Automate circular ROI selection

Posted by Andrew Sanchez on Jun 05, 2015; 8:35pm
URL: http://imagej.273.s1.nabble.com/Automate-circular-ROI-selection-tp5013060.html

I am trying to automate the selection of a circular ROI.  I have been
exploring some suggested solutions like Hough transformation (
http://rsb.info.nih.gov/ij/plugins/hough-circles.html) and segmentation,
including the Trainable Weka Segmentation tool, but have not had any so
far, most likely due to my slow climb of the learning curve as a new user.

I am brand new to ImageJ, and am working my way through tutorials and
documentation for a solution.

Here is a sample image:
https://drive.google.com/file/d/0B208tul7KbkbX2RYLXhDLXJlVFE/view?usp=sharing

I need to select everything inside of the thick white circle, take the area
of the circle in pixels, and then count the number of green pixels.  Is
there  a way to do this without manually selecting the circle for every
image?

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Thank you,
Andrew Sanchez
Lab Assistant
Center for Ecosystem Science
Northern Arizona University

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