% Notes, example 2.7
clear all, close all
A = im2double(imread('test_pattern.tif'));
imshow(A)
%filter impulse response
h = [0 .125 0; .125 .5 .125; 0 .125 0];
[H,f1,f2] = freqz2(h);
[F1,F2]=meshgrid(256*f1,256*f2);
%perspective mesh plot
figure,mesh(F1,F2,H);
xlabel('Horizontal frequency (c/ph)'), ylabel('Vertical frequency (c/ph)')
zlabel('Magnitude')
colormap([0 0 0]);     % use black only
set(gca,'ydir','reverse');  %make v axis point downward
%contour plot
v=0:.1:1.;             % contours will be from 0 to 1 in steps of 0.1
figure, [C,hc]=contour(F1,F2,H,v); % generate the contour plot, including values to label contours
axis square;  %make the plot square
colormap([0 0 0]);     % use black only
xlabel('Horizontal frequency (c/ph)'), ylabel('Vertical frequency (c/ph)')
clabel(C,hc)             %label the contours
title('Contour plot of frequency response of the filter of Example 2.7')
set(gca,'ydir','reverse');  %make v axis point downward
B = conv2(A,h,'same');
figure,imshow(B)