centroid of a image

I dont undertand how we can find a centroid of a image. I want to know x and y of the place where the centroid is set. Also I want to plot the point in the image.

thank you

Answer 1

[Image Analyst]

The centroid will be in the center of the image. The "weighted" centroid, or center of mass, will depend on the gray levels in the image. Both can be gotten from regionprops() as my Image Segmentation Tutorial shows: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862&sort=downloads_desc

labeledImage = bwlabel(true(size(grayImage)));
props = regionprops(labeledImage, grayImage, 'Centroid', 'WeightedCentroid');

props is a structure with fields for both of those measurements.

[Yuri Minami]

thank you

Answer 2

[Walter Roberson]

The centroid of an image is always at the exact center of the image. Every pixel has the same "weight" as every other pixel for the purposes of determining centroids.

If you want bright pixels to be more important than dark pixels, then possibly you are interested in centre of mass rather than centroid.

If you want to find the centroid of a portion of the image, then create an ROI (a binary mask) and use regionprops() to calculate its centroid.

[Yuri Minami]

Thank you. yes I want to know the center of mass of a blighter area.