)
+                }
+            scaled
+        } else {
+            this
+        }
+
+    val pixels = IntArray(source.width * source.height)
+    source.getPixels(pixels, 0, source.width, 0, 0, source.width, source.height)
+    return ThumbHashEncoder.encodeToBase64(pixels, source.width, source.height)
+}

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/ThumbHashTest.kt

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons
+
+import com.vitorpamplona.amethyst.commons.thumbhash.ThumbHashDecoder
+import com.vitorpamplona.amethyst.commons.thumbhash.ThumbHashEncoder
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class ThumbHashTest {
+    @Test
+    fun `encode and decode a solid color produces a hash with matching aspect`() {
+        val w = 32
+        val h = 24
+        val pixels = IntArray(w * h) { 0xFFFF8040.toInt() } // opaque warm orange
+
+        val hashBytes = ThumbHashEncoder.encode(pixels, w, h)
+        assertTrue("hash should have at least header bytes", hashBytes.size >= 5)
+
+        val decoded = ThumbHashDecoder.decode(hashBytes)
+        assertNotNull(decoded)
+        decoded!!
+        assertTrue("decoded width should be positive", decoded.width > 0)
+        assertTrue("decoded height should be positive", decoded.height > 0)
+
+        val originalRatio = w.toFloat() / h.toFloat()
+        val decodedRatio = decoded.width.toFloat() / decoded.height.toFloat()
+        // ThumbHash loses some precision, but landscape vs portrait should be preserved.
+        assertTrue(
+            "decoded ratio ($decodedRatio) should be on the same side of 1 as original ($originalRatio)",
+            (originalRatio > 1f) == (decodedRatio > 1f) || originalRatio == decodedRatio,
+        )
+    }
+
+    @Test
+    fun `base64 round-trip preserves decoded dimensions`() {
+        val w = 40
+        val h = 40
+        // A simple gradient so the image isn't entirely flat.
+        val pixels =
+            IntArray(w * h) { i ->
+                val x = i % w
+                val y = i / w
+                val r = (x * 255 / (w - 1))
+                val g = (y * 255 / (h - 1))
+                (0xFF shl 24) or (r shl 16) or (g shl 8) or 0x40
+            }
+
+        val encoded = ThumbHashEncoder.encodeToBase64(pixels, w, h)
+        assertTrue("base64 string should be non-empty", encoded.isNotEmpty())
+        assertTrue("base64 string should not contain padding", !encoded.contains('='))
+
+        val viaBase64 = ThumbHashDecoder.decode(encoded)
+        assertNotNull(viaBase64)
+        viaBase64!!
+
+        val viaBytes = ThumbHashDecoder.decode(ThumbHashEncoder.encode(pixels, w, h))
+        assertNotNull(viaBytes)
+        viaBytes!!
+
+        assertEquals("base64 path and raw path should agree on width", viaBytes.width, viaBase64.width)
+        assertEquals("base64 path and raw path should agree on height", viaBytes.height, viaBase64.height)
+    }
+
+    @Test
+    fun `decoding a malformed hash returns null`() {
+        assertEquals(null, ThumbHashDecoder.decode(ByteArray(3)))
+        assertEquals(null, ThumbHashDecoder.decode(null as String?))
+        assertEquals(null, ThumbHashDecoder.decode(""))
+    }
+}

commons/src/jvmMain/kotlin/com/vitorpamplona/amethyst/commons/thumbhash/BitmapUtils.jvm.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.thumbhash
+
+import com.vitorpamplona.amethyst.commons.blurhash.toPlatformImage
+import java.awt.image.BufferedImage
+
+fun BufferedImage.toThumbhash(): String = this.toPlatformImage().toThumbhash()

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/service/images/DesktopImageLoaderSetup.kt

