Hi Andrew,
it's difficult to give any advice without seeing a sample image. Can you
attach one (if a small file) or upload one on a web server?
If some segmentation method (e.g. preprocessing and thresholding) can get
the circle, you may fill the circle, and fit an ellipse (Analyze>Set
Measurements, select 'Fit Ellipse, then Analyze>Measure). With the
coordinates of the circle, you can create a circular selection (if the
previous selection is not good enough).
Then use e.g. Image>Adjust>Color Threshold to select what you consider
green pixels, get the circle selection, and create appropriate macro code
with Plugins>Macros>Record.
Then use e.g. the getRawStatistics macro command.
If segmentation does not work to recognize the circle, have a look at the
various Hough transform plugins, whether you find a suitable one for
detecting your circles.
Michael
___________________________________________________________________
On Fri, May 22, 2015 23:51, Andrew Sanchez wrote:
> I am trying to automate the task of manually selecting a circular area.
>
> The circle I need to select is very apparent and has fairly thick white
> borders. I am wondering if ImageJ can recognize the circle.
>
> Unfortunately, the size and location of the circle varies slightly from
> image to image.
>
> Is it possible for ImageJ to recognize a large circle in my images, and to
> select and crop that area?
>
> The ultimate goal is to then count the number of green pixels within the
> circle.
>
> Thank you,
> Andrew Sanchez
> Lab Assistant
> Center for Ecosystem Science
> Northern Arizona University
>
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