getr (3) - Linux Manuals
getr: Extract a color component from the current pixel format. Allegro game programming library.
NAME
getr, getg, getb, geta - Extract a color component from the current pixel format. Allegro game programming library.SYNOPSIS
#include <allegro.h>
int getr(int c);
int getg(int c);
int getb(int c);
DESCRIPTION
Given a color in the format being used by the current video mode, these functions extract one of the red, green, blue, or alpha components (ranging 0-255), calling the preceding 8, 15, 16, 24, or 32-bit get functions as appropriate. The alpha part is only meaningful for 32-bit pixels. Example:
int r, g, b, color_value; color_value = getpixel(screen, 100, 100); r = getr(color_value); g = getg(color_value); b = getb(color_value);