What are some applications to detect altered / photoshopped images? I'm looking at a used item online and get the feeling the seller touched-up the photos (he's a graphics designer, found out from his domain name.
Two things I'm looking for are:
you can use error level analysis (ELA). its free, easy, and relatively straight forward. there is a site you can even point to an url of the image. the result is an image that shows 'new' vs 'old' pixels based on the way .jpg works iirc.
the site is http://errorlevelanalysis.com/
“Error level analysis (ELA) works by intentionally resaving the image at a known error rate, such as 95%, and then computing the difference between the images. If there is virtually no change, then the cell has reached its local minima for error at that quality level. However, if there is a large amount of change, then the pixels are not at their local minima and are effectively original.”
i don't think there is a software solution to prove photo fakery.
my advice: if it doesn't feel right, then don't do it.
If there's no EXIF information then it's likely that a photograph is not an original from a digital camera. Some manipulations must have happened.
Detecting changes in a photo is possible with proper forensics software. This is helpful when the image itself isn't showing any traces. The software works by doing pattern recognition, since digital camera's tend to have specific patterns in the pictures they create. Most image manipulations will change these patterns which can be recognised. The software should even be able to give some indications what kind of manipulations have taken place.
Where you can find this software? Well, the FBI, CIA and Interpol will be using it. Don't know if there are any commercial products available but be prepared to pay an arm and a leg for it. (I think it would be real expensive.)
Most image analysis software will be created to recognise shapes and objects. But the kind of software you need is something which can trace manipulations. It's not much more complex than recognising objects, but almost no one is interested in this kind of software. (Except of course to detect if an image is real or fake.)
It is bad that the seller is touching op those images? Maybe he just sharpened the image and removed some things from the background.
BRIGHTEN the image way up, with High contrast if things were pasted badly into the image, it usually leave a edge around it that will show up.
EXIF data won't tell you much - he might have loaded the photo into something like Photoshop just to crop it the way he wanted or some equally reasonable modification.
For Exif reading, you can use FastStone Image Viewer. [features, download link 1, download link 2]
Two screenshots [they differ because they are from different versions of FastStone]
for Detecting touch ups, eye is the best tool, I guess.
Here is a link to very informative site about photo analysis with lots of resources about technical and other aspects of photo manipulation.
