Here you go...
maskcolour=$FF000000 ; (Black) imgwidth=ImageWidth(sourceimage) imgheight=ImageHeight(sourceimage) LockBuffer ImageBuffer(sourceimage) LockBuffer BackBuffer() For y=0 To imgheight-1 For x=0 To imgwidth-1 rgb=ReadPixelFast(x,y,ImageBuffer(sourceimage)) If rgb<>maskcolour Then WritePixelFast(x,y,rgb,BackBuffer()) Next Next UnlockBuffer ImageBuffer(sourceimage) UnlockBuffer BackBuffer()