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Old 19-01-2008, 23:21   #12 (permalink)
Dave Canon
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Re: Cropping without affecting quality?

Silkstone, your test will not really reveal the problem with resaving JPEGs. If you open then save the same unedited image any deterioration will be minor. However, if you edit the picture (even minor editing) then the input to the JPEG algorithm is different and a different set of approximations takes place. You only need to do this about 6 - 8 times to seriously damage the image. See the two examples below of a JPEG image before and the same image saved 8 times with very minor editing. You may not be able to see the editing but you can see the artifacts on the instrument and music.

Before



After

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