#	pngscale - scale a png image
.	Net
(	in out
|	in1 in2 image mask image2 mask2
*	tee	tee	<in in1> >in2
*	to_pnm	pngtopnm	<in1 >image
*	to_mask	pngtopnm	<in2 -alpha >mask
*	scale1	pnmscale	$scale <image >image2
*	scale2	pnmscale	$scale <mask >mask2
*	to_png	pnmtopng	<image2 -alpha mask2< >out