BMP 24bit or 32bit(i.e. with alpha) source doesn't work

[nbonniere]

BMP source file format doesn't work, but after conversion of file from BMP to TGA, it works. BMP format is listed as supported, so why is it not supported ?

C:\Programs\Crunch2\bin>crunch -file 0101.bmp -fileformat dds -dxt3
crunch - Advanced DXTn Texture Compressor - https://github.com/FrozenStormInteractive/Crunch2

Copyright (c) 2010-2016 Richard Geldreich, Jr. and Binomial LLC
Copyright (c) 2020-2021 FrozenStorm Interactive, Yoann Potinet

crnlib version 1.2.0 x64 Built Jun 1 2021, 20:13:36

Reading source texture: "0101.bmp"
Error: Failed loading image file

Exit status: 1

C:\Programs\Crunch2\bin>crunch -file 0101.tga -fileformat dds -dxt3
crunch - Advanced DXTn Texture Compressor - https://github.com/FrozenStormInteractive/Crunch2

Copyright (c) 2010-2016 Richard Geldreich, Jr. and Binomial LLC
Copyright (c) 2020-2021 FrozenStorm Interactive, Yoann Potinet

crnlib version 1.2.0 x64 Built Jun 1 2021, 20:13:36

Reading source texture: "0101.tga"
Texture successfully loaded in 0.236s
Source texture: 4096x4096, Levels: 1, Faces: 1, Format: R8G8B8
Apparent type: 2D map, Flags: R G B Non-Flipped
Generating mipmaps using filter "kaiser"
Generated 12 mipmap levels in 3.310s
Converting texture format from R8G8B8 to DXT3
Processing: 100%
Texture format conversion took 12.150s
Writing texture to file: "0101.dds"

Texture successfully written in 12.185s
Texture successfully processed in 15.518s
Input texture: 4096x4096, Levels: 1, Faces: 1, Format: R8G8B8
Input pixels: 16777216, Input file size: 50331666, Input bits/pixel: 24.000
Output texture: 4096x4096, Levels: 13, Faces: 1, Format: DXT3
Output pixels: 22369621, Output file size: 22369776, Output bits/pixel: 8.000

Total time: 15.838s
1 total file(s) successfully processed, 0 file(s) skipped, 0 file(s) failed.

Exit status: 0

[nbonniere]

A test with the original 'crunch' and the same bitmap works OK.

C:\Programs\Crunch2\bin>crunch_x64.exe -DXT3 -fileformat dds -file 0101.bmp
crunch: Advanced DXTn Texture Compressor - http://code.google.com/p/crunch
Copyright (c) 2010-2012 Rich Geldreich and Tenacious Software LLC
crnlib version v1.04 x64 Built Nov 19 2015, 17:45:31

Reading source texture: "0101.bmp"
Texture successfully loaded in 0.308s
Source texture: 4096x4096, Levels: 1, Faces: 1, Format: A8R8G8B8
Apparent type: 2D map, Flags: R G B A Non-Flipped
Generating mipmaps using filter "kaiser"
Generated 12 mipmap levels in 3.442s
Converting texture format from A8R8G8B8 to DXT3
Processing: 100%
Texture format conversion took 14.131s
Writing texture to file: "0101.dds"

Texture successfully written in 14.171s
Texture successfully processed in 17.646s
Input texture: 4096x4096, Levels: 1, Faces: 1, Format: A8R8G8B8
Input pixels: 16777216, Input file size: 50331702, Input bits/pixel: 24.000
Output texture: 4096x4096, Levels: 13, Faces: 1, Format: DXT3
Output pixels: 22369621, Output file size: 22369776, Output bits/pixel: 8.000

Total time: 18.107s
1 total file(s) successfully processed, 0 file(s) skipped, 0 file(s) failed.

Exit status: 0