Found out something odd about your image resizing code today. I just uploaded my first photo, showing progress of one of my miscreants, and upped it at 1280x960 and 287 kB.

Your site has resized it to 900x675. From what you were saying earlier I now assume that 900 is the actual limit for resized width, rather than 800. Does this also apply to height? Reason I ask is that I've done so much image optimisation in my time that I personally don't mind what the limits are. I can easily resize to suit anyway.

The second point is that although I uploaded at 287 kB, your code has reprocessed the image to 428 kB. So your resize code has cut the pixels down, but has simultaneously increased the download burden for your site by approximately 50%*.

If I'd resized it to 900x675 myself, I could have done the same image at just under 160 kB with no discernible loss of quality.

In other words, if somebody does upload an image suitably optimised for use on a website (ie: .jpg format, saved on medium quality setting) your existing code will nevertheless reprocess it to be less optimal. This seems like a bad idea.

So next question: if an image is upped at < 900px in size, will your resize algorithm just accept it without reprocessing, or will it reprocess anyway? If the former, then there's benefit in people sorting it before uploading. If the latter, then there's really no point in people sorting it themselves, because it'll be a wasted effort.

*For the non-techy types, bandwidth usage is directly related to image size in bytes, not to image size in pixels. Pixels don't matter for bandwidth (although they do matter for browser RAM if you want to go down that rabbit hole, but that's not the website's problem).