why aren't black pixels appearing where the imfreehand contour was drawn?

Consider this:

imag = imread ('pout.tif');
figure, imshow (imag);
h = imfreehand (gca, 'Closed', false);

position = int16(getPosition(h));

for i=1:size(position,1)

      imag([position(i,1),position(i,2)])=0; 
      %attempts to mark the positions on the contour as black 

end

figure, imshow(imag); %%no changes shown, why?

What I'm missing here?

Answer 1

[Image Analyst]

You used brackets around the row and column, which ruined it. Plus you reversed the row and columns. x is column, not row! And y is row, not column! Try it this way:

for i=1:size(position,1)  
  imag(position(i,2),position(i,1))=0;
  %attempts to mark the positions on the contour as black  
end