[SciPy-user] circumference in raster image

Zachary Pincus zachary.pincus@yale....
Wed Jul 8 10:47:32 CDT 2009


>>> Attached is find_contours, an extension module that finds all  
>>> contours
>>> in a 2D array at a specified iso-value. The contour position is  
>>> linearly
>>> interpolated between pixels. Let me know if you have any  
>>> questions, etc.
>>> (Looking over the code, I'm surprised how well I documented and
>>> commented it... lucky break for anyone who wants to use or modify  
>>> it, I
>>> guess.) It's GPL because it comes from a larger GPL'd project of  
>>> mine,
>>> but just ask me and I'll send it under a different license.
>>
>> Thank you very much, I will try your code. This is the way I  
>> thought I
>> might try (interpolating by a smooth function/polynomial), so it's  
>> cool
>> I do not have to dive into it :-)
>
> ok, I have tried find_contours() - it seems very suitable for my  
> purposes!

Note of course that if the image starts out as binary, the exact same  
problems that Gary described will apply: the contour segments will all  
point in one of eight directions...

If the image originates as non-binary on the other hand, and instead  
of thresholding at value X, you find the iso-contours at value X, you  
might be able to get better values.

Probably worth doing some ground-truth testing with mockup images. I'd  
be interested in the results.

Zach


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