@@ -60,8 +60,10 @@ object DesktopImageLoaderSetup {
                 add(SkiaGifDecoder.Factory())
                 add(DesktopBase64Fetcher.Factory)
                 add(DesktopBlurHashFetcher.Factory)
+                add(DesktopThumbHashFetcher.Factory)
                 add(DesktopBase64Fetcher.BKeyer)
                 add(DesktopBlurHashFetcher.BKeyer)
+                add(DesktopThumbHashFetcher.TKeyer)
             }.build()
 
     private fun newMemoryCache(): MemoryCache {

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/service/images/DesktopThumbHashFetcher.kt

@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.desktop.service.images
+
+import androidx.compose.runtime.Stable
+import coil3.ImageLoader
+import coil3.asImage
+import coil3.decode.DataSource
+import coil3.fetch.FetchResult
+import coil3.fetch.Fetcher
+import coil3.fetch.ImageFetchResult
+import coil3.key.Keyer
+import coil3.request.Options
+import com.vitorpamplona.amethyst.commons.blurhash.toBufferedImage
+import com.vitorpamplona.amethyst.commons.thumbhash.ThumbHashDecoder
+
+data class ThumbhashWrapper(
+    val thumbhash: String,
+)
+
+@Stable
+class DesktopThumbHashFetcher(
+    private val data: ThumbhashWrapper,
+) : Fetcher {
+    override suspend fun fetch(): FetchResult? {
+        val hash = data.thumbhash
+        val platformImage = ThumbHashDecoder.decodeKeepAspectRatio(hash, 25) ?: return null
+        val bufferedImage = platformImage.toBufferedImage()
+        val bitmap = bufferedImageToSkiaBitmap(bufferedImage)
+
+        return ImageFetchResult(
+            image = bitmap.asImage(true),
+            isSampled = false,
+            dataSource = DataSource.MEMORY,
+        )
+    }
+
+    object Factory : Fetcher.Factory<ThumbhashWrapper> {
+        override fun create(
+            data: ThumbhashWrapper,
+            options: Options,
+            imageLoader: ImageLoader,
+        ): Fetcher = DesktopThumbHashFetcher(data)
+    }
+
+    object TKeyer : Keyer<ThumbhashWrapper> {
+        override fun key(
+            data: ThumbhashWrapper,
+            options: Options,
+        ): String = data.thumbhash
+    }
+}
+
+/**
+ * Pick the best Coil model for a media placeholder on Desktop.
+ *
+ * Prefers [ThumbhashWrapper] when a thumbhash is available (better quality, preserves aspect ratio
+ * and alpha) and falls back to [BlurhashWrapper] when only a blurhash is present.
+ */
+fun placeholderModel(
+    thumbhash: String?,
+    blurhash: String?,
+): Any? =
+    when {
+        !thumbhash.isNullOrEmpty() -> ThumbhashWrapper(thumbhash)
+        !blurhash.isNullOrEmpty() -> BlurhashWrapper(blurhash)
+        else -> null
+    }

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/service/upload/DesktopMediaMetadata.kt

@@ -22,6 +22,7 @@ package com.vitorpamplona.amethyst.desktop.service.upload
 
 import com.vitorpamplona.amethyst.commons.blurhash.toBlurhash
 import com.vitorpamplona.amethyst.commons.blurhash.toPlatformImage
+import com.vitorpamplona.amethyst.commons.thumbhash.toThumbhash
 import com.vitorpamplona.quartz.nip01Core.core.toHexKey
 import com.vitorpamplona.quartz.utils.sha256.sha256
 import java.io.File
@@ -34,6 +35,7 @@ data class MediaMetadata(
     val width: Int? = null,
     val height: Int? = null,
     val blurhash: String? = null,
+    val thumbhash: String? = null,
 )
 
 object DesktopMediaMetadata {
@@ -44,6 +46,7 @@ object DesktopMediaMetadata {
         var width: Int? = null
         var height: Int? = null
         var blurhash: String? = null
+        var thumbhash: String? = null
 
