Ok
I just can't see what's wrong with that function. I checked the bmap operations used in that function in both the A6 and then the A7 manual, but nothing seems to have changed, so I don't know why it's not working. I'm checking the 'beta features' page right now to see if something has changed for the pixel_for_bmap and pixel_to_bmap functions.
Anyways, try using the bmap_draw function on two pictures without an alpha channel - maybe it just doesn't draw the other alpha channel onto the picture (just a thought, but might be worth a try).
I'll let you know if I find anything on the beta-page
Edit: Didn't find anything there
Edit 2: Try initializing the variables in bmap_draw (replace "
var i;var k;var t;" by "
var i = 0;var k = 0;var t = 0;"),
and remove these lines: "
if(t - (max_loops-1) >= 0) {wait(1);t = 0;}"
Just to see if it makes any difference.