[Bug 47018] Multiple applications show transparent bitmap images on static controls with black background (comctl32 lacking support for painting 32-bit BMPv3 with alpha channel)

https://bugs.winehq.org/show_bug.cgi?id=47018

--- Comment #30 from Olivier F. R. Dierick  ---
(In reply to double55 from comment #29)
> This fix transparent alpha channel or only >0?

Hello,

The patch makes Wine calls GdiAlphaBlend() when at least one pixel has a
non-zero alpha channel. If all pixel have alpha channel 0, then the image is
considered opaque (this will be wrong for full transparent images, but who
would use a full transparent image, anyway?).

The blending function uses the full alpha channel range (0-255).

If you see artifacts in the transparent image, that is another issue. (My tests
show that the current Wine alpha blending function doesn't give a smooth alpha
result).

Regards