         if (mimeType.startsWith("image/")) {
             try {
@@ -51,7 +54,9 @@ object DesktopMediaMetadata {
                 if (image != null) {
                     width = image.width
                     height = image.height
-                    blurhash = image.toPlatformImage().toBlurhash()
+                    val platformImage = image.toPlatformImage()
+                    blurhash = runCatching { platformImage.toBlurhash() }.getOrNull()
+                    thumbhash = runCatching { platformImage.toThumbhash() }.getOrNull()
                 }
             } catch (_: Exception) {
             }
@@ -64,6 +69,7 @@ object DesktopMediaMetadata {
             width = width,
             height = height,
             blurhash = blurhash,
+            thumbhash = thumbhash,
         )
     }
 

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/ComposeNoteDialog.kt

@@ -358,6 +358,7 @@ private fun buildIMetaTags(results: List<UploadResult>): List<IMetaTag> =
             props["dim"] = listOf("${meta.width}x${meta.height}")
         }
         meta.blurhash?.let { props["blurhash"] = listOf(it) }
+        meta.thumbhash?.let { props["thumbhash"] = listOf(it) }
         IMetaTag(url = url, properties = props)
     }
 
@@ -460,6 +461,7 @@ private fun buildPictureMetas(results: List<UploadResult>): List<com.vitorpamplo
                 },
             hash = meta.sha256,
             size = meta.size.toInt(),
+            thumbhash = meta.thumbhash,
         )
     }
 

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/chats/ChatPane.kt

@@ -825,6 +825,7 @@ private suspend fun sendEncryptedFiles(
                         null
                     },
                 blurhash = result.metadata.blurhash,
+                thumbhash = result.metadata.thumbhash,
                 originalHash = result.metadata.sha256,
             )
         account.sendNip17EncryptedFile(template)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/experimental/nip95/header/FileStorageHeaderEvent.kt

@@ -43,6 +43,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 import com.vitorpamplona.quartz.utils.TimeUtils
 
@@ -75,6 +76,8 @@ class FileStorageHeaderEvent(
 
     fun blurhash() = tags.firstNotNullOfOrNull(BlurhashTag::parse)
 
+    fun thumbhash() = tags.firstNotNullOfOrNull(ThumbhashTag::parse)
+
     fun image() = tags.firstNotNullOfOrNull(ImageTag::parse)
 
     fun thumb() = tags.firstNotNullOfOrNull(ThumbTag::parse)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/experimental/nip95/header/TagArrayBuilderExt.kt

@@ -33,6 +33,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 
 fun TagArrayBuilder<FileStorageHeaderEvent>.mimeType(mimeType: String) = add(MimeTypeTag.assemble(mimeType))
@@ -45,6 +46,8 @@ fun TagArrayBuilder<FileStorageHeaderEvent>.dimension(dim: DimensionTag) = add(D
 
 fun TagArrayBuilder<FileStorageHeaderEvent>.blurhash(blurhash: String) = add(BlurhashTag.assemble(blurhash))
 
+fun TagArrayBuilder<FileStorageHeaderEvent>.thumbhash(thumbhash: String) = add(ThumbhashTag.assemble(thumbhash))
+
 fun TagArrayBuilder<FileStorageHeaderEvent>.torrentInfohash(hash: String) = add(TorrentInfoHash.assemble(hash))
 
 fun TagArrayBuilder<FileStorageHeaderEvent>.magnet(magnetUri: String) = add(MagnetTag.assemble(magnetUri))

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/experimental/profileGallery/ProfileGalleryEntryEvent.kt

@@ -39,6 +39,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.UrlTag
 import com.vitorpamplona.quartz.utils.TimeUtils
@@ -70,6 +71,8 @@ class ProfileGalleryEntryEvent(
 
     fun blurhash() = tags.firstNotNullOfOrNull(BlurhashTag::parse)
 
+    fun thumbhash() = tags.firstNotNullOfOrNull(ThumbhashTag::parse)
+
     fun image() = tags.firstNotNullOfOrNull(ImageTag::parse)
 
     fun thumb() = tags.firstNotNullOfOrNull(ThumbTag::parse)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/experimental/profileGallery/TagArrayBuilderExt.kt

