Posted by
Robert Dougherty on
Jul 06, 2020; 3:30pm
URL: http://imagej.273.s1.nabble.com/curvature-along-the-outline-of-a-thresholded-object-tp5023589p5023628.html
Herbie,I have a post hoc processing step in my code. I smooth the reciprocal of the radius of curvature. I actually use a weighted power mean for that, as it seemed like the right thing to do, without much evidence.Bob
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On Monday, July 6, 2020, 1:20 AM, Herbie <
[hidden email]> wrote:
Good day Thomas,
I'm far from sure what you mean by "sensitivity" and "noise" in the context
of curvature.
Obviously, the main problem with general curvature measurements from
spatially discrete images, is the discreteness of the signal. Consequently
and in order to increase accuracy and precision (not the same), we need
reasonable interpolation and I see no chance that this can be performed post
hoc.
With ImageJ I'd use "Interpolation" fom the "Selection"-menu with a
reasonable interval setting. This may provide sufficiently small and perhaps
even equal intervals for the computation of the required difference
quotients. Not perfectly sure yet, but I'd then favour the curvature
computation from polar coordinates as formulated here:
<
https://en.wikipedia.org/wiki/Curvature#Polar_coordinates>
I think you could achieve this yourself by writing a little macro.
Regards
Herbie
::::::::::::::::::::::::::::::::::::
Dear Bob,
My reply is late because I had computer problems. The result of the plugin
looks nice. In order to use it I would need two features
1) A parameter to tune the sensitivity. Right now it is not sensitive
enough for my purpose. I am aware that an increase in sensitivity would
make the result more noisy. But as with the plugin of Thomas I would do the
smoothing afterwards.
2) A list of the curvature values along the circumference. Just looking at
the nice result is not enough in my case. I have to extract numbers from
this list.
I am content with the plugin of Thomas. But as we say in German: the better
is the enemy of the good.
Best regards, Thomas
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