SNR for color Image

Here I have written a code for noise filteration of an color image.As image is attached here.

code is given as: here we are using geometric mean filter to reduce noise.Now I need to compute its SNR and PSNR can you please help me how can i compute it. although I can do it by taking ratio of the average signal value to the standard deviation of the background. or by using signal divided by RMS noise.where signal is diffrence between mean of signal and mean of background. so how can I compute mean and standard deviation of background??

Hope to get your response soon.Thank you very much.

K = imread('1.jpg'); subplot(1,3,1),imshow(K),title('original image'); I=imnoise(K,'gaussian'); subplot(1,3,2),imshow(I),title('Image with gaussian noise'); x=double(K); x=y; y(1, : )=x(1, : ); y(1:512,1)=x(1:512,1); y(512,: )=x(512,: ); y(1:512,512)=x(1:512,512); for k=2:511 for j=2:511 y(k,j)=(x(k-1,j-1)*x(k,j-1)*... x(k-1,j)*x(k+1,j)*x(k,j)*... x(k+1,j-1)*x(k-1,j)*x(k+1,j+1)*... x(k,j+1))^(1/9); end end W=uint8(y); subplot(1,3,3),imshow(W),title('geometric mean filtered image');

[Image Analyst]

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