16 bit FPG loading ignores transparency

[Joseba Echevarria García]

Loading 16 bit FPG files ignores the transparency info in maps. Color 0 in 16bit maps is interpreted as "transparent" in BennuGD, but is drawn as rgb(0, 0, 0).

The following code illustrates the problem, when run with the attached FPG file.

import "mod_map"
import "mod_draw"
import "mod_video"
import "mod_key"

Process main()
Begin
    set_mode(640, 480, 32);
    map_clear(0, graph, rgb(0, 255, 0));
    file = fpg_load("file.fpg");
    graph = 1;
    x = 320; y = 240;
    while(!key(_esc))
        FRAME;
    end
End