set_alpha_blender (3) - Linux Manuals
set_alpha_blender: Enables a special alpha-channel blending mode. Allegro game programming library.
Command to display set_alpha_blender manual in Linux: $ man 3 set_alpha_blender
NAME
set_alpha_blender - Enables a special alpha-channel blending mode. Allegro game programming library.
SYNOPSIS
#include <allegro.h>
void set_alpha_blender();
DESCRIPTION
Enables the special alpha-channel blending mode, which is used for
drawing 32-bit RGBA sprites. After calling this function, you can use
draw_trans_sprite() or draw_trans_rle_sprite() to draw a 32-bit source
image onto any hicolor or truecolor destination. The alpha values will be
taken directly from the source graphic, so you can vary the solidity of
each part of the image. You can't use any of the normal translucency
functions while this mode is active, though, so you should reset to one
of the normal blender modes (eg. set_trans_blender()) before drawing
anything other than 32-bit RGBA sprites.