Find the changed area between two images

I have 3 photos taken from a sample. The first one is prior to a test and the second and third ones are taken after the test. I am intersted in finding the changed area in the painting after each test. IN other words between image number1and 2 and image number 1and3.

Image number 2 has slighty changed but image number 3 has considerably changed.

here are the photos.

Thank you

Answer 1

[Balakrishnan Rajan]

Depends on your definition of area of the painting. Is every point with colour anything but absolute white considered as a part of the painting? Assuming that anything brighter than the mid level of gray to be an unpainted region, the following code must be able to get the area of a painting:

Im = imread('File location');
ImBW = Im(:,:,2);
imshow(ImBW);
threshold = 127;
area = 0;
for i = 1 : length(ImBW(:,1))
    for j = 1 : length(ImBW(1,:))
        if(ImBW(i,j)>threshold)
            area = area+1;
        end
    end
end

Use this to compute the areas of the different images and take difference accordingly.

Hope it helps.

[Tala Hed]

I appreciate your help, but its not what I am looking for! maybe I was not clear :)

There should be comparision between the original image and the other two to detect the change between them!

Thanks