Fix from upstream for http://bugs.gentoo.org/109783

--- converter/other/pngtopnm.c
+++ converter/other/pngtopnm.c
@@ -722,7 +722,7 @@
     if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY ||
         info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
 
-        retval = TRUE;
+        retval = FALSE;
     else if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE) {
         bool foundColor;
         unsigned int i;