man set_color_depth () - Sets the global pixel color depth. Allegro game programming library.
NAME
set_color_depth - Sets the global pixel color depth. Allegro game programming library.
SYNOPSIS
#include <allegro.h>
void set_color_depth(int depth);
DESCRIPTION
Sets the pixel format to be used by subsequent calls to set_gfx_mode() and create_bitmap(). Valid depths are 8 (the default), 15, 16, 24, and 32 bits. Example:
set_color_depth(3); if (set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0) != 0) { abort_on_error("Couldn't set a 32 bit color resolution"); }
Note that the screen color depth won't change until the next successful call to set_gfx_mode().