Posts Tagged ‘jpegrotation’

Why You Should Always Rotate Original JPEG Photos Losslessly

Recognize the warning message above? It’s what Windows XP would show whenever you tried to rotate a JPEG image 90° using the Windows Picture and Fax Viewer. If you’re like me, you probably didn’t think twice about it (and checked the checkbox), since you had done it many times already and hadn’t noticed any difference in quality. After all, how hard can it be to turn a digital photo sideways? You just move the pixels around right?

Well, not really. The fact of the matter is, JPEG is a “lossy” compression algorithm that’s geared towards storing and sharing photos without taking up too much disk space. Rotating these compressed images is usually done by decompressing, rotating, and then re-compressing. Since the re-compression is lossy (i.e. data is thrown away), this process results in slightly degraded photos (hence that warning).
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