# How to validate contrast adjusting using imadjust comparing to other contrast adjusting techniques and original image?

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Nayana R on 23 Jan 2019
Edited: DGM on 9 Jul 2023
I want to compare the difference between imadjust image and original image using a specific measurement o technique.Can you suggest any technique to show the differnce between original and imadjust image?

Image Analyst on 23 Jan 2019
You can cast the images to double then subtract them to see the differences
diffImage = double(image1) - double(image2);
imshow(diffImage, []);
impixelinfo;
You can also view the values in the workspace/variable inspector - just double-click on the variable name in the workspace panel.
Nayana R on 23 Jan 2019
Nayana R on 23 Jan 2019
Can you suggest any other method to show the difference using a value of a graph?

DGM on 9 Jul 2023
Edited: DGM on 9 Jul 2023
The question and comments are vague, but this is my answer to one interpretation -- i.e. to use a graph to illustrate the transformation made to the image data. Consider a simple gamma adjustment. We should see a simple power function.
[xx idx] = sort(im2double(inpict(:)));
yy = im2double(outpict(idx));
plot([0 1],[0 1],':','color',[1 1 1]*0.5); hold on % reference line
plot(xx,yy) % the TF curve
xlim([0 1]); ylim([0 1])
axis square
grid on
Note that you'll only be able to draw the curve over the range represented by the images. Consider an image with a much lower dynamic range.
[xx idx] = sort(im2double(inpict(:)));
yy = im2double(outpict(idx));
plot([0 1],[0 1],':','color',[1 1 1]*0.5); hold on % reference line
plot(xx,yy) % the TF curve
xlim([0 1]); ylim([0 1])
axis square
grid on

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