| Re: Image analysis and ring identification [message #30462 is a reply to message #30352] |
Mon, 22 April 2002 11:56  |
Jonathan Joseph
Messages: 69
Registered: September 1998
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Member |
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How large are these rings that you are talking about?
I have some IDL code that will fit an ellipse to a group of points.
It requires at least 6 input points. The center is readily available.
I hesitate to just post it because it's not my own code.
I found the code on the web written in java and took the bits that
were relevant to me and converted them to IDL. It's publicly
available code - but very few comments, no warranty, etc. I
believe the original author's name is Maurizio Pilu (see
http://vision.dai.ed.ac.uk/maurizp/ElliFitDemo/ for a demo)
If it looks useful, I can post my IDL code.
-Jonathan
Rachel Pepper wrote:
>
> Sorry to be so confusing! I want the center of the circle (ie the bright ring)
> and the bright spots are messing up the centroid-based method (James is right).
>
> Rachel
>
> David Fanning wrote:
>
>> James Kuyper (kuyper@gscmail.gsfc.nasa.gov) writes:
>>
>>> Yes, but I didn't get the impression that he wants to find the bright
>>> spot. He asked how to determine the center of the circle, and complained
>>> about the fact that the bright spot would mess up the centroid-based
>>> method of calculating the center, because the bright spot was off-center.
>>
>> Isn't language odd? I thought she asked how to find the
>> center of the ring, but then realized she wasn't interested
>> in the center, but in the bright spot, which wasn't necessarily
>> in the center. I think she might be able to have her cake
>> and eat it too, depending upon the values she uses to
>> calculate the centroid. In fact, she might even learn
>> something fascinating about her rings by measuringg how
>> the centroid changes between the two different calculations.
>>
>> But, hang on a minute! We don't have to be Aristotle and
>> his friends arguing endlessly about how many teeth a
>> horse has, we can ask the source. Rachel, what in the
>> world are you asking about?
>>
>> Cheers,
>>
>> David
>> --
>> David W. Fanning, Ph.D.
>> Fanning Software Consulting
>> Phone: 970-221-0438, E-mail: david@dfanning.com
>> Coyote's Guide to IDL Programming: http://www.dfanning.com/
>> Toll-Free IDL Book Orders: 1-888-461-0155
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