You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: PSNR_RGB.m
    path of file: ./repos/mctc4bmi/algs_tc/BCPF/Evaluation
    
    the code of the file until where you have to start completion: function y=PSNR_RGB(X,Y)
 
% Y= PSNR_RGB(X,Y)
% Computes the Peak Signal to Noise Ratio for two RGB images
% Class input : double [0,1] ,
% july ,25, 2012
% KHMOU Youssef
 

    
function y=PSNR_RGB(X,Y)
 
% Y= PSNR_RGB(X,Y)
% Computes the Peak Signal to Noise Ratio for two RGB images
% Class input : double [0,1] ,
% july ,25, 2012
% KHMOU Youssef
 
 
 
if size(X)~=size(Y)
    error('The images must have the same size');
end