Rock Band 2 Wii texture transparency bugs (decoding and encoding)

[LlysiX]

When converting png_wii/tex files from Rock Band 2 that have transparency, the alpha channel is lost. Converting these textures back causes a black square to be shown around the texture. tex2png output: repacked in game representation: expected:

When the texture is read/extracted using Dolphin's texture dumper, it is output as 2 separate textures, one matching the tex2png output and another white one (possibly the missing alpha channel?):

Converting pngs with transparency to png_wii causes this to happen when loaded in game: source png:

[PikminGuts92]

What's the name and location of texture in the game?

[PikminGuts92]

I'm gonna assume it's track\textures\gen\rb2_player_meter_background.bmp_wii. I looked at it and it appears there's a hidden alpha data after mip data. Interestingly, it's only for largest mip image. This seems to be indicated by a set of bytes after bytes per line in bitmap header.

https://github.com/PikminGuts92/re-notes/blob/476a86f963e839b898d7814f8d535f37e49c208b/templates/milo/bitmap.bt#L152 https://github.com/PikminGuts92/re-notes/blob/476a86f963e839b898d7814f8d535f37e49c208b/templates/milo/bitmap.bt#L201-L205

RGB image

Alpha image

Combined image

I updated dev branch to properly read in this alpha data. Please test it out and see if that works for you. Note that converting png to png_wii will still use 8bpp encoding instead of this strange alternative.

GitHub Actions Download: https://github.com/PikminGuts92/Mackiloha/actions/runs/8166985000

[LlysiX]

Sorry for not responding, yes track\textures\gen\rb2_player_meter_background.bmp_wii is the file.

I can confirm that all textures that had a missing alpha channel previously now have their alphas intact with this new build.