clear all
close all
format compact
format long

A=imread('image/lenna.jpg');
A(506:512,506:512)
A(506:512,506:512)-128
double(A(506:512,506:512))-128

fprintf('Press to continue... \n')
pause

imshow(A)

fprintf('Press to continue... \n')
pause

B=A;
B(20:50,20:50)=0;
figure
imshow(B)

fprintf('Press to continue... \n')
pause

C=double(B)/255;
figure
imshow(C)

fprintf('Press to continue... \n')
pause
figure
imshow(double(B))