How to fix error in port widths or dimentions on the reshape block input?
I need to make DCT image compression in Simulink. Image size by default has 3 dimensions, so I used reshape tool to remove the third dimension. Color Space Conversion tool only accepts 3 dimensional images, so I used reshape again. When I try to run the simulation, I get two following errors: Error in port widths or dimensions. 'Output Port 1' of 'untitled/2-D IDCT' is a [512x512] matrix. Error in port widths or dimensions. 'Input Port 1' of 'untitled/Reshape1' has 786432 elements. This port does not accept the dimensions (or orientation) specified by the input signal. I thought reshape was supposed to accept any matrix as an input.
Prashant Kumar answered .
2025-11-20
inputNumel = prod([512,512,3])
inputNumel =
786432
Your desired output has this 1/3 as many elements.
outputNumel = prod([512,512])
outputNumel =
262144
Since you are trying to change then number of elements, the reshape block is throwing an error.
One approach to solve this is to put the following code into a MATLAB Function block
function [Y,Cb,Cr] = splitData(u)
Y = u(:,:,1);
Cb = u(:,:,2);
Cf = u(:,:,3);
end
But there is probably a simpler way to achieve your high level goal using capabilities of Image Processing Toolbox.