@@ -36,6 +36,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.UrlTag
 
@@ -51,6 +52,8 @@ fun TagArrayBuilder<ProfileGalleryEntryEvent>.dimension(dim: DimensionTag) = add
 
 fun TagArrayBuilder<ProfileGalleryEntryEvent>.blurhash(blurhash: String) = add(BlurhashTag.assemble(blurhash))
 
+fun TagArrayBuilder<ProfileGalleryEntryEvent>.thumbhash(thumbhash: String) = add(ThumbhashTag.assemble(thumbhash))
+
 fun TagArrayBuilder<ProfileGalleryEntryEvent>.originalHash(hash: HexKey) = add(OriginalHashTag.assemble(hash))
 
 fun TagArrayBuilder<ProfileGalleryEntryEvent>.torrentInfohash(hash: String) = add(TorrentInfoHash.assemble(hash))

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mip04EncryptedMedia/Mip04IMetaTag.kt

@@ -166,6 +166,7 @@ fun buildMip04IMetaTag(
     nonce: ByteArray,
     dimensions: String? = null,
     blurhash: String? = null,
+    thumbhash: String? = null,
 ): IMetaTag =
     IMetaTagBuilder(url)
         .apply {
@@ -176,4 +177,5 @@ fun buildMip04IMetaTag(
             add(Mip04Fields.VERSION, Mip04MediaEncryption.VERSION)
             dimensions?.let { add(Mip04Fields.DIMENSIONS, it) }
             blurhash?.let { add(Mip04Fields.BLURHASH, it) }
+            thumbhash?.let { add(Mip04Fields.THUMBHASH, it) }
         }.build()

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip17Dm/files/ChatMessageEncryptedFileHeaderEvent.kt

@@ -39,6 +39,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.DimensionTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.HashSha256Tag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.OriginalHashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.utils.TimeUtils
 import com.vitorpamplona.quartz.utils.ciphers.AESGCM
 
@@ -65,6 +66,8 @@ class ChatMessageEncryptedFileHeaderEvent(
 
     fun blurhash() = tags.firstNotNullOfOrNull(BlurhashTag::parse)
 
+    fun thumbhash() = tags.firstNotNullOfOrNull(ThumbhashTag::parse)
+
     fun originalHash() = tags.firstNotNullOfOrNull(OriginalHashTag::parse)
 
     fun algo() = tags.firstNotNullOfOrNull(EncryptionAlgo::parse)
@@ -87,6 +90,7 @@ class ChatMessageEncryptedFileHeaderEvent(
             size: Int? = null,
             dimension: DimensionTag? = null,
             blurhash: String? = null,
+            thumbhash: String? = null,
             originalHash: String? = null,
             magnetUri: String? = null,
             torrentInfoHash: String? = null,
@@ -108,6 +112,7 @@ class ChatMessageEncryptedFileHeaderEvent(
             mimeType?.let { mimeType(it) }
             dimension?.let { dimension(it) }
             blurhash?.let { blurhash(it) }
+            thumbhash?.let { thumbhash(it) }
             originalHash?.let { originalHash(it) }
             magnetUri?.let { magnet(it) }
             torrentInfoHash?.let { torrentInfohash(it) }

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip17Dm/files/TagArrayBuilderExt.kt

@@ -44,6 +44,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 
 fun TagArrayBuilder<ChatMessageEncryptedFileHeaderEvent>.reply(msg: MarkedETag) = add(msg.toTagArray())
@@ -70,6 +71,8 @@ fun TagArrayBuilder<ChatMessageEncryptedFileHeaderEvent>.dimension(dim: Dimensio
 
 fun TagArrayBuilder<ChatMessageEncryptedFileHeaderEvent>.blurhash(blurhash: String) = add(BlurhashTag.assemble(blurhash))
 
