MapPat.bmp pattern masking

[Vance]

Can someone explain how the RGB values in the MapPat.bmp and MapPatA.bmp files and the map backround are combined to give the color that is actually displayed on the screen?

When I make the MapPat.bmp and MapPatA.bmp black I get the map background, when I make MapPatA.bmp white I get the color of MapPat.bmp regardless what the map background is.

I have been experimenting with making MapPatA.bmp grey, to make MapPat.bmp semi transparent, but then I got a bright mangenta or cyan.

I suspect it is a simple AND, OR or XOR bit pattern masking, but what is the formula?

[Vance]

Anyone? Bil H?

[Arjuna]

Paul,
 
Can you advise on this please?

[Banquet]

Just found this on a search. I'm having the same problem.. can anyone advise the answer?

[Banquet]

Hmm, found this in an earlier discussion.. seems to be the reason;

'Some levels of transparency cause corruption, you'll have to experiment to see what works at each zoom level.

Regards
33'