Issue with CopyWindow() under OSX

1
Hi,

I'm using the latest Psychtoolbox version for OSX and I try
to:
window=Screen('OpenWindow',0, [],[],pixelSize,1);
image=Screen('OpenOffscreenWindow', window, [0 0 v(1,1)
v(1,2)]);
Screen('PutImage',image, pic1, []);
Screen('CopyWindow', image, window, [], [575 471 625
521]);

And I get following error:
INTERNAL PSYCHTOOLBOX ERROR
error: PsychError_unimplemented
general description: Feature not yet implemented
specific description: GetImage does not yet support alpha
channel.
module name: Screen
subfunction call: CopyWindow
file name:
../../../Source/Common/Screen/SCREENCopyWindow.c
function name: SCREENCopyWindow
line number: 134
??? (null)

Error in ==>
/Applications/PTB_29_Jan_04_A/PTB_29_Jan_04_A/Psychtoolbox3/Target/OSX/PsychTimingDemo/PsychFunctions/Screen.mexmac
Error in ==> /Users/wiecki/Desktop/point1.m
On line 35 ==> Screen('CopyWindow', image, window, [],
[575 471 625 521]); %endpos1(1,:), []);

Someone an idea? I didn't find anything concering the alpha
channel, is it some parameter I have to change?

Kind regards,
Thomas Wiecki