+fun TagArrayBuilder<ChatMessageEncryptedFileHeaderEvent>.thumbhash(thumbhash: String) = add(ThumbhashTag.assemble(thumbhash))
+
 fun TagArrayBuilder<ChatMessageEncryptedFileHeaderEvent>.originalHash(hash: HexKey) = add(OriginalHashTag.assemble(hash))
 
 fun TagArrayBuilder<ChatMessageEncryptedFileHeaderEvent>.torrentInfohash(hash: String) = add(TorrentInfoHash.assemble(hash))

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip68Picture/IMetaTagBuilderExt.kt

@@ -37,6 +37,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 
 /**
@@ -56,6 +57,8 @@ fun IMetaTagBuilder.dims(dims: DimensionTag) = add(DimensionTag.TAG_NAME, dims.t
 
 fun IMetaTagBuilder.blurhash(blurhash: String) = add(BlurhashTag.TAG_NAME, blurhash)
 
+fun IMetaTagBuilder.thumbhash(thumbhash: String) = add(ThumbhashTag.TAG_NAME, thumbhash)
+
 fun IMetaTagBuilder.originalHash(originalHash: String) = add(OriginalHashTag.TAG_NAME, originalHash)
 
 fun IMetaTagBuilder.torrent(uri: String) = add(TorrentInfoHash.TAG_NAME, uri)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip68Picture/IMetaTagExt.kt

@@ -36,6 +36,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 
 /**
@@ -55,6 +56,8 @@ fun IMetaTag.dims() = properties.get(DimensionTag.TAG_NAME)
 
 fun IMetaTag.blurhash() = properties.get(BlurhashTag.TAG_NAME)
 
+fun IMetaTag.thumbhash() = properties.get(ThumbhashTag.TAG_NAME)
+
 fun IMetaTag.originalHash() = properties.get(OriginalHashTag.TAG_NAME)
 
 fun IMetaTag.torrent() = properties.get(TorrentInfoHash.TAG_NAME)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip68Picture/PictureMeta.kt

@@ -36,6 +36,7 @@ data class PictureMeta(
     val service: String? = null,
     val fallback: List<String> = emptyList(),
     val annotations: List<UserAnnotationTag> = emptyList(),
+    val thumbhash: String? = null,
 ) {
     fun toIMetaArray(): Array<String> =
         IMetaTagBuilder(url)
@@ -46,6 +47,7 @@ data class PictureMeta(
                 size?.let { size(it) }
                 dimension?.let { dims(it) }
                 blurhash?.let { blurhash(it) }
+                thumbhash?.let { thumbhash(it) }
                 service?.let { service(it) }
                 fallback.forEach { fallback(it) }
                 annotations.forEach { userAnnotations(it) }
@@ -55,16 +57,17 @@ data class PictureMeta(
     companion object {
         fun parse(iMeta: IMetaTag): PictureMeta =
             PictureMeta(
-                iMeta.url,
+                url = iMeta.url,
-                iMeta.mimeType()?.firstOrNull(),
+                mimeType = iMeta.mimeType()?.firstOrNull(),
-                iMeta.blurhash()?.firstOrNull(),
+                blurhash = iMeta.blurhash()?.firstOrNull(),
-                iMeta.dims()?.firstOrNull()?.let { DimensionTag.parse(it) },
+                dimension = iMeta.dims()?.firstOrNull()?.let { DimensionTag.parse(it) },
-                iMeta.alt()?.firstOrNull(),
+                alt = iMeta.alt()?.firstOrNull(),
-                iMeta.hash()?.firstOrNull(),
+                hash = iMeta.hash()?.firstOrNull(),
-                iMeta.size()?.firstOrNull()?.toIntOrNull(),
+                size = iMeta.size()?.firstOrNull()?.toIntOrNull(),
-                iMeta.service()?.firstOrNull(),
+                service = iMeta.service()?.firstOrNull(),
-                iMeta.fallback() ?: emptyList(),
+                fallback = iMeta.fallback() ?: emptyList(),
-                iMeta.userAnnotations() ?: emptyList(),
+                annotations = iMeta.userAnnotations() ?: emptyList(),
+                thumbhash = iMeta.thumbhash()?.firstOrNull(),
             )
     }
 }

