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April 5, 2010 2:40 AM Subscribe
Image Error Level Analyser
Digital photography and associated software tools have made it trivially easy
to manipulate the images and media messages that we consume on a daily basis (previously
and more recently
While some individuals have adopted more unique approaches
to getting to the truth behind a photo, the JPEG image format's inherent "lossiness
" — like a photocopy, the fidelity or quality of the original is reduced on subsequent re-saves — opens up the opportunity to learn if and how an image has been doctored.
Dr. Neal Krawetz's error level analysis
(PDF) technique describes resaving a JPEG image and using principal component analysis
to measure the difference between original and resaved images, highlighting "hot" areas that suggest manipulation.