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Image processing

Laboratory 5 (ad)

Exercise 1

Try to analyse the histogram of the image mikolaj.jpg. The local maximum in this diagram results
from pixels of background. Choose the threshold below and above this maximum and compare the
results with the effect of Otsu algorithm.

Example 1
Binarization with 2 thresholds:

L = imread(

'portret.jpg'

);

imshow(zeros(600,800));

subplot(1,2,1),imshow(L);

subplot(1,2,2),imhist(L);

prompt = {

‘Choose the threshold value:’

,

’Choose the tolerance:’

};

odp = inputdlg(prompt);

prog = str2num(odp{1});

tol = str2num(odp{2});

L2 = (L<(prog+tol))&(L>(prog-tol));

figure;

imshow(L2);

Exercise 2

Modify the example above this way, that the user could click on the pixel of image and choose the
threshold (the value of threshold is equal the value of this pixel), and the tolerance should be
chosen in the dialog window.

Example 2
Animation of binarization::

L = imread(

'portret.jpg'

);

for

i=1:256

imshow(L>i);

pause(0.01);

end

;