If you ever have a need to find out if any given digital photograph has been altered, manipulated, etc.,ÂError Level Analysis isÂa way to easily find out.
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http://errorlevelanalysis.com/
Explanation
âError level analysis (ELA) works by intentionally resaving the image at a known error rate, such as 95%, and then computing the difference between the images. If there is virtually no change, then the cell has reached its local minima for error at that quality level. However, if there is a large amount of change, then the pixels are not at their local minima and are effectively original.â
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-Neal Krawetz, Ph.D. http://www.hackerfactor.com
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This implemenation makes use of the Python Image Library, and libjpeg (v6.2.0-882.2). ELA is carried out at 95%. Resulting ELA images have had their brightness enhanced to further seperate differences out.
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Built over a lazy weekend with django. Inspired by Neal Krawetz and his image forensic work.