DNG files from Canon 550D show strong purple color cast

[odeemi]

First off, thank you for creating RapidRAW - it looks like an excellent project!

I'm experiencing a color rendering issue with some of my older DNG files and wanted to report it:

Problem:
When opening DNG files in RapidRAW (macOS binary), the images display with a strong purple/magenta color cast. These are DNG files that were originally shot on a Canon 550D and converted to DNG format back in the day (likely with Lightroom on Windows).

Files work correctly in:

• macOS Preview
• Affinity Photo

Environment:

• Platform: macOS
• RapidRAW version: 1.3.9
• File format: DNG (converted from Canon 550D CR2 files when imported with Ligtroom in Windows)

Example image:

[CyberTimon]

This is dnglab / rawler-related, so it’s not entirely in my hands whether the underlying RAW loader supports it. I’ll try to patch it in the future to make it work.

[odeemi]

I read a little bit on this and to my understanding the purple cast occurs because dnglab/rawler incorrectly prioritizes ColorMatrix over ForwardMatrix when both are present in DNG files, and applies white balance multipliers in the wrong sequence. Adobe DNG Converter often embeds desaturated ForwardMatrix values designed to work with LUTs that dnglab doesn't implement, causing the color shift.

I think this issue is with all Canon 18MP APS-C sensors.

Example files (dng and xmp) here: https://drive.google.com/drive/folders/1QDFujC235T3tHjWgxvURT1AnLVZMhVSl?usp=share_link