Image forensics software

Question

I'm not really sure if this question belongs here, however I didn't find it fitting well into photography nor stackapps.

I'm looking for a software I've seen some long time ago on Discovery channel. There was a series about some pictures found on Internet. Presenter was analyzing these images to proof whether they were real or not. I can recall analysis of pictures like:

• Videos with some really incredible basketball tricks and shots:

  

• this video

AFAIR, he was using this software on Mac OS X system. I remember one feature he frequently used: ability to analyze light incident angle.

I would also love suggestions on similar apps (open-source ones preferably, but other are also welcome).

Answer 1

There's one neat trick that you can do in almost any image editing software (I used Photoshop). I've read about an automated implementation in a paper once, but I forgot where I found it.

For an interesting read, check this: H.T. Sencar and N. Memon - Overview of State-of-the-Art in Image Forensics

Copying and pasting from different (JPEG) sources, rescaling and then re-saving the file in JPEG (but also lossless compression) often results in visible differences between block artefacts. This is no guarantee that an image was faked, but in many cases you can identify it that way. Go ahead and change the midtones:

Then you are likely to see these differences: