From d1926fb1791150640d818cb09819f4fe6a60c205 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Wed, 10 Jun 2026 18:27:50 +0200
Subject: [PATCH] Use the `convertBlackAndWhiteToRGBA` helper with grayscale
 images in `putBinaryImageData`

This removes a little bit of code duplication, which only exist since the `src/display/canvas.js` code pre-dates the helper function by many years.

*Note:* Given that `OffscreenCanvas` is enabled by default there's currently not a lot of test coverage for this code-path, hence the added browser-test.
---
 src/display/canvas.js   | 46 +++++++----------------------------------
 test/test_manifest.json |  8 +++++++
 2 files changed, 15 insertions(+), 39 deletions(-)

diff --git a/src/display/canvas.js b/src/display/canvas.js
index 9e7ddd334..8561a4939 100644
--- a/src/display/canvas.js
+++ b/src/display/canvas.js
@@ -349,48 +349,16 @@ function putBinaryImageData(ctx, imgData) {
   // imgData.kind tells us which one this is.
   if (imgData.kind === ImageKind.GRAYSCALE_1BPP) {
     // Grayscale, 1 bit per pixel (i.e. black-and-white).
-    const srcLength = src.byteLength;
-    const dest32 = new Uint32Array(dest.buffer, 0, dest.byteLength >> 2);
-    const dest32DataLength = dest32.length;
-    const fullSrcDiff = (width + 7) >> 3;
-    const white = 0xffffffff;
-    const black = FeatureTest.isLittleEndian ? 0xff000000 : 0x000000ff;
-
     for (i = 0; i < totalChunks; i++) {
       thisChunkHeight = i < fullChunks ? FULL_CHUNK_HEIGHT : partialChunkHeight;
-      destPos = 0;
-      for (j = 0; j < thisChunkHeight; j++) {
-        const srcDiff = srcLength - srcPos;
-        let k = 0;
-        const kEnd = srcDiff > fullSrcDiff ? width : srcDiff * 8 - 7;
-        const kEndUnrolled = kEnd & ~7;
-        let mask = 0;
-        let srcByte = 0;
-        for (; k < kEndUnrolled; k += 8) {
-          srcByte = src[srcPos++];
-          dest32[destPos++] = srcByte & 128 ? white : black;
-          dest32[destPos++] = srcByte & 64 ? white : black;
-          dest32[destPos++] = srcByte & 32 ? white : black;
-          dest32[destPos++] = srcByte & 16 ? white : black;
-          dest32[destPos++] = srcByte & 8 ? white : black;
-          dest32[destPos++] = srcByte & 4 ? white : black;
-          dest32[destPos++] = srcByte & 2 ? white : black;
-          dest32[destPos++] = srcByte & 1 ? white : black;
-        }
-        for (; k < kEnd; k++) {
-          if (mask === 0) {
-            srcByte = src[srcPos++];
-            mask = 128;
-          }
 
-          dest32[destPos++] = srcByte & mask ? white : black;
-          mask >>= 1;
-        }
-      }
-      // We ran out of input. Make all remaining pixels transparent.
-      while (destPos < dest32DataLength) {
-        dest32[destPos++] = 0;
-      }
+      ({ srcPos } = convertBlackAndWhiteToRGBA({
+        src,
+        srcPos,
+        dest,
+        width,
+        height: thisChunkHeight,
+      }));
 
       ctx.putImageData(chunkImgData, 0, i * FULL_CHUNK_HEIGHT);
     }
diff --git a/test/test_manifest.json b/test/test_manifest.json
index f44db6344..aef2038d3 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -5389,6 +5389,14 @@
     "rounds": 1,
     "type": "eq"
   },
+  {
+    "id": "images_1bit_grayscale-disable-isOffscreenCanvasSupported",
+    "file": "pdfs/images_1bit_grayscale.pdf",
+    "md5": "e1c36a19563944891bd30cfc0199d07f",
+    "rounds": 1,
+    "type": "eq",
+    "isOffscreenCanvasSupported": false
+  },
   {
     "id": "html5checker",
     "file": "pdfs/html5checker.pdf",