% downsample3.m

dat = imread('test_image.tif');
dat2 = dat(320,330:369,2);
clear dat;

subplot(3,3,4)
plot([1:40],dat2,'ko--','MarkerSize',6,'MarkerFaceColor','k')
title('original')
xlabel('x')
ylabel('green intensity')
axis([-2 42 0 255]);

h = length(dat2);

dat2 = double(dat2);

for lx=1:h/4,
   x = (lx-1)*4+1;
   mg = (dat2(x) + dat2(x+1) + dat2(x+2) + dat2(x+3))/4;
   dat3(lx) =mg
   dat4(x:x+3) = mg;
end;

dat3= uint8(dat3);
subplot(3,3,5);
plot([1:4:40],dat3,'ko--','MarkerSize',6,'MarkerFaceColor','k')
title('stored data');
xlabel('x')
ylabel('green intensity')
axis([-2 42 0 255]);


dat4 = interp1([1:4:40],double(dat3), [1:37], 'linear')
dat4 = uint8(dat4);
subplot(3,3,3);
plot([1:37],dat4,'ko--','MarkerSize',6,'MarkerFaceColor','k')
title('linear interpolation');
xlabel('x')
ylabel('green intensity')
axis([-2 42 0 255]);

dat5 = interp1([1:4:40],double(dat3), [1:37], 'spline')
dat5 = uint8(dat4);
subplot(3,3,9);
plot([1:37],dat5,'ko--','MarkerSize',6,'MarkerFaceColor','k')
title('spline interpolation');
xlabel('x')
ylabel('green intensity')
axis([-2 42 0 255]);