About covariance using at image inpainting

Hello,everyone!

I'm just confused about covariance.

And I'll show you my code first.

% I means input learning sample image.

% X means the imupt images pixel value reshape.

for

│ ...(this part is not important so ignore it)....

│I(:,:,ii) = imread(fname);

│

│X(:,ii)=reshape(I(:,:,ii),307200,1);

│

end

and next step I'm going to covariance X this matrix,but when I write

cov(X) or cov(X(:,ii)) always fault

and it say "MTIMES is not fully supported for integer classes. At least one input must be scalar. To compute elementwise TIMES, use TIMES (.*) instead."

May someone can answer me this question, thanks!