Reference: pmShiftHue
pmShiftHue(pm, h) returns the pixmap pm with the hue of all pixels increased (modulo 360) by h. The hue is a number between 0 and 360.
pmShiftHue(pm, h) returns the pixmap pm with the hue of all pixels increased (modulo 360) by h. The hue is a number between 0 and 360.