Detecting complex circular object in 2D images!!!!!!!

Hi, I have few images, 2D images taken by DSLR camera. The images are so complex for me as I am a beginner. The circular object is small and the poor background contrast. I want to detect almost circular or ellipse object in those image. How do I detect that object in MATLAB? There are few circular objects there to detect. The circular object quite small and some of it is partially hidden by other object. (Detecting apple fruit from tree)

This is the link for real image: http://www.flickr.com/photos/64698236@N03/5891874966/in/photostream/

Here is my testing image(this 1 might be easier): http://www.flickr.com/photos/64698236@N03/5892060924/in/photostream/

I already tried Detecting Circles<http://blogs.mathworks.com/pick/2008/05/23/detecting-circles-in-an-image/> in an Image but the results seem not accurate or does not works well for that image. I did change the radius for the circle. Do I miss any steps? I also tried other commands such as blobs demo, Hough_transform for circle detection.

This is the result image for circle detection; http://www.flickr.com/photos/64698236@N03/5931398663/in/photostream

Someone please help me.Thank you in advance.

Answer 1

[Sean de Wolski]

I would recommend trying to better segment the image before applying any circle detection algorithms.

Perhaps a standard deviation filter since the fruit appear to be smoother that their surroundings

doc stdfilt

[Fathin]

Thank you for your comment,

what do you mean by standard deviation filter? Is it Gaussian Filter?

[Sean de Wolski]

No. It measures the standard deviation of every neighborhood of a certain size in an image. Things with low standard deviation are more homogeneous. In your image, the fruit are pretty homogeneous.