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip68Picture/TagArrayBuilderExt.kt

@@ -39,7 +39,8 @@ fun TagArrayBuilder<PictureEvent>.pictureIMeta(
     hash: String? = null,
     size: Int? = null,
     alt: String? = null,
-) = pictureIMeta(PictureMeta(url, mimeType, blurhash, dimension, alt, hash, size))
+    thumbhash: String? = null,
+) = pictureIMeta(PictureMeta(url, mimeType, blurhash, dimension, alt, hash, size, thumbhash = thumbhash))
 
 fun TagArrayBuilder<PictureEvent>.pictureIMeta(imeta: PictureMeta): TagArrayBuilder<PictureEvent> {
     add(imeta.toIMetaArray())

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip71Video/IMetaTagBuilderExt.kt

@@ -36,6 +36,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 
 /**
@@ -55,6 +56,8 @@ fun IMetaTagBuilder.dims(dims: DimensionTag) = add(DimensionTag.TAG_NAME, dims.t
 
 fun IMetaTagBuilder.blurhash(blurhash: String) = add(BlurhashTag.TAG_NAME, blurhash)
 
+fun IMetaTagBuilder.thumbhash(thumbhash: String) = add(ThumbhashTag.TAG_NAME, thumbhash)
+
 fun IMetaTagBuilder.originalHash(originalHash: String) = add(OriginalHashTag.TAG_NAME, originalHash)
 
 fun IMetaTagBuilder.torrent(uri: String) = add(TorrentInfoHash.TAG_NAME, uri)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip71Video/IMetaTagExt.kt

@@ -35,6 +35,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 
 /**
@@ -54,6 +55,8 @@ fun IMetaTag.dims() = properties.get(DimensionTag.TAG_NAME)
 
 fun IMetaTag.blurhash() = properties.get(BlurhashTag.TAG_NAME)
 
+fun IMetaTag.thumbhash() = properties.get(ThumbhashTag.TAG_NAME)
+
 fun IMetaTag.originalHash() = properties.get(OriginalHashTag.TAG_NAME)
 
 fun IMetaTag.torrent() = properties.get(TorrentInfoHash.TAG_NAME)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip71Video/TagArrayBuilderExt.kt

@@ -43,7 +43,8 @@ fun <T : VideoEvent> TagArrayBuilder<T>.videoIMeta(
     hash: String? = null,
     size: Int? = null,
     alt: String? = null,
-) = videoIMeta(VideoMeta(url, mimeType, blurhash, dimension, alt, hash, size))
+    thumbhash: String? = null,
+) = videoIMeta(VideoMeta(url, mimeType, blurhash, dimension, alt, hash, size, thumbhash = thumbhash))
 
 fun <T : VideoEvent> TagArrayBuilder<T>.videoIMeta(imeta: VideoMeta) = add(imeta.toIMetaArray())
 

