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JpegEmbedder: Support Buffers that have data in their backing buffer is offset #1273

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JpegEmbedder: Support Buffers that have data in their backing buffer is offset #1273

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6 changes: 5 additions & 1 deletion src/core/embedders/JpegEmbedder.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,11 @@ const ChannelToColorSpace: { [idx: number]: ColorSpace | undefined } = {
*/
class JpegEmbedder {
static async for(imageData: Uint8Array) {
const dataView = new DataView(imageData.buffer);
const dataView = new DataView(
imageData.buffer,
imageData.byteOffset,
imageData.byteLength,
);

const soi = dataView.getUint16(0);
if (soi !== 0xffd8) throw new Error('SOI not found in JPEG');
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13 changes: 13 additions & 0 deletions tests/core/embedders/JpegEmbedder.spec.ts
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Expand Up @@ -59,4 +59,17 @@ describe(`JpegEmbedder`, () => {
expect(embedder.width).toBe(500);
expect(embedder.colorSpace).toBe('DeviceCMYK');
});

it(`can extract properties of JPEG images have offset backing buffers`, async () => {
// This can happen with buffers that are pooled or sprite sheets
const oddCmykJpg = Buffer.alloc(10 + cmykJpg.byteLength);
cmykJpg.copy(oddCmykJpg, 10);
const oddCmykJpgView = oddCmykJpg.subarray(10);
const embedder = await JpegEmbedder.for(oddCmykJpgView);

expect(embedder.bitsPerComponent).toBe(8);
expect(embedder.height).toBe(333);
expect(embedder.width).toBe(500);
expect(embedder.colorSpace).toBe('DeviceCMYK');
});
});