Fix JPEG segment ordering per JFIF and CIPA DC-007 standards#394
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minatoAI wants to merge 1 commit into
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Fix JPEG segment ordering per JFIF and CIPA DC-007 standards#394minatoAI wants to merge 1 commit into
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The appendGainMap function built JPEG output with incorrect marker ordering: - JFIF (APP0) was written after XMP, ISO, MPF and ICC segments (must be the first APP marker after SOI per JFIF spec) - MPF was written before JFIF and ICC, far from SOS (must be placed right before SOS per CIPA DC-007) This caused platforms like Xiaohongshu to fail HDR recognition because their decoders follow the standard marker ordering. Fix: 1. Extract APP0(JFIF) from the base JPEG data and write it right after SOI 2. Parse the base JPEG marker segments (DQT, SOF, DHT) and write them before MPF 3. Write MPF right before SOS per CIPA DC-007 4. Write SOS + compressed data after MPF Also: - Added rdf:about="" attribute and hdrgm:OplusScale field to the gain map XMP metadata block (required by Android Ultra HDR specification) - Added -DWITH_CRT_DLL=ON to turbojpeg ExternalProject for MSVC compatibility - When BUILD_FOR_WINUI is defined, skip the forced /MT CRT override
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Summary
The
appendGainMapfunction builds JPEG output with incorrect APP marker ordering:This causes HDR decoders that follow the standard ordering (e.g., Xiaohongshu/小红书) to fail to recognize the Ultra HDR gain map.
Changes
lib/src/jpegr.cpp: Extract APP0(JFIF) from the base JPEG data and write it immediately after SOI. Parse the base JPEG marker segments (DQT, SOF, DHT) and write them before MPF. Write MPF right before SOS per CIPA DC-007.
lib/src/jpegrutils.cpp: Add
rdf:about=""attribute andhdrgm:OplusScale="-1"field to the gain map XMP metadata block, matching the Android Ultra HDR specification (developer.android.com/media/platform/hdr-image-format).CMakeLists.txt: Add
-DWITH_CRT_DLL=ONto turbojpeg's ExternalProject CMAKE_ARGS when building on MSVC, to prevent CRT mismatch when the parent project uses dynamic CRT (/MD).Testing
Verified that the fix produces a JPEG segment order identical to camera-captured Ultra HDR images (e.g., OPPO Find X8 Ultra), and the reordered file is correctly recognized as HDR by the Xiaohongshu platform.