Article only mentions manually building an irregularly shaped region from an image

> Every horizontal run of non-transparent pixels becomes a tiny rectangle region, and those runs are combined into one final window region

but there's an easier way: you just use a LWA_COLORKEY with SetLayeredWindowAttributes to make a color transparent, like a green screen. I recall building my own desktop mascot that way. Doesn't work with arbitrary image/content of course since the color can't appear in the content region.