How to find the accurate position of first white pixel in an image?

I had done several coding to find the first white pixel in an image:

%Mark horizontal pixel
[row1, column1] = find(thinImg, 1, 'last');
hold on;
plot(column1, row1, 'yX', 'MarkerSize', 15);

%Mark vertical pixel
[row2, column2] = find(thinImg, 1, 'first');
hold on;
plot(row2, column2, 'yX', 'MarkerSize', 15);

Here is the result of the processed image http://postimg.org/image/er5r7k4x9/.. There is no problem to find the first white pixel in horizontal axis.. However,problem occurred when i tried to find the first white pixel in vertical axis (*marked by red circle).. Any suggestion on how to solve this problem?

Answer 1

[Jan]

If finding the first pixel in horizontal direction works well, you can transpose the image:

thinImgT = transpose(thinImg)

and than use the detector for the horizontal direction again.

[Narges M]

yes this works, or simply do this: [row1, column1] = find (thinImg ' , 1, 'first');

[Dhandapani.S]

ok what is the way to find top-left, top-right, bottom-left and bottom-right coordinate in a binary image?

[Image Analyst]

Did you not see the answer to this when you asked it as a separate question? Here it is: http://www.mathworks.com/matlabcentral/answers/169071-how-to-find-the-corners-of-an-irregular-binary-shape#answer_164134