Hi all. New user here, learning the ropes as I go along.
I found myself having a similar need as the OP: I have a .bmp with a bunch of images against a fuchsia background, and I need to replace the fuchsia with transparency to produce a PNG file.
I've been looking and searching over the past few days and finally got to BGRABitmap, but now I'm stuck with the issue of black getting replaced by a weird clear color. Unfortunately the last suggestion by circular -replacing black with blackopaque- didn't work. Moreover, all my attempts to replace black with ANY color using ReplaceColor were fruitless.
But then I saved as a .bmp and it looked correct, only with no transparency. So I think I managed to narrow the problem - it happens when saving to a filename with the extension '.png'. So my guess is the issue may lie within the call to "savetofile"? That's as far as I got based on my current skill level. I'd like to keep using BGRABitmap as it seems pretty straightforward but I wonder if there's any easy solution to this behavior.
TIA for your help!