BC4 compression with R8 input results in a black texture

[tiiago11]

Hello,

After updating the library to v3.2.4691, it seems the BC4/ATI1N compression is producing a black texture when provided a R8 texture as input. This can be reproduced in the GUI and also with the SDK API.

As far as I could trace, the bufferIn.m_bSwizzle flag is wrongly set to true for this input format, which results in in the CCodecBuffer_R8::ReadBlockB getting called, which returns always 0 for this channel. The commit that introduced this verification of this flag in the CCodec_ATI1N::Compress_Fast codec is:
92f888f#diff-fc1b13a6a8de118ff844e5041f950301L121
A workaround I managed to do is to add CBT_R8 to the switch here:

compressonator/Compressonator/CMP_CompressonatorLib/Compress.cpp

Line 542 in 7d56f15

case CBT_BGR888:

Is this is a known issue? is there another fix/workaround that can be done from outside the library?

Thank you for the support!

[NPCompress]

@tiiago11 "Is this is a known issue? " No, its the first time been reported. The patch you used is applied to the release that is scheduled for next week.

"is there another fix/workaround that can be done from outside the library?" You can use the low -level BC4 block encoder available in CMP_Core.