Image masks not working properly

[Danar435]

This issue might be very specific and a little hard to explain. In Little Busters, near the end of Kud's route, you have this white screen which slowly morphs into a CG. It's done via one of 4 masks found at the bottom of OTHCG.PAK. It is a CZ0 image using an 8-bit color space, where the color palette follows a specific pattern, starting from black and slowly turning white.

000000FF, 010101FF ... FEFEFEFF, FFFFFFFF

I assume that the engine follows the chronological order of the palette and slowly decreases each color's transparency to reveal the CG underneath the white screen. Using czutil creates a palette that's all over the place, and this is what happens:

Screencast_From_2025-09-07_19-21-49.mp4

I did manage to fix it by manually converting the image and copying the header data over to it, but of course it would be nice if czutil could also do it. I'm not sure if these masks are used in any other games though. Here is how the mask looks like and the original cz files:

https://cloud.kristiyan.cc/api/public/dl/7tW45FNM/Shared/NYKD_MASK01-unpacked
https://cloud.kristiyan.cc/api/public/dl/xEqcYFiW/Shared/NYKD_MASK01-repacked

[G2-Games]

So is the issue that the palette is incorrect? Is the behavior in the video the incorrect one?

I guess my palette reconstruction that I thought would do no harm might be messing it up. I think I can add a flag to disable that forcefully if needed.

[G2-Games]

The latest release should fix this issue if you use the --no-clear-palette option, but keep in mind while this can be used in batch mode, I would not recommend it.