Incorrect alpha channel when saving as BC7

[ghost]

Hi,

We have a problem when saving BC7 textures that have an alpha channel.

I've managed to create a very simple test case which demonstates the issue (although our actual usage is slightly different).

If an RGBA texture with all zero values in the alpha channel is saved as BC7, the resulting compressed texture may have non zero values in the alpha channel.

My simple test case is a 4x4 linear RGBA 2D texture with (111,111,111,0) in each texel.

When saved as BC7 the resulting texture will have (111,111,111,2) in each texel.

I have attached the texture.

thanks, Bill.

alpha_test_case.zip