Reference: pmHSVCombine

Essentially, the pmHSVCombine function creates a pixmap whose hue, saturation, and value components are taken from three different pixmaps.

pmHSVCombine(H, S, V) creates a pixmap P such that

 * the hue component of pixel (i, j) in P is equal to the hue component of (i, j) in H,
 * the saturation component of pixel (i, j) in P is equal to the saturation component of (i, j) in S, and
 * the value component of pixel (i, j) in P is equal to the value component of (i, j) in V.

The pixmaps H, S, and V need to have the same dimensions, and P will also have these dimensions.