--- Imaging-1.1.4/PIL/PngImagePlugin.py.orig	2003-05-07 05:44:17.000000000 +0900
+++ Imaging-1.1.4/PIL/PngImagePlugin.py	2005-03-04 22:42:37.000000000 +0900
@@ -424,6 +424,10 @@
           chr(0),                               # 11: filter category
           chr(0))                               # 12: interlace flag
 
+    #print 'PngImagePlugin:mode=', im.mode
+    if im.mode == "RGBA":
+        chunk(fp, "bKGD", "\000\377\000\377\000\377")
+
     if im.mode == "P":
         chunk(fp, "PLTE", im.im.getpalette("RGB"))