void RGBtoCMYK (r, g, b, c, m, y, k) COLOR.C Level 13
int r, b, g The input red, green, and blue vectors (063).
int *c, *m, *y, *k Pointers to the output cyan, magenta, yellow and black vectors (063).
This routine converts colors in the RGB representation to the CMYK representation that is usually used for four-color printing.