Wednesday, July 2, 2014

Digital Image Forgery Detection with Image Registration

Blending between the two images help identify the differences. (It may take a few seconds to load the gif file.) You could see that Zhao Wei's left hand was left in the digitally manipulated image.

How did we do it? 

First step, download the following two images. The first one is the poster downloaded from the official webpage (with circular marks labeled by someone else), the other is the picture taken from this link. Presumably, they are taken at the same time at the same event.

Image source: link
Image source: link

Feature Detection

We detect Speeded Up Robust Features (SURF) features (shown in the green circle) from bot images. Note that we crop part of the first image to avoid spurious features for detection and matching. 

Feature matching and Image Registration

With the detected features from the two images, we can now estimate the geometric transformation (homography) between two images using the direct linear transform and RANSAC. We can thus align the images to help better show the modification.

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