how to find centroid of an object in an image???

Started by DXT_77 May 23, 2003
hi every body,

i have an image which has a picture of a ball in it
and i want to find the centroid of that ball
so when i display it on a 2dplot i know the exact pixel coord
and then i can find it's real coord.
the problem is i don't know how how to find or the formula for
centroid of an object?

thanks for any help,


Are you working with binary images. If so, then the following code will help you find the centroid of the image:
% read the image
i = imread('ball.bmp');
% convert to double
i = double(i);
% invert the image so that we can label the image
% the invert function is not given in the DIP toolbox
% i am attaching it with this email
i = invert(i);
% apply 8-connected algo
[labels,count] = bwlabel(i,8);
% calculate features. For more type help imfeature
features = imfeature(labels,'Centroid');
i = 1;
while i <= count
        % display centroid of all the subimages in the image
       i = i + 1;
Hope this helps.
Good luck

Zahra Atiq Shah

It's Samaritans' Week. Help Samaritans help others.
Call 08709 000032 to give or donate online now at

Attachment (not stored)
Type: application/octet-stream