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| author | Elliott Hughes <enh@google.com> | 2020-12-02 18:09:57 -0800 |
|---|---|---|
| committer | Elliott Hughes <enh@google.com> | 2020-12-02 18:24:38 -0800 |
| commit | 98e581f8227b9846b7adc92c0c63f5ed2384ff4b (patch) | |
| tree | 26effec72dbace7671158aeddc9fde1e3e9cd1a9 /README.android | |
| parent | ff78ee5a324a7d37e0bfffd6152ea37056f29931 (diff) | |
| parent | d5148db386ceb4a608058320071cbed890bd6ad2 (diff) | |
Switch to chromium upstream.
Bug: https://issuetracker.google.com/135180511
Test: treehugger
Change-Id: I0c78ec9b07debdb501a96df0d6cb2f9a24b5fc84
Diffstat (limited to 'README.android')
| -rw-r--r-- | README.android | 35 |
1 files changed, 15 insertions, 20 deletions
diff --git a/README.android b/README.android index 12f476d..b2003e8 100644 --- a/README.android +++ b/README.android @@ -1,20 +1,15 @@ -Any Android specific modifications to upstream libjpeg-turbo (the version -specified in METADATA) should be listed here: - -(1) jconfig.h and jconfigint.h - -These are included upstream as jconfig.h.in and jconfigint.h.in. -We have the option autogenerate these platform/version specific files (using -the libjpeg-turbo build system) or to manually create them. - -Autogenerating these files on linux gets us most of the way, but we've needed -to add some multi-platform flexibility to the INLINE and SIZEOF_SIZE_T macros. - -(2) simd/arm64/jsimd_neon.S - -To support execute-only memory layouts, constants in handwritten assembly have -been moved into a dedicated rodata section. - -There's a pull request upstream for this as well. If that's accepted, this -can be removed as an Android-specific modification. -https://github.com/libjpeg-turbo/libjpeg-turbo/pull/318 +# Android differences from upstream chromium + +Android builds with `C_ARITH_CODING_SUPPORTED` and `D_ARITH_CODING_SUPPORTED`, +added in +https://android-review.googlesource.com/c/platform/external/libjpeg-turbo/+/291407/ +to support a variant of jpeg files using arithmetic (instead of Huffman) +encoding. This variant isn't often used because of a lack of support in many +viewers (e.g. Chromium), but Android really values backwards compatibility, and +this might break some users. Android probably only needs to keep +`D_ARITH_CODING_SUPPORTED`, but vendor code might also be encoding by setting +jpeg_compress_struct.arith_code to true, so we enable both to ensure full +backwards compatibility since it's not really costing us anything. +We `#define` these in jconfig.h rather than in Android.bp so that they're +correctly exported to any *users* (in particular, jerror.h only conditionally +defines the corresponding error codes if these `#define`s are present). |