From 3d8df74b4327f6cd6571f91046eacdfa04428bb9 Mon Sep 17 00:00:00 2001
From: Min Idzelis <min123@gmail.com>
Date: Wed, 15 Apr 2026 21:18:49 -0400
Subject: [PATCH] refactor(web): turn thumbhash action into Thumbhash component
 (#27741)

refactor(web): extract thumbhash canvas into Thumbhash component

Change-Id: If78955bed48b6e690df398e5e2ae61fb6a6a6964
---
 web/src/lib/actions/thumbhash.ts              | 29 --------------
 web/src/lib/components/AdaptiveImage.svelte   |  4 +-
 web/src/lib/components/Thumbhash.svelte       | 40 +++++++++++++++++++
 .../asset-viewer/photo-viewer.svelte          |  7 +---
 .../assets/thumbnail/thumbnail.svelte         | 21 ++++------
 5 files changed, 51 insertions(+), 50 deletions(-)
 delete mode 100644 web/src/lib/actions/thumbhash.ts
 create mode 100644 web/src/lib/components/Thumbhash.svelte

diff --git a/web/src/lib/actions/thumbhash.ts b/web/src/lib/actions/thumbhash.ts
deleted file mode 100644
index 872d3d03bf..0000000000
--- a/web/src/lib/actions/thumbhash.ts
+++ /dev/null
@@ -1,29 +0,0 @@
-import { decodeBase64 } from '$lib/utils';
-import { thumbHashToRGBA } from 'thumbhash';
-
-/**
- * Renders a thumbnail onto a canvas from a base64 encoded hash.
- */
-export function thumbhash(canvas: HTMLCanvasElement, options: { base64ThumbHash: string }) {
-  render(canvas, options);
-
-  return {
-    update(newOptions: { base64ThumbHash: string }) {
-      render(canvas, newOptions);
-    },
-  };
-}
-
-const render = (canvas: HTMLCanvasElement, options: { base64ThumbHash: string }) => {
-  const ctx = canvas.getContext('2d');
-  if (!ctx) {
-    return;
-  }
-
-  const { w, h, rgba } = thumbHashToRGBA(decodeBase64(options.base64ThumbHash));
-  const pixels = ctx.createImageData(w, h);
-  canvas.width = w;
-  canvas.height = h;
-  pixels.data.set(rgba);
-  ctx.putImageData(pixels, 0, 0);
-};
diff --git a/web/src/lib/components/AdaptiveImage.svelte b/web/src/lib/components/AdaptiveImage.svelte
index f60260bd05..ed574cbe39 100644
--- a/web/src/lib/components/AdaptiveImage.svelte
+++ b/web/src/lib/components/AdaptiveImage.svelte
@@ -1,9 +1,9 @@
 <script lang="ts">
-  import { thumbhash } from '$lib/actions/thumbhash';
   import AlphaBackground from '$lib/components/AlphaBackground.svelte';
   import BrokenAsset from '$lib/components/assets/broken-asset.svelte';
   import DelayedLoadingSpinner from '$lib/components/DelayedLoadingSpinner.svelte';
   import ImageLayer from '$lib/components/ImageLayer.svelte';
+  import Thumbhash from '$lib/components/Thumbhash.svelte';
   import { assetViewerManager } from '$lib/managers/asset-viewer-manager.svelte';
   import { getAssetUrls } from '$lib/utils';
   import { AdaptiveImageLoader, type QualityList } from '$lib/utils/adaptive-image-loader.svelte';
@@ -165,7 +165,7 @@
     {#if show.thumbhash}
       {#if asset.thumbhash}
         <!-- Thumbhash / spinner layer  -->
-        <canvas use:thumbhash={{ base64ThumbHash: asset.thumbhash }} class="h-full w-full absolute"></canvas>
+        <Thumbhash base64ThumbHash={asset.thumbhash} class="h-full w-full absolute" />
       {:else if show.spinner}
         <DelayedLoadingSpinner />
       {/if}
diff --git a/web/src/lib/components/Thumbhash.svelte b/web/src/lib/components/Thumbhash.svelte
new file mode 100644
index 0000000000..5cda4ad53a
--- /dev/null
+++ b/web/src/lib/components/Thumbhash.svelte
@@ -0,0 +1,40 @@
+<script lang="ts">
+  import { decodeBase64 } from '$lib/utils';
+  import { TUNABLES } from '$lib/utils/tunables';
+  import type { HTMLCanvasAttributes } from 'svelte/elements';
+  import { fade } from 'svelte/transition';
+  import { thumbHashToRGBA } from 'thumbhash';
+
+  type Props = HTMLCanvasAttributes & {
+    base64ThumbHash: string;
+    fadeOut?: boolean;
+  };
+
+  const { base64ThumbHash, fadeOut = false, class: className, ...restProps }: Props = $props();
+
+  const {
+    IMAGE_THUMBNAIL: { THUMBHASH_FADE_DURATION },
+  } = TUNABLES;
+
+  let canvas = $state<HTMLCanvasElement>();
+
+  $effect(() => {
+    const ctx = canvas?.getContext('2d');
+    if (!canvas || !ctx) {
+      return;
+    }
+    const { w, h, rgba } = thumbHashToRGBA(decodeBase64(base64ThumbHash));
