clc;
close?all;
clear?all;

O=imread（‘model.jpg‘‘jpg‘）;
I=rgb2gray（O）;
%I?saves?the?gray?information?of?image?model.jpg

I_info=size（I）;
M=I_info（1）;?%the?width?of?the?image
N=I_info（2）;?%the?height?of?the?image
%I?saves?the?information?of?image?modelgray.jpg

imshow（I）;title（‘original?image‘）;
%display?original?image

I64=floor（I/4）*4+2;
III=double（I）;
I6464=double（I64）;
I64_mse=sum（sum（（III-I6464）.^2））/（M*N）;
mean64=sum（sum（I64））/（M*N）;
mean64_2=mean64*ones（MN）;
I64_2=double（I64）-mean64_2;
sigma2_64=sum（sum（（I64_2）.^2））./（M*N）;
I64_snr=10*log（sigma2_64/I64_mse）;
I64_psnr=10*log（255^2/I64_mse）;
fprintf（‘\nLevel=64?MSE/SNR/PSNR?are??%f?/?%f?/?%f??separately.\n‘I64_mseI64_snrI64_psnr）;
figure;
imshow（I64）;title（‘quantized?image?with?L=64‘）;
%level=64
%display?the?MSE/SNR/PSNR?and?the?quantized?image

I32=floor（I/8）*8;
I32_mse=sum（sum（（I-I32）.^2））/（M*N）;