are you shure you are using convertpixmap correctly?
the correct way is:
the new image is stored in newpixmap, pixmap will still have the original loaded image/pixmap.
the correct way is:
newpixmap:tpixmap = convertpixmap(pixmap,PF_BGRA8888)
the new image is stored in newpixmap, pixmap will still have the original loaded image/pixmap.