Reference: pmHSVSplit

Essentially, the pmHSVSplit function extracts the hue, saturation, and value components of a pixmap.

pmHSVSplit(pm, h, s, v), where pm is a pixmap, creates three new pixmaps, named h, s, and, v (which have to be strings representing valid identifiers), where h, s, and v are copies of pm, but

 * h has all saturation and value components equal to unity,
 * s has all hue and value components equal to zero and unity, respectively, and
 * v has all hue and saturation components equal to zero and unity, respectively.