man set_write_alpha_blender () - Enables the special alpha-channel editing mode. Allegro game programming library.
NAME
set_write_alpha_blender - Enables the special alpha-channel editing mode. Allegro game programming library.
SYNOPSIS
#include <allegro.h>
void set_write_alpha_blender();
DESCRIPTION
Enables the special alpha-channel editing mode, which is used for drawing alpha channels over the top of an existing 32-bit RGB sprite, to turn it into an RGBA format image. After calling this function, you can set the drawing mode to DRAW_MODE_TRANS and then write draw color values (0-255) onto a 32-bit image. This will leave the color values unchanged, but alter the alpha to whatever values you are writing. After enabling this mode you can also use draw_trans_sprite() to superimpose an 8-bit alpha mask over the top of an existing 32-bit sprite.