What are the algorithms to perform HDRI in an image ?

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Refer: http://en.wikipedia.org/wiki/High_dynamic_range_imaging In context of: http://www.omron-ap.co.in/application_solutions/category_details.asp?app_id=E533

I want to detect outer and inner diameter of several springs. For which I think I need the mentioned thing. And I think its not histogramEquilization().