I am using FreeMat, and I have an RGB picture which is a 3D matrix contains the columns and rows of the pictures and the RGB values for each pixel.

Since there is not an intrinsic function to convert RGB picture to YIQ, I have implement one. I came up with this code:

Assume I have a 3D array, image_rgb:

matrix = [0.299 0.587 0.114;
0.596 -0.274 -0.322;
0.211 -0.523 0.312];
row = 1:length(image_rgb(:,1,1));
col = 1:length(image_rgb(1,:,1));
p = image_rgb(row,col,:);

%Here I have the problem
mage_yiq(row,col,:) = matrix*image_rgb(row,col,:);

max_y = max (max(image_yiq(:,:,1)));
max_i = max (max(image_yiq(:,:,2)));
max_q = max (max(image_yiq(:,:,3)));

%Renormalize the image again after the multipication
% to [0,1].
image_yiq(:,:,1) = image_yiq(:,:,1)/max_y;
image_yiq(:,:,2) = image_yiq(:,:,2)/max_i;
image_yiq(:,:,3) = image_yiq(:,:,3)/max_q;

I can't understand why the matrix multiplication fails. I want the code to be nice and not just to, multiply the matrix by hand...