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Fix some webp images improperly marked as animated #29713

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Merged
merged 3 commits into from
Apr 11, 2025
Merged

Fix some webp images improperly marked as animated #29713

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c38ce86
Fix some webp images improperly marked as animated
Petersmit27 Apr 10, 2025
dbbbc06
Add unit test for an unanimated webp file in extended file format
Petersmit27 Apr 10, 2025
5174bba
Apply linting to webp test
Petersmit27 Apr 10, 2025
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4 changes: 2 additions & 2 deletions src/utils/Image.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -31,13 +31,13 @@ export async function blobIsAnimated(mimeType: string | undefined, blob: Blob):
case "image/webp": {
// Only extended file format WEBP images support animation, so grab the expected data range and verify header.
// Based on https://developers.google.com/speed/webp/docs/riff_container#extended_file_format
const arr = await blob.slice(0, 17).arrayBuffer();
const arr = await blob.slice(0, 21).arrayBuffer();
if (
arrayBufferReadStr(arr, 0, 4) === "RIFF" &&
arrayBufferReadStr(arr, 8, 4) === "WEBP" &&
arrayBufferReadStr(arr, 12, 4) === "VP8X"
) {
const [flags] = arrayBufferRead(arr, 16, 1);
const [flags] = arrayBufferRead(arr, 20, 1);
// Flags: R R I L E X _A_ R (reversed)
const animationFlagMask = 1 << 1;
return (flags & animationFlagMask) != 0;
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5 changes: 5 additions & 0 deletions test/unit-tests/Image-test.ts
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Expand Up @@ -51,6 +51,11 @@ describe("Image", () => {
expect(await blobIsAnimated("image/webp", img)).toBeFalsy();
});

it("Static WEBP in extended file format", async () => {
const img = new Blob([fs.readFileSync(path.resolve(__dirname, "images", "static-logo-extended-file-format.webp"))]);
expect(await blobIsAnimated("image/webp", img)).toBeFalsy();
});

it("Animated PNG", async () => {
const img = new Blob([fs.readFileSync(path.resolve(__dirname, "images", "animated-logo.apng"))]);
expect(await blobIsAnimated("image/png", img)).toBeTruthy();
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Binary file added test/unit-tests/images/static-logo-extended-file-format.webp
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Well that got a good laugh from me

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