Save result to BMP file with 24 bits

[Dawnlnz]

When I save the result to BMP, I need to do alpha blending with black BG. If not , there's a lot of serrations in the BMP. Why?

[oehhar]

I can only say, that a full alpha channel is supported. BMP has internally lots of formats and not all formats support a full alpha channel. Most bmp formats only support a one bit alpha channel. Wouldn't it preferable to save the image in png which always features a full alpha channel?