You don't really need to define your own code for copying one pixmap onto another - Blitz already provides pixmap windows/static pixmaps, where you can say that one pixmap is a window within an existing 2nd pixmap, and then using pixmap.paste should I presume clip to the window. Whether you call memcopy to copy a whole row of pixels, or do it in your own loop, probably isn't much different seeming as the bottleneck is memory accesses.