This is again a good hint, thanks. But the problem is I have them in imagelists.

Perhaps I could alter the Imagelsiteditor with a new method:

1) Export all images with a process number at the beginning of the filename to a temp dir
2) for %I in (*.png) do imagelisteditorpath\pngout.exe %I progress each single image
3) Clear the imagelist, reload each single image by beginning number and remove that number.

Do you know if they only get smaller on harddisk (filesize) or also in memory? Than this would be worth the effort...

Firle