How to find the error image?

Question

I\'ve got a problem with image processing, but I don\'t know how to solve it.

I have 2 pictures: - Pic 1: http://goo.gl/BBxVl - Pic 2: http://goo.gl/X0VFW

Th

Answer 1

My idea also starts with the absolute difference between both images. The issue here is that you might get a lot of regions that weren't modified at all, due to compression and the inner working of some file formats (like jpg). For instance, here are two sample images and the binary difference between them to highlight every modified point, although I only manually modified the visible rectangles. In the non-binary difference you hardly notice all these points, but they are there. A threshold solves the problem here, I played with the value 20:

Now, to determine which of the images is the "good" one, I used an inpainting algorithm (you can find one such implementation at http://www.cc.gatech.edu/~sooraj/inpainting/). The reasoning for this is that the final in-painted image is more likely to resemble the image before inpainting if it does not contain the artificial patches. So, the "bad" image is the one with greater difference after the inpainting process. For this, you calculate again the absolute difference, now between the inpainted image and the original one for both cases. Then use some measure in the regions with absolute difference > 0. A dummy sum of the intensities in grayscale, in this example, gives 424454 for the image without the rectangles and 758366 for the other one.

Here is the masked image for in-painting, the "good" image inpainted, the "bad" image inpainted, and the respective absolute differences in grayscale: