PNG cICP data not handled

[skidder]

Problem Summary

Discord's image processing pipeline currently doesn't properly handle PNG images that contain cICP (Color Information Chunk for PNG) data. This specifically affects HDR PNG images, which include color space and transfer characteristics information in the cICP chunk as defined in the PNG 3 specification. When these images are uploaded to Discord, the application ignores this color profile information, resulting in significant color/hue shifts.

Technical Details

• The issue specifically relates to Discord not handling PQ (Perceptual Quantizer) transfer characteristics in PNG source files
• The PNG file format specification (W3C CR-png-3-20250313) includes a cICP chunk that contains critical color space information
• This problem is similar to that corrected in fix: Prefer cicp metadata from AVIF sources. #243

Impact

Users are experiencing major hue shifts in images, likely due to mismatched color primaries. This is particularly noticeable with HDR content that's being incorrectly converted to SDR (Standard Dynamic Range).

Affected Content

While HDR PNGs are described as "uncommon," they can be generated by devices like the PlayStation 5. The issue has been confirmed with specific PNG examples shared by users.