Weird issue with weighting?

[Aerocatia]

When compressing this texture the cyan region encroaches into magenta. This happens even with color weights set to 1,1,1. This is compressing as DXT1A.

Here is with texpresso:

And here is with DirectXTex:

This is the input:

Should this be happening?

[Aerocatia]

I should mention that libsquish did not do this.

[jansol]

That should definitely not be happening, no. As a wild guess, could this be related to the image dimensions?

[Aerocatia]

Not sure, the image is 128x128. The split between the rows is exactly between a DXT block, so 2px each color.

[Kriskras99]

I can't seem to reproduce this. When running with texpresso compress -f BC1 input.png, I get Only images with 8 bits per channel are supported. When I convert the PNG with Gimp to 8bpc, I get the correct output with the above command.

[Aerocatia]

I'm still getting the issue and this is the code that does it https://github.com/Aerocatia/ringhopper-old/blob/30867cb07468e454d4ff49841f24d31630662e41/src/ringhopper/src/bitmap/compression/mod.rs#L264

However I can confirm building texpresso standalone works correctly...... EDIT: it breaks on standalone if you use --profile quality

[Kriskras99]

Can reproduce with --profile quality. I was hoping this bug was introduced at some point, but it's been here as long as there has been a CLI. It did flip at some point (magenta encroaching on cyan, instead of the reverse). Unfortunately I don't understand the algorithm well enough to figure out what is wrong.

[jansol]

Oh, it happening only with quality profile is a great hint! Quality is basically the same algorithm as balanced but it does multiple iterations of numerical refinement. So it seems something goes wrong after the 1st iteration...