% manipulate.m
% read and manipulate images
dat = imread('test_image.tif');

figure()
image(dat)
title('original')

% invert colors
dat2 = 255-dat;
figure();
image(dat2);
title('inverted colors');

% gamma-correction
gamma_r = 2.2;  % gamma correction red channel
gamma_g = 2.0;  % gamma correction green channel
gamma_b = 1.0;  % gamma correction blue channel

dat2(:,:,1) = uint8( (double(dat(:,:,1))/256).^gamma_r *256);
dat2(:,:,2) = uint8( (double(dat(:,:,2))/256).^gamma_g *256);
dat2(:,:,3) = uint8( (double(dat(:,:,3))/256).^gamma_b *256);
figure();
image(dat2);
title('gamma-corrected');

% blur filter for central 301x301 pixels
alpha =0.8;
N = 30;
dat2 = double(dat);
[height,width] = size(dat(:,:,1));
cx = round(width/2);
cy = round(height/2);
for n=1:N
   tmp = 1/(1+4*alpha) * (        dat2(cy-150:cy+150,cx-150:cx+150,:) + ...
                           alpha*(dat2(cy-150-1:cy+150-1,cx-150:cx+150,:)+ ...
                                  dat2(cy-150+1:cy+150+1,cx-150:cx+150,:)+ ...
                                  dat2(cy-150:cy+150,cx-150-1:cx+150-1,:)+ ...
                                  dat2(cy-150:cy+150,cx-150+1:cx+150+1,:)));
   dat2(cy-150:cy+150,cx-150:cx+150,:) = tmp;
end
dat2 = uint8(dat2);
figure();
image(dat2);
title('blurred');