We have a problem with generating thumbnails for large PNG files (10300 x 6000 and so on) in our intranet installation of MW 1.17.0. I've got a "Error creating thumbnail: Invalid thumbnail parameters" error.
Generation of JPG thumbs for big files works fine, generation of medium PNG files (2550 x 3510) works well too.
$wgMaxShellMemory and $wgMaxShellFileSize are set to "unlimited".
How can we find a bottleneck?