I'm guessing you want to use JPEGs to make sure that older browsers can view them, as the files will be bigger than PNGs and the images not as crisp (I'm still pissed about losing the GIF format as I do a lot of calculated (non-photographic) images).

I just tested this out using the sample code from the GD Synopsis, and indeed  print $im->jpeg; creates a JPEG, but the odd thing was it appeared to be different from the PNG created with the same code. So, I think for a moment that this isn't right, and I try opening both images in the same viewer (our IT drones recently installed "Microsoft Photo Editor" here and it grabbed the PNG extension but not the JPEG). Sure enough, the files are virtually identical when you discount the fundamental difference between lossy and lossless formats, but MSPE had created a black and white grid on the background somehow. No matter, MSPE no longer grabs any extensions on this machine ;-).

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I'd like to be able to assign to an luser