Finding X and Y coordinates of a single white blob on a black background

I have a series of images which I need to find the x,y coordinates for a single white blob on black background. I would like coordinates to be taken from the center of the image. Thank you.

Answer 1

[Image Analyst]

This is done by my BlobsDemo program. http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862.

The blobs are the coins from the standard MATLAB demo image. It finds the centroids of all of them. You just need to subtract the number of rows and columns divided by 2 to get the coordinates referenced to a new coordinate system where the origin is in the middle of the picture.

[David Bridges]

Thank you, this works great!

[David Bridges]

Do you know how I can loop the detector for multiple .jpg files so that I can get the centroids for multiple files in one go? Really appreciate your help!

[Image Analyst]

Sure! See code examples for that in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

[David Bridges]

Thanks, I have tried that but I cannot make it fit with your existing code. If you wouldn't mind a quick look, I have attached something that is looping already, but it only prints the centroids of the last jpg file in the folder. Files are virus-checked etc. Much appreciated!

[Image Analyst]

You have a loop that says

for j=1

so of course it does only 1 image.

[David Bridges]

Finally figured it out, thanks for your help