Question

I just scanned a sample image and I’m trying to detect the first pixel which has a value of “0” in the binary-image.
I used paint to write a text and when i used the following prog, it always catches the bottom most pixel.

    clear all;
    x=imread('textjay.png');
    y=im2bw(x);

    height=size(y,1); % row
    width=size(y,2);  % col

    valueoftheindex=0;

    pixel_value=0;

    for i=1:width
     for j=1:height
      pixel_value=y(j,i);
      if (pixel_value==0)
       valueofthewidth=i;
       valueofthehieght=j;
       break
      end
      end
     end

    valueofthewidth
    valueofthehieght

    imtool(y)

Answer 1

This depends a lot on what you consider to be “the first pixel”.
Assuming that you can live with the pixel order that MATLAB assigns you could use

idx = find(y == 0, 1, 'first')
[row_idx, col_idx] = ind2sub(size(y), idx)

For other measures of “firstness” you would have to either transpose the input matrix (the image), or resort to some more refined way of calculation.

And yes, the break will only break the inner loop, as dawe already pointed out.