32-bit BMPs support an alpha channel. I've attached one I exported with pre-multiplied alpha from Pixel Former
SkeletonAttack.zip
Ideally it would be using pre-multiplied alpha as in PixelFormer but I'd be happy with even just the alpha channel - here's a video of how it works in PS
https://www.youtube.com/watch?v=3LJCss690vs
These bitmaps can be loaded and displayed with transparency in SDL2 without any additonal libs.
32-bit BMPs support an alpha channel. I've attached one I exported with pre-multiplied alpha from Pixel Former SkeletonAttack.zip
Ideally it would be using pre-multiplied alpha as in PixelFormer but I'd be happy with even just the alpha channel - here's a video of how it works in PS https://www.youtube.com/watch?v=3LJCss690vs
These bitmaps can be loaded and displayed with transparency in SDL2 without any additonal libs.
Aseprite and System version