+    canvas.width = w;
+    canvas.height = h;
+    const pixels = ctx.createImageData(w, h);
+    pixels.data.set(rgba);
+    ctx.putImageData(pixels, 0, 0);
+  });
+</script>
+
+<canvas
+  bind:this={canvas}
+  class={className}
+  out:fade={{ duration: fadeOut ? THUMBHASH_FADE_DURATION : 0 }}
+  {...restProps}
+></canvas>
diff --git a/web/src/lib/components/asset-viewer/photo-viewer.svelte b/web/src/lib/components/asset-viewer/photo-viewer.svelte
index a3c560ef8d..da00980f08 100644
--- a/web/src/lib/components/asset-viewer/photo-viewer.svelte
+++ b/web/src/lib/components/asset-viewer/photo-viewer.svelte
@@ -1,9 +1,9 @@
 <script lang="ts">
   import { shortcuts } from '$lib/actions/shortcut';
-  import { thumbhash } from '$lib/actions/thumbhash';
   import { zoomImageAction } from '$lib/actions/zoom-image';
   import AdaptiveImage from '$lib/components/AdaptiveImage.svelte';
   import FaceEditor from '$lib/components/asset-viewer/face-editor/face-editor.svelte';
+  import Thumbhash from '$lib/components/Thumbhash.svelte';
   import OcrBoundingBox from '$lib/components/asset-viewer/ocr-bounding-box.svelte';
   import AssetViewerEvents from '$lib/components/AssetViewerEvents.svelte';
   import { assetViewerManager } from '$lib/managers/asset-viewer-manager.svelte';
@@ -242,10 +242,7 @@
   >
     {#snippet backdrop()}
       {#if blurredSlideshow}
-        <canvas
-          use:thumbhash={{ base64ThumbHash: asset.thumbhash! }}
-          class="absolute top-0 left-0 inset-s-0 h-dvh w-dvw"
-        ></canvas>
+        <Thumbhash base64ThumbHash={asset.thumbhash!} class="absolute top-0 left-0 inset-s-0 h-dvh w-dvw" />
       {/if}
     {/snippet}
     {#snippet overlays()}
diff --git a/web/src/lib/components/assets/thumbnail/thumbnail.svelte b/web/src/lib/components/assets/thumbnail/thumbnail.svelte
index 3413e912b0..7aaa46107d 100644
--- a/web/src/lib/components/assets/thumbnail/thumbnail.svelte
+++ b/web/src/lib/components/assets/thumbnail/thumbnail.svelte
@@ -1,5 +1,4 @@
 <script lang="ts">
-  import { thumbhash } from '$lib/actions/thumbhash';
   import { ProjectionType } from '$lib/constants';
   import { authManager } from '$lib/managers/auth-manager.svelte';
   import type { TimelineAsset } from '$lib/managers/timeline-manager/types';
@@ -10,7 +9,6 @@
   import { moveFocus } from '$lib/utils/focus-util';
   import { currentUrlReplaceAssetId } from '$lib/utils/navigation';
   import { getAltText } from '$lib/utils/thumbnail-util';
-  import { TUNABLES } from '$lib/utils/tunables';
   import { AssetMediaSize, AssetVisibility, type UserResponseDto } from '@immich/sdk';
   import { Icon } from '@immich/ui';
   import {
@@ -27,6 +25,7 @@
   import { onMount } from 'svelte';
   import type { ClassValue } from 'svelte/elements';
   import { fade } from 'svelte/transition';
+  import Thumbhash from '$lib/components/Thumbhash.svelte';
   import ImageThumbnail from './image-thumbnail.svelte';
   import VideoThumbnail from './video-thumbnail.svelte';
   interface Props {
@@ -75,10 +74,6 @@
     dimmed = false,
   }: Props = $props();
 
-  let {
-    IMAGE_THUMBNAIL: { THUMBHASH_FADE_DURATION },
-  } = TUNABLES;
-
   let usingMobileDevice = $derived(mediaQueryManager.pointerCoarse);
   let element: HTMLElement | undefined = $state();
   let mouseOver = $state(false);
@@ -312,16 +307,14 @@
       {/if}
 
       {#if (!loaded || thumbError) && asset.thumbhash}
-        <canvas
-          use:thumbhash={{ base64ThumbHash: asset.thumbhash }}
+        <Thumbhash
+          base64ThumbHash={asset.thumbhash}
           data-testid="thumbhash"
-          class="absolute top-0 object-cover group-focus-visible:rounded-lg"
-          style:width="{width}px"
-          style:height="{height}px"
-          class:rounded-xl={selected}
+          class={['absolute top-0 object-cover group-focus-visible:rounded-lg', { 'rounded-xl': selected }]}
+          style="width: {width}px; height: {height}px"
           draggable="false"
-          out:fade={{ duration: THUMBHASH_FADE_DURATION }}
-        ></canvas>
+          fadeOut
+        />
       {/if}
 
       <!-- icon overlay -->