%Study of DCT quantization using JPEG 
clear all
b = im2double(imread('barb.tif'));
npix = prod(size(b));
k=0;
for Q = 10:3:100
    k=k+1;
    imwrite(b,'barbTemp.jpg','quality',Q);
    bhat = im2double(imread('barbTemp.jpg'));
    %Compute PSNR
    MSE = sum(sum((b-bhat).^2))/npix
    PSNR(k) = 10*log10(1/MSE);
end
Qlist = 10:3:100;
plot(Qlist,PSNR)
xlabel('JPEG Quality parameter')
ylabel('PSNR')
title('PSNR as a function of parameter Q for JPEG quantization')