dat = imread('test_image.tif');


% reduce resolution of blue layer by factor 64 (block 8x8 pixels)

[height,width] = size(dat(:,:,1));

% down-sampling
for w=1:width/8,
for h=1:height/8,
   blue(h,w) = mean(mean(dat((h-1)*8+1:h*8,(w-1)*8+1:w*8, 3)));
end
end

image(dat); title('original');

figure()
image(dat(:,:,1)); title('red channel');
c = zeros(256,3);            % setup a color axis with red intensities
c(:,1) = 0:1/255:1;
colormap(c); caxis([0 255]);

figure()
image(dat(:,:,2)); title('green channel');
c = zeros(256,3);            % setup a color axis with green intensities
c(:,2) = 0:1/255:1;
colormap(c); caxis([0 255]);

figure()
image(dat(:,:,3)); title('blue channel');
c = zeros(256,3);            % setup a color axis with blue intensities
c(:,3) = 0:1/255:1;
colormap(c); caxis([0 255]);


figure();
image(blue); title('blue channel, down-sampled');
c = zeros(256,3);
c(:,3) = 0:1/255:1;
colormap(c); caxis([0 255]);


% reconstruct a complete image from reduced blue data
% interpolate linearly

[hes,wis] = size(blue);
dat(:,:,3) = interp2([1:width/wis:width],[1:height/hes:height]',blue,[1:width],[1:height]','linear');
figure();
image(dat); title('reconstructed image (linear interpolation)');

imwrite(dat,'test_image_blue64.tif','TIFF');