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While on the subject of JPEG in JavaScript, I made a web page[1] to repeatedly encode an image in order to bring out the artifacts. (Works “best” on text.)

[1] http://minimul.ro/enricher



This cheats a little by shaking the image, though. Without that you're hitting a fixed point much earlier, with less dramatic results.


I don't call it cheating... I call it simulation of the effects of cropping.

But seriously though, I was quite was surprised by how little is lost if you repeatedly encode the same image. Then again, it makes a lot of sense if you look at how blocks are encoded.


There was a nice article about that: http://www.hackerfactor.com/blog/index.php?/archives/355-How...

Turns out, not every JPEG encoder is identical in that regard and Photoshop destroys more than others.




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