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This is really a two part question, since I don't fully understand how these things work just yet: My situation: I'm writing a web app which lets the user upload an image. My app then resizes to something displayable (eg: 640x480-ish) and saves the file for use later. My questions: Given an arbitrary JPEG file, is it possible to tell what the quality level is, so that I can use that same quality when saving the resized image? Does this even matter?? Should I be saving all the images at a decent level (eg: 75-80), regardless of the original quality? I'm not so sure about this because, as I figure it: (let's take an extreme example), if someone had a 5 megapixel image saved at quality 0, it would be blocky as anything. Reducing the image size to 640x480, the blockiness would be smoothed out and barely less noticeable... until I saved it with quality 0 again... On the other end of the spectrum, if there was an image which was 800x600 with q=0, resizing to 640x480 isn't going to change the fact that it looks like utter crap, so saving with q=80 would be redundant. Am I even close? I'm using GD2 library on PHP if that is of any use

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