how can i calculate MSE and PSNR of RGB color image

i embeded a watermark in RGB color image now i want to calculate PSNR and MSE of original and watermarked images . how can i find PSNR and MSE of original and watermarked images

[Aniket Paranjpe]

How to compute three PSNR Values , one for each channel?

[siva shangari]

how to compute mean and variance for each channel?

Answer 1

[B.k Sumedha]

clc;

[filename1,pathname]=uigetfile('*.*','Select the original image'); 

image1=imread(num2str(filename1));

[filename2,pathname]=uigetfile('*.*','Select the watermarked image'); 

image2=imread(num2str(filename2));

figure(1);

imshow(image1); title('Original image'); 

figure(2);

imshow(image2); title('Watermarked image');    

[row,col] = size(image1)

size_host = row*col;

o_double = double(image1);

w_double = double(image2);

s=0;

for j = 1:size_host; % the size of the original image

s = s+(w_double(j) - o_double(j))^2 ; 
end

mes=s/size_host;

psnr =10*log10((255)^2/mes);

display 'Value of',psnr

[AKSHAY PUSHPAD]

While using above mentioned program..i am getting this error command.. Error: File: Untitled.m Line:4 column: 11 Unexpected MATLAB operator.

What does this mean??

[Image Analyst]

Looks okay to me. You might try my attached demo instead and see if that works.

[Atika Nugraheni]

why I only got the result of PSNR is one value? why does it not give 3 value? the format of both images is RGB, right? and how to show the value of MSE?

[Image Analyst]

I don't know what code you ran. Make sure you're running it only one color channel at a time and do it for each color channel if you want 3 PSNR's out.

[Atika Nugraheni]

Ok Thankyou

[Atika Nugraheni]

I want to ask, actually if both images is RGB, then the MSE value consist of 3, MSE for Red, Green, and Blue. And how about the PSNR of the RGB image? The correct way, Is the PSNR produce three value of color channel or just one value used the average of MSE? Please explain.

[Image Analyst]

They're both 3 values - one for each color channel. You can average them together, if you want, to produce one number. Whatever meets your needs.

[Atika Nugraheni]

Is it possible if the result of PSNR is negative? Because I obtained the value of PSNR is negative. If the MSE result is high then the PSNR result is low? am I right? Please explain. thankyou

[Walter Roberson]

Yes, if the signal power is less than the noise power.

https://www.researchgate.net/post/Can_anyone_explain_why_psnr_values_between_images_come_in_negative_values_and_snr_are_positive

[Chidiebere Ike]

@ Image Analyst...I observed that the attached PNSR code is for Gray scale images, it this code applicable to Color images ?? also

[siva shangari]

@Image Analyst... how to compute mean and variance for each channel?

[Walter Roberson]

mean(YourSignal,2)  %mean over columns
var(YourSignal, [], 2)  %variance over columns

If "channel" means color pane in this case, then

mean(YourSignal, [1 2])
var(YourSignal, [], [1 2])