Calculating the MSE with a RGB and grayscale image in MATLAB - Image Processing -

how calculate mse rgb , grayscale image in matlab? have written code here:

i = imread('iris.jpg); gray = rgb2gray(i); n = size(i); m = n(1); n = n(2); mse = sum(sum(i-gray).^2))/(m*n); fprintf('\nmse:%7.2f',mse); 

however, when run code, error:

error using - matrix dimension must agree.

how fix error?

i'm not sure why you'd want this.... since grayscale , colour images different each other in terms of colour values.

the error you're getting quite clear. grayscale image has 1 channel while rgb image has three. trying subtract images of incompatible dimensions , error.

however, if mse calculation want, need make sure grayscale image has 3 colour channels. grayscale images have red, green , blue components equal, , simple fix repmat should trick. can use duplicate grayscale image on multiple channels simulate colour image.

do gray variable before computing mse:

gray = repmat(gray, [1 1 3]); 

as such, doing this. btw there typo in first line. forgot closing quote mark. have additional closing brace mse calculation happening.

i = imread('iris.jpg'); gray = rgb2gray(i);  %// change  gray = repmat(gray, [1 1 3]);  n = size(i); m = n(1); n = n(2); mse = sum(sum(i-gray).^2)/(m*n); fprintf('\nmse:%7.2f',mse); 

be warned high mse because grayscale values different original rgb values.

as side note, if don't repmat, can achieve same thing bsxfun automatically broadcasts grayscale image on multiple channels you:

i = imread('iris.jpg'); gray = rgb2gray(i);  n = size(i); m = n(1); n = n(2); mse = sum(sum(bsxfun(@minus, i, gray).^2))/(m*n); %// change fprintf('\nmse:%7.2f',mse);