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip71Video/VideoMeta.kt

@@ -35,6 +35,7 @@ data class VideoMeta(
     val service: String? = null,
     val fallback: List<String> = emptyList(),
     val image: List<String> = emptyList(),
+    val thumbhash: String? = null,
 ) {
     fun toIMetaArray(): Array<String> =
         IMetaTagBuilder(url)
@@ -45,6 +46,7 @@ data class VideoMeta(
                 size?.let { size(it) }
                 dimension?.let { dims(it) }
                 blurhash?.let { blurhash(it) }
+                thumbhash?.let { thumbhash(it) }
                 service?.let { service(it) }
                 fallback.forEach { fallback(it) }
                 image.forEach { image(it) }
@@ -54,16 +56,17 @@ data class VideoMeta(
     companion object {
         fun parse(iMeta: IMetaTag): VideoMeta =
             VideoMeta(
-                iMeta.url,
+                url = iMeta.url,
-                iMeta.mimeType()?.firstOrNull(),
+                mimeType = iMeta.mimeType()?.firstOrNull(),
-                iMeta.blurhash()?.firstOrNull(),
+                blurhash = iMeta.blurhash()?.firstOrNull(),
-                iMeta.dims()?.firstOrNull()?.let { DimensionTag.parse(it) },
+                dimension = iMeta.dims()?.firstOrNull()?.let { DimensionTag.parse(it) },
-                iMeta.alt()?.firstOrNull(),
+                alt = iMeta.alt()?.firstOrNull(),
-                iMeta.hash()?.firstOrNull(),
+                hash = iMeta.hash()?.firstOrNull(),
-                iMeta.size()?.firstOrNull()?.toIntOrNull(),
+                size = iMeta.size()?.firstOrNull()?.toIntOrNull(),
-                iMeta.service()?.firstOrNull(),
+                service = iMeta.service()?.firstOrNull(),
-                iMeta.fallback() ?: emptyList(),
+                fallback = iMeta.fallback() ?: emptyList(),
-                iMeta.image() ?: emptyList(),
+                image = iMeta.image() ?: emptyList(),
+                thumbhash = iMeta.thumbhash()?.firstOrNull(),
             )
     }
 }

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip94FileMetadata/FileHeaderEvent.kt

@@ -38,6 +38,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.UrlTag
 import com.vitorpamplona.quartz.utils.TimeUtils
@@ -69,6 +70,8 @@ class FileHeaderEvent(
 
     fun blurhash() = tags.firstNotNullOfOrNull(BlurhashTag::parse)
 
+    fun thumbhash() = tags.firstNotNullOfOrNull(ThumbhashTag::parse)
+
     fun image() = tags.firstNotNullOfOrNull(ImageTag::parse)
 
     fun thumb() = tags.firstNotNullOfOrNull(ThumbTag::parse)
@@ -106,6 +109,7 @@ class FileHeaderEvent(
             size: Int? = null,
             dimension: DimensionTag? = null,
             blurhash: String? = null,
+            thumbhash: String? = null,
             originalHash: String? = null,
             magnetUri: String? = null,
             torrentInfoHash: String? = null,
@@ -120,6 +124,7 @@ class FileHeaderEvent(
             mimeType?.let { mimeType(it) }
             dimension?.let { dimension(it) }
             blurhash?.let { blurhash(it) }
+            thumbhash?.let { thumbhash(it) }
             originalHash?.let { originalHash(it) }
             magnetUri?.let { magnet(it) }
             torrentInfoHash?.let { torrentInfohash(it) }

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip94FileMetadata/IMetaTagBuilderExt.kt

@@ -36,6 +36,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 
 /**
@@ -55,6 +56,8 @@ fun IMetaTagBuilder.dims(dims: DimensionTag) = add(DimensionTag.TAG_NAME, dims.t
 
 fun IMetaTagBuilder.blurhash(blurhash: String) = add(BlurhashTag.TAG_NAME, blurhash)
 
+fun IMetaTagBuilder.thumbhash(thumbhash: String) = add(ThumbhashTag.TAG_NAME, thumbhash)
+
 fun IMetaTagBuilder.originalHash(originalHash: String) = add(OriginalHashTag.TAG_NAME, originalHash)
 
 fun IMetaTagBuilder.torrent(uri: String) = add(TorrentInfoHash.TAG_NAME, uri)

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip94FileMetadata/TagArrayBuilderExt.kt

@@ -34,6 +34,7 @@ import com.vitorpamplona.quartz.nip94FileMetadata.tags.ServiceTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SizeTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.SummaryTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbTag
+import com.vitorpamplona.quartz.nip94FileMetadata.tags.ThumbhashTag
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.TorrentInfoHash
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.UrlTag
 
