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What is the simplest possible way to calculate the coordinates of the center and the radius of the circle on the image (for example BMP and I'm interested in image of the Sun included below)?

Image

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    $\begingroup$ Select from en.wikipedia.org/wiki/Outline_of_object_recognition. I recommend read en.wikipedia.org/wiki/Hough_transform first. $\endgroup$ – Apiwat Chantawibul Jan 8 '17 at 23:21
  • $\begingroup$ The implementation part is off-topic here, but it would be two steps procedure: (scale detect edges, run circular Hough Transform. Both are easy to implement and are available in e.g. OpenCV. If you are interested in algorithm please edit your question, otherwise it might be on-topic at Stack Overflow or graphics. $\endgroup$ – Evil Jan 8 '17 at 23:26
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    $\begingroup$ The simplest possible way is to manually draw a circle over the perimeter of the sun, in an image editing/paint program, and look at the pixel coordinates of that image. Are you looking for an automated algorithm? Will the image always look just like the one you've shown or will there be other types of images? What research have you done, and what techniques have you already considered? $\endgroup$ – D.W. Jan 9 '17 at 2:49
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If you want to automate the process I would use Hough Circle Transform. It is an algorithm used to detect circles in an image. This Wiki article will describe Hough Transform better than I can.

You can manually find the center of a circle using these methods.

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