Matrix dimensions must agree error when using DCT2?

Hi I am trying to use the dct2 function on some images. When I try to use the following code, I get the error "Matrix dimensions must agree," any ideas? Here's my code:

A = imread('IC1.png');
imshow(A);
D = dct2(A);

I am aware that I can get this to work if I use rgb2gray however I want to compress rgb images, is this not possible?

Answer 1

[Abhishek Gupta]

Hi Harry,

The 'dct2' function takes only a 2-D numeric matrix as input. Please see the documentation for more details: -

https://www.mathworks.com/help/images/ref/dct2.html#d122e38105

I am referring you to the following File Exchange link, which might resolve your issue: -

https://www.mathworks.com/matlabcentral/fileexchange/24050-multidimensional-discrete-cosine-transform-dct