Left: original pic, highlights in statue appear blown out. Middle: ppmhsy -H
0.1. Highlights look better. Right: ppmhsy -H 1. Illustrates which parts of
the picture are considered highlights.
Hue specific saturation can be used to emphasise or de-emphasise certain parts of a picture.
Left: original. Right: greens and cyans deaturated, ppmhsy -2 0.5 -3 0.5, to
de-emphasise the background.