diff -urN netpbm-10.51.00-orig/converter/other/pamrgbatopng.c netpbm-10.51.00/converter/other/pamrgbatopng.c
--- netpbm-10.51.00-orig/converter/other/pamrgbatopng.c	2006-08-19 12:12:28 +0900
+++ netpbm-10.51.00/converter/other/pamrgbatopng.c	2011-01-03 19:36:21 +0900
@@ -97,6 +97,8 @@
 
     png_set_error_fn(pngP, NULL, &pngErrorHandler, NULL);
 
+    png_set_compression_level(pngP, Z_BEST_COMPRESSION);
+
     infoP = png_create_info_struct(pngP);
     if (!infoP)
         pm_error("Could not allocate PNG info structure");