How to compare histogram of two different images.

I want to compare histogram value of two different images. like i want to compare two different matirces of the histogram vaues and based on the values i can say they are same image or not.

[Walter Roberson]

subplot(1,2,1);
img = imread('cameraman.tif');
imshow(img);
subplot(1,2,2);
img2 = sort(sort(img,1),2);
imshow(img2);

Are those "same image"? They have all the same data, so their histograms are going to be identical.

[Ravi Singh]

Yes the images are same so is it like the values of the histogram would be identical for same images or completely different for different images ?

[Walter Roberson]

I would suggest to you that the two, img and img2, are in fact different images.

I would also suggest to you that if you were to take img and make a version that is half as bright (so same relative distribution of values, but half the absolute value) that the result would arguably be the "same" image, or at least the same scene. (If you were to photograph exactly the same scene twice with one f-stop difference, then one image would be half as bright as the other, but it would be the same scene and so a case could be made that it is the same image.)

[Ravi Singh]

Thanks for kind help. i would like to know can i put some kind of expressions on the values of two histograms to say if its matches some perentage amount of the values then its the same image?

[KALYAN ACHARJYA]

like i want to compare two different matirces of the histogram vaues and based on the values i can say they are same image or not.

There may be possibility of having same (exactly) histograms of two completely different images. Histogram values are independednt with respect to pixel coordinates.