Identifying Manipulated Images 162
Jamie found a cool story at MIT Tech Review. (As an aside, it sits behind an interstitial ad AND on 2 pages: normally I reject websites that do that, but it's a slow news day, so I'm letting it through.)
Essentially, software is used to analyze light patterns in still photographs. Once you can figure out where the light sources are, it becomes a lot easier to determine if an image has been photoshopped.
Steganography (Score:4, Insightful)
Expert User Required (Score:1, Insightful)
So basically, if you want an image to be doctored, you use one set of values. If you want an image to be genuine, you use another set of values. Maybe somebody else's requirements differ from mine, but this is not the kind of flexibility I want in a tool that is supposed to tell me if an image has been altered or not.
For an example of a better tool, see this article [slashdot.org] from Slashdot in August 2007.
Goes both ways (Score:5, Insightful)
Adds a step for the photoshoppers (Score:4, Insightful)
Re:Limited utillity (Score:3, Insightful)
Re:Based on the same codebase, in fact (Score:0, Insightful)
changing the light source in a picture requires that you might have to desaturated some pixels and guess what their level/color might be, which is information you probably don't have available.
Re:Adds a step for the photoshoppers (Score:0, Insightful)
It's just another tool which requires (some) human ingenuity to use effectively and thus requires (just a little more) human ingenuity to use offensively. After all, you only need to miss one detail to be found out... and hiring a photodoctoring expert is something you don't want to do if you (e.g. news media) are trying to sneak this past the public. I'd say that it's not as symmetric as you suggest.
You can come up with a lot of confounding examples for this method anyway - imagine if one of the subjects in your photo has a flashlight, or is illuminated by a spotlight. "Make undetectable from light source analysis" (or "Detect Forgery by Light Source Analysis" for that matter) is something I'll expect to see in CSI, not reality.
Re:Good (Score:4, Insightful)
Re:Good (Score:5, Insightful)
Are you sure now, that you want to discourage people from using "photoshop" as a verb?
"photoshopped"? (Score:3, Insightful)
This post has been gimped by the gimper
Re:Detector == Quality Control (Score:3, Insightful)