CODEWITHSUNDEEP
matlabimage-processing
diegoaguilar
diegoaguilar

Reputation: 8376

How to perform image arithmetic for distinct size images in Matlab?

I'm trying to perform simple arithmetic operations like sum, difference, division, and, etc to images.

An example of what I'm doing is:

function I = difference_matlab(source1, source2)
image1 = rgb2gray(imread(source1));
image2 = rgb2gray(imread(source2));
I = mat2gray(image1 - image2);

subplot(2,2,1)
imshow(image1)
subplot(2,2,2)
imshow(image2)
subplot(2,2,3:4)
imshow(I);

end

However this will fail when images are not same size, how can I overlap images so operations are performed in common area? That's something like take smaller image and mount it over bigger, cropping operations region. However I can't figure out how to do it with out looping each image matrix.

Upvotes: 0

Views: 90

Answers (1)

mischa.mole
mischa.mole

Reputation: 357

To crop both images to the size of the smaller one (or also to the smallest size in X, Y and Z direction):

function I = difference_matlab(source1, source2)
image1 = rgb2gray(imread(source1));
image2 = rgb2gray(imread(source2));

minsize=min([size(image1); size(image2)], [], 1);

image1=image1(1:minsize(1), 1:minsize(2), 1:minsize(3));
image2=image2(1:minsize(1), 1:minsize(2), 1:minsize(3));

I = mat2gray(image1 - image2);

subplot(2,2,1)
imshow(image1)
subplot(2,2,2)
imshow(image2)
subplot(2,2,3:4)
imshow(I);

end

To pad the smaller one with zeros:

function I = difference_matlab(source1, source2)
image1 = rgb2gray(imread(source1));
image2 = rgb2gray(imread(source2));

maxsize=max([size(image1); size(image2)], [], 1);

image1_padded=zeros(maxsize);
image2_padded=zeros(maxsize);

image1_padded(1:size(image1, 1), 1:size(image1, 2), 1:size(image1, 3))=image1;
image2_padded(1:size(image2, 1), 1:size(image2, 2), 1:size(image2, 3))=image2;

I = mat2gray(image1_padded - image2_padded);

subplot(2,2,1)
imshow(image1)
subplot(2,2,2)
imshow(image2)
subplot(2,2,3:4)
imshow(I);

end

No idea if there is a more elegant solution for the zero padding, but I think it should do the trick!

pick what you like more :-)

Upvotes: 2

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