How to solve "Error using .* Matrix dimensions must agree."?

My code is to use Hormomorphic filtering.But i am having an error like matrix dimension must agree.I read many answers related to this but I don't understand how to apply it to my code. My image resolution size is 1935*2400.Is it the problem or how can i solve this problem?

I = imread('cephalogram.bmp');

I = im2double(I);

I = log(1 + I);

M = 2*size(I,1) + 1;

N = 2*size(I,2) + 1;

sigma = 10;

%create the high-pass filter...

[X, Y] = meshgrid(1:N,1:M);

centerX = ceil(N/2);

centerY = ceil(M/2);

gaussianNumerator = (X - centerX).^2 + (Y - centerY).^2;

H = exp(-gaussianNumerator./(2*sigma.^2));

H = 1 - H;

imshow(H,'InitialMagnification',25);

H = fftshift(H);

If = fft2(I, M, N);

Iout = real(ifft2(H.*If));

Iout = Iout(1:size(I,1),1:size(I,2));

Ihmf = exp(Iout) - 1;

imshowpair(I, Ihmf, 'montage');

Answer 1

[Walter Roberson]

We do not know if your inage is rgb (3 dimensions) or grayscale (2 dimensions)

You construct H to be nearly twice the size of the image but you expect to be able to do element by element multiplication between the two.

[Nayana R]

It is rgb image.I convert it to gray image and it worked.Thank you Walter Roberson.