make_trans_font - Man Page
Makes a font use transparency. Allegro game programming library.
void make_trans_font(FONT *f);
This function converts a font to use transparency for drawing. That is, each glyph in the font will be drawn with draw_trans_sprite, so you can use the same blenders as with draw_trans_sprite to draw the font. One common use of this is to load a bitmap font with an alpha channel, and therefore get anti-aliased text output by using Allegro's alpha blender. Here's an example how to do that:
FONT *f = load_font("alphafont.tga", NULL, NULL); make_trans_font(f); set_alpha_blender(); textprintf_centre_ex(screen, f, 320, 240, -1, -1, "Anti-aliased Font!");
is_trans_font(3), set_alpha_blender(3), load_font(3), draw_trans_sprite(3)
version 4.4.3 Allegro manual