How do I find the white pixel in the row/column

I can find the centroid of an white pixel image. I want to find the first/last white pixel in the row/column to calculate the distance of x and y.

Answer 1

[Vilém Frynta]

Hope this answers your question.

img = imread("pic1.jpg");   % loading your picture
img = rgb2gray(img);        % convert to black-and-white pic
row = 450;                  % choosing random row

idx = find(img(row,:)==0);  % position of all white pixels in row 450
diff = idx(1) - idx(end)    % difference of first and last pixel in row 450

diff = -598

This should work fine. I noticed your white == 0 and black == 255.

Also, this is for chosen row. If you change this a bit, you can get it for any column.