The photo-authentication product, which will be part of a plug-in for Photoshop’s 2008 edition, comes in response to a recent backlash over a doctored image of fighting in Lebanon. Reuters, which published the photo last year, learned that one of its freelance photographers had doctored the image using Photoshop when political blogger Charles Johnson of Little Green Footballs unmasked the fraud. The wire service since cut all ties with the photographer and purged his photos from its archives.
In the aftermath of the scandal, Reuters, Canon and Adobe have since teamed with forgery specialist Hany Farid of Dartmouth College to develop tools that would allow users to discover if an image had been altered using Photoshop.
“Fundamentally, our values as a company require us to build tools to detect tampering, not just create tampering,” said Dave Story, vice president of product engineering at Adobe.
Among the tools expected to be included in the 2008 edition of Photoshop are a “clone stamp,” which would allow users to identify when two areas in a photo are “impossibly similar.”
Adobe also is working on a tool that allows photo editors to trace an image back to an individual camera in much the same way ballistics experts are able to match a bullet to a gun.
Farid said the tool that allows users to determine if a photo has been altered works by examining the color in an image. Cameras don’t record all the pixels needed for a color image, but rather estimate some colors through a process known as demosaicing, or color reconstruction.
The color reconstruction process creates connections between pixels, but “when an image is retouched, it is likely that these correlations will be destroyed,” Farid said. “As such, the presence or lack of these correlations can be used to authenticate an image, or expose it as a forgery.”