Center of mass in binary image

Hello, I have a binary image with one object. How can I calculate the center of this object, to mark it in my image and to write the coordinates in the corner of this image, like this: object: X, Y

I used this code to calculate the center of mass:

s = regionprops(bw, 'centroid');

centroids = cat(1, s.Centroid);

imshow('MY_IMAGE.jpg')

hold on

plot(centroids(:,1), centroids(:,2), 'b*')

hold off

but how can i plot this coordinates on my image in the left corner?

Thank you for help

Answer 1

[David Sanchez]

use text command:

your_string = strcat( num2str(centroids(:,1)),'-', num2str(centroids(:,2)));
text(10,10,your_string)

change the position by changing the "10,10" values

[Felix]

Thank you! How can I change the background and the color of the text?

[Image Analyst]

Look up Text properties in the help. You will see 'BackgroundColor' and 'Color':

text(x, y, yourString, 'Color', [1, ,5, .2], 'BackgroundColor', [.1, .3, .2]);

[Felix]

Thank you it's works, another question, how can i write in this way:

Object: X,Y(coordinates)

now it gives me only a coordinates and can i also write a coordinates without a numbers after '.'? only integers

[Image Analyst]

Use sprintf to create your string, and cast your numbers to integers or use %.0f:

textString = sprintf('Object: %d, %d (coordinates)', int32(X), int32(Y));
text(x,y,textString);

[Felix]

thnx

Answer 2

[Walter Roberson]

ndgrid() of 1:width and 1:height, do a logical indexing of those according to the binary image, calculate the mean() of what is left in each of the two coordinate matrices. Result will be centre of mass along each of the two coordinates.

Answer 3

[Mauldy Putra]

i want to ask, in your code there is bw i want to know what is bw stand for? cause i try use your code it's said "Undefined function or variable 'bw'."

thank you

[Walter Roberson]

bw is the binary image whose center of mass is to be found.