diff -urN pngnq/pngnq-0.3/neuquant32.c pngnq/pngnq-0.31/neuquant32.c
--- pngnq/pngnq-0.3/neuquant32.c	2004-09-14 00:00:00.000000000 +1000
+++ pngnq/pngnq-0.31/neuquant32.c	2006-06-17 09:19:54.000000000 +1000
@@ -382,7 +382,7 @@
 	alphadec = 30 + ((samplefac-1)/3);
 	p = thepicture;
 	lim = thepicture + lengthcount;
-	samplepixels = lengthcount/(3*samplefac);
+	samplepixels = lengthcount/(4*samplefac); /* Fixed sample factor bug 17/06/2006 Stuart Coyle */
 	delta = samplepixels/ncycles;  /* here's a problem with small images: samplepixels < ncycles => delta = 0 */
 	if(delta==0) delta = 1;        /* kludge to fix */
 	alpha = initalpha;