GD problems with opacity on translucent background

Hi, I have a little problem with a script I am trying to make. The main problem is that when I draw something on a translucent png created with gd, it will still take the color which was set as transparent color. For a demo look at http://www.cranberries-fan.com/images/transparent/test.php The backgroundcolor is set to black so in the black box it seems to be ok, but in the yellow box you can see that the transparentcolor is blended over black :-( while the empty spaces around the circle is actually translucent. Am I doing something wrong? I read something on the net about the bundled gd having a bug compared to this issue, so I installed php 4.3.6 this morning so that the GD lib would have version 2.0.22 GD Support enabled GD Version bundled (2.0.22 compatible) FreeType Support enabled FreeType Linkage with freetype T1Lib Support enabled GIF Read Support enabled JPG Support enabled PNG Support enabled WBMP Support enabled XBM Support enabled look for the script at http://www.cranberries-fan.com/images/transparent/genimage.phps What am I doing wrong or what is the GD lib doing wrong?