getr_depth (3) - Linux Manuals
getr_depth: Extract a color component from a color in a specified pixel format. Allegro game programming library.
NAME
getr_depth, getg_depth, getb_depth, geta_depth - Extract a color component from a color in a specified pixel format. Allegro game programming library.SYNOPSIS
#include <allegro.h>
int getr_depth(int color_depth, int c);
int getg_depth(int color_depth, int c);
int getb_depth(int color_depth, int c);
int geta_depth(int color_depth, int c);
DESCRIPTION
Given a color in the format being used by the specified color depth, these functions extract one of the red, green, blue, or alpha components (ranging 0-255). The alpha part is only meaningful for 32-bit pixels. Example:
int r, g, b, color_value, bpp; bpp = bitmap_color_depth(bitmap); color_value = getpixel(bitmap, 100, 100); r = getr_depth(bpp, color_value); g = getg_depth(bpp, color_value); b = getb_depth(bpp, color_value);