Add or remove noise at will

The command-line version breaks down the --quality option into two sub-options (which default to the same value as --quality):

• --motion-quality=80 controls how aggressive temporal and spatial denoising is. Lower values make files smaller by reducing differences between frames, but too-low values will make animations look wobbly, jerky, or posterized.

• --lossy-quality=80 controls lossy LZW compression. Lower values make files smaller by skipping inconvenient-to-compress pixels, but too-low values will make animations look dithered and grainy.