How can I store pixel position in two different array ?

Hi , I want to store the position of the pixel where Intensity value is 255. There are two arrays A and B for rows and columns respectively. I am using the below code, although code is error free but not returning expected result.

I=imread('img.jpg');
A=[];
B=[];
k=0;
for i=1:80
       for j=1:120
         if I(i, j)==255
           A(k)=i;
           B(k)=j;
         end
         k=k+1;
     end
end

Image dimension is 80*120. Thanx.....

[Mark]

Just a side note... it appears that you are indexing k regardless of whether your criteria (I(i,j)==255) or not. This may be why the result is not expected? You could always look to use

A=cat(1,A,i) B=cat(1,B,j)

[KaMu]

Why dont u use find, it is very infromative: http://www.mathworks.com/help/matlab/ref/find.html

Answer 1

[Mark]

This should help...

      I=imread('img.jpg'); %Assuming this is a gray-scale image
      idx=find(I==255);
      [B,A]=ind2sub(size(I),idx);

      figure; imshow(I); hold on
      plot(A,B,'r.');
      hold off

[Rajesh Gothwal]

thanx... Eexpected result obtained

Answer 2

[Image Analyst]

You need to have k=k+1 INSIDE your "if", not outside it. That's the cause of your problem.

Of course you can just get rows and columns directly from find() without using linear indexes and ind2sub, or a nested "for" loop:

[rows, columns] = find(I == 255);

rows is what you call A, and columns is what you call B. I encourage you to use more descriptive variable names, like I did. Also, don't use I as a variable name - it looks too much like 1 or l. Use a descriptive name like grayImage or binaryImage or something.

[Rajesh Gothwal]

sounds great...