
gives a newspaper-ish look, a useful special effect.

<P>The <B>-value</B> option alters the thresholding value for
Floyd-Steinberg and simple thresholding.  It should be a real number
between 0 and 1.  Above 0.5 means darker images; below 0.5 means
lighter.

<P>The Hilbert curve method is useful for processing images before
display on devices that do not render individual pixels distinctly
(like laser printers).  This dithering method can give better results
than the dithering usually done by the laser pr