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Replace the EXIF-block with dummy data to prevent JPEG images being rotated (bug 1942064)

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The `ImageDecoder` will respect the EXIF orientation, which can lead to JPEG images being incorrectly rotated. To avoid this we replace the entire EXIF-block with dummy data, which works since it'll cause EXIF parsing to bail out early in Firefox; see https://searchfox.org/mozilla-central/rev/9a66d18cb35595c89f499a1011c9dd7e573fce77/image/decoders/EXIF.cpp#130-138
This commit is contained in:
Jonas Jenwald 2025-01-19 10:49:47 +01:00
parent 01d542eee5
commit c4ba3ac23f
4 changed files with 31 additions and 0 deletions
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23
src/core/jpg.js
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@ -817,6 +817,29 @@ class JpegImage {
markerLoop: while (fileMarker !== /* EOI (End of Image) = */ 0xffd9) {
switch (fileMarker) {
case 0xffe1: // APP1 - Exif
// TODO: Remove this once https://github.com/w3c/webcodecs/issues/870
// is fixed.
const { appData, newOffset } = readDataBlock(data, offset);
offset = newOffset;
// 'Exif\x00\x00'
if (
appData[0] === 0x45 &&
appData[1] === 0x78 &&
appData[2] === 0x69 &&
appData[3] === 0x66 &&
appData[4] === 0 &&
appData[5] === 0
) {
// Replace the entire EXIF-block with dummy data, to ensure that a
// non-default EXIF orientation won't cause the image to be rotated
// when using `ImageDecoder` (fixes bug1942064.pdf).
appData.fill(0x00, 6);
}
fileMarker = readUint16(data, offset);
offset += 2;
continue;
case 0xffc0: // SOF0 (Start of Frame, Baseline DCT)
case 0xffc1: // SOF1 (Start of Frame, Extended DCT)
case 0xffc2: // SOF2 (Start of Frame, Progressive DCT)