Describe the bug
When converting a particular JXL image to PNG, the PNG has noticeable color issues with patches of discoloration.

To Reproduce
Download this

djxl theimage.jxl out.png

Compare the png to the JXL.

Expected behavior
The PNG would be visually identical to the JXL, or at least close enough where I wouldn't see obvious discoloration or where the PNG is earning horrible ssimu2 scores.

Screenshots
If applicable, add screenshots or example input/output images to help explain your problem.

Environment

• OS: Linux
• Compiler version: gcc (GCC) 12.2.1 20230201
• CPU type: x86_64
• cjxl/djxl version string: djxl v0.9.0 13caf6f [AVX2,SSE4,SSSE3,SSE2]

Additional context
The problem persists with other versions of cjxl/djxl when using the source PNG (which is almost 100mb).