[BUG] CMYK jpg to regular jpg is broken

[joshyoo-topazlabs]

Describe the bug

cmyk_to_rgb() seems to be broken in the 3.1.6.0 and 3.1.7.0 versions(possibly others as well). I noticed when using openimageio within a project, and I was able to reproduce the issue using oiiotool. This does NOT happen with an older versions such as 3.0.10.1. I was able to verify that this happens when building from source, and on both windows and mac.

I am specifically testing by importing a cmyk jpg image, and outputting a regular jpg.

OpenImageIO version and dependencies

OIIO 3.1.6.2 | MacOS/ARM Build compiler: Apple clang 17.0 | C++17/201703 HW features enabled at build: neon No CUDA support (disabled / unavailable at build time) Dependencies: BZip2 1.0.8, DCMTK NONE, expat 2.6.4, FFmpeg NONE, fmt 10.2.1, Freetype 2.13.3, GIF NONE, Imath 3.1.12, JXL NONE, Libheif 1.19.8, libjpeg-turbo 3.1.0, LibRaw 0.21.3, libuhdr 1.4.0, minizip-ng 4.0.7, OpenColorIO 2.4.2, OpenCV NONE, OpenEXR 3.2.4, OpenGL, OpenJPEG 2.5.3, openjph 0.23.1, PNG 1.6.47, Ptex NONE, Ptex NONE, pybind11 3.0.1, pystring, Python3 3.13.3, Qt5 NONE, Qt6 NONE, Robinmap 1.4.0, TBB NONE, TIFF 4.7.0, WebP 1.6.0, yaml-cpp 0.8.0, ZLIB 1.3.1, ZLIB 1.3.1

To Reproduce

1. run make

2. use oiiotool to import a cmyk .jpg image then output a .jpg
   ./oiiotool ./CMYK.jpg --resize 640x420 -o ./cmyk-to-rgb-jpg.jpg

Evidence

-- Error message
[1] 25028 bus error ./oiiotool --resize 640x420 -o

-- Debug
Process 25077 launched: '.../OpenImageIO/build/bin/oiiotool' (arm64) Process 25077 stopped thread #11, stop reason = EXC_BAD_ACCESS (code=2, address=0x170378000) frame #0: 0x00000001014f2484 libOpenImageIO.3.1.dylibOpenImageIO::v3_1::cmyk_to_rgb(int, unsigned char const*, unsigned long, unsigned char*, unsigned long) + 880
libOpenImageIO.3.1.dylibOpenImageIO::v3_1::cmyk_to_rgb: -> 0x1014f2484 <+880>: ld4.16b { v17, v18, v19, v20 }, [x14], #64 0x1014f2488 <+884>: tbl.16b v21, { v17 }, v0 0x1014f248c <+888>: tbl.16b v22, { v17 }, v1 0x1014f2490 <+892>: tbl.16b v23, { v17 }, v3

Sample Data

[lgritz]

You are quite right, there was a bug. Proposed solution in #4963.

I was able to test on your image, but it's too big (and I'm not sure of the licensing) to add to our testsuite. Is it possible that you can supply a small JPEG test image in CMYK that we can use as a test?

[joshyoo-topazlabs]

Thanks for getting back so quick! I'm sorry but thats the smallest one that I have :(
Do you think this will be merged soon?

[lgritz]

It just needs somebody to review the code, or for me to get frustrated enough to merge without review. Either way, I will merge it in time for the 3.0 and 3.1 patch releases scheduled for Dec 1.

I would love to add a small test image, but I don't have a way to generate an jpeg image in that cmyk mode. (OIIO can read them, but can't write them.) Like a tiny 16x16 image is fine, I want it as small as possible, just enough to verify that this feature keeps working. I don't want to add 3MB to the project download to test this one extremely rarely used feature.

Aha, wait, I think I found a way to do it. Stay tuned, I will amend the PR with a test.