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How Photoshopped Is That Picture?

Posted by timothy on from the pretty-darn dept.

Freddybear writes "Digital forensics experts at Dartmouth have developed software that can analyze digital photos to rate how drastically they have been altered by digital editing techniques. 'The Dartmouth research, said Seth Matlins, a former talent agent and marketing executive, could be "hugely important" as a tool for objectively measuring the degree to which photos have been altered.'"

3 of 226 comments (clear)

  1. Too bad this requires a "before" picture by wisebabo · · Score: 5, Interesting

    If it did the analysis using just the "after" image (maybe by looking statistically at ithe ndividual pixel level, I dunno I'm not an image expert) that software would be SO useful for Internet dating sites! ;)

    Actually I'm wondering if images CAN be analyzed using statistical data from the individual pixel data to determine things like what camera was used to take the picture, maybe what software was used to edit/convert it (using gamma curves?). Then you could see (maybe) who was posting pictures of themselves from long ago (not like I've ever done that!).

  2. Re:reliably? by DeadCatX2 · · Score: 5, Interesting

    Actually, conversion is one method of detecting photoshop changes. It's called Image Error Level Analysis.

    http://errorlevelanalysis.com/

    The gist is that every time you save an e.g. JPEG, the quality will get worse. However, the worsening of quality decreases each time it is saved, eventually asymptotically approaching the worst level. Therefore, if you're working on a photoshopped picture, each time you save it the quality of the various parts of the photo will decrease by different amounts. This can be used to identify which pieces of the photo have been modified more recently than others, since they will have a different error level than the pieces that were modified first.

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    :(){ :|:& };:
  3. I wonder how it deals with in-camera processing by yeremein · · Score: 5, Interesting

    I recently got a tiny point-and-shoot camera, a Canon ELPH 300 HS, and I've been participating in CHDK's effort to hack it. When we got RAW support working, I learned the camera's lens actually has severe barrel distortion that gets "corrected" in software before saving a JPEG.

    Images are "shopped" before they even emerge from the camera these days.