@@ -49,6 +50,8 @@ fun TagArrayBuilder<FileHeaderEvent>.dimension(dim: DimensionTag) = add(Dimensio
 
 fun TagArrayBuilder<FileHeaderEvent>.blurhash(blurhash: String) = add(BlurhashTag.assemble(blurhash))
 
+fun TagArrayBuilder<FileHeaderEvent>.thumbhash(thumbhash: String) = add(ThumbhashTag.assemble(thumbhash))
+
 fun TagArrayBuilder<FileHeaderEvent>.originalHash(hash: HexKey) = add(OriginalHashTag.assemble(hash))
 
 fun TagArrayBuilder<FileHeaderEvent>.torrentInfohash(hash: String) = add(TorrentInfoHash.assemble(hash))

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip94FileMetadata/tags/ThumbhashTag.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.quartz.nip94FileMetadata.tags
+
+import com.vitorpamplona.quartz.nip01Core.core.has
+import com.vitorpamplona.quartz.utils.ensure
+
+class ThumbhashTag {
+    companion object {
+        const val TAG_NAME = "thumbhash"
+
+        fun parse(tag: Array<String>): String? {
+            ensure(tag.has(1)) { return null }
+            ensure(tag[0] == TAG_NAME) { return null }
+            ensure(tag[1].isNotEmpty()) { return null }
+            return tag[1]
+        }
+
+        fun assemble(hash: String) = arrayOf(TAG_NAME, hash)
+    }
+}

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip99Classifieds/ProductImageMeta.kt

@@ -26,6 +26,7 @@ import com.vitorpamplona.quartz.nip68Picture.dims
 import com.vitorpamplona.quartz.nip68Picture.hash
 import com.vitorpamplona.quartz.nip68Picture.mimeType
 import com.vitorpamplona.quartz.nip68Picture.size
+import com.vitorpamplona.quartz.nip68Picture.thumbhash
 import com.vitorpamplona.quartz.nip92IMeta.IMetaTag
 import com.vitorpamplona.quartz.nip92IMeta.IMetaTagBuilder
 import com.vitorpamplona.quartz.nip94FileMetadata.tags.DimensionTag
@@ -38,6 +39,7 @@ data class ProductImageMeta(
     val alt: String? = null,
     val hash: String? = null,
     val size: Int? = null,
+    val thumbhash: String? = null,
 ) {
     fun toIMeta(): IMetaTag =
         IMetaTagBuilder(url)
@@ -48,6 +50,7 @@ data class ProductImageMeta(
                 size?.let { size(it) }
                 dimension?.let { dims(it) }
                 blurhash?.let { blurhash(it) }
+                thumbhash?.let { thumbhash(it) }
             }.build()
 
     fun toIMetaArray(): Array<String> = toIMeta().toTagArray()
@@ -55,13 +58,14 @@ data class ProductImageMeta(
     companion object {
         fun parse(iMeta: IMetaTag): ProductImageMeta =
             ProductImageMeta(
-                iMeta.url,
+                url = iMeta.url,
-                iMeta.mimeType()?.firstOrNull(),
+                mimeType = iMeta.mimeType()?.firstOrNull(),
-                iMeta.blurhash()?.firstOrNull(),
+                blurhash = iMeta.blurhash()?.firstOrNull(),
-                iMeta.dims()?.firstOrNull()?.let { DimensionTag.parse(it) },
+                dimension = iMeta.dims()?.firstOrNull()?.let { DimensionTag.parse(it) },
-                iMeta.alt()?.firstOrNull(),
+                alt = iMeta.alt()?.firstOrNull(),
-                iMeta.hash()?.firstOrNull(),
+                hash = iMeta.hash()?.firstOrNull(),
-                iMeta.size()?.firstOrNull()?.toIntOrNull(),
+                size = iMeta.size()?.firstOrNull()?.toIntOrNull(),
+                thumbhash = iMeta.thumbhash()?.firstOrNull(),
             )
     }
 }