PNG encoder always rebuilds the palette to avoid losing transparency.
diff --git a/ChangeLog b/ChangeLog
index 43399b3..ed67d24 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2010-12-10 6.6.6-5 Glenn Randers-Pehrson <glennrp@image...>
+ * Make the PNG encoder always rebuild the palette, to avoid losing
+ transparency when it is out of sync with the pixel data (reference
+ http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=17655).
+
2010-12-10 6.6.6-5 Cristy <quetzlzacatenango@image...>
* Account for virtual canvas for the -flip / -flop options (reference
http://www.imagemagick.org/discourse-server/viewtopic.php?f=1&t=17626).