bg_al            4140 ext/gd/gd.c    	int fg_al, bg_al, al;
bg_al            4183 ext/gd/gd.c    	bg_al = gdImageAlpha(bg_img, _bg);
bg_al            4189 ext/gd/gd.c    		al = bg_al + (double) (fg_al - bg_al) / aa_steps * (i + 1);