Posted by
Robert Smith on
Jul 10, 2017; 10:38pm
URL: http://imagej.273.s1.nabble.com/Calculating-grazing-area-tp5019047p5019051.html
Thresholding is based on above and below pixel values, you may have to threshold twice (or more, once above the required limit and once below it.) Yes it is sometimes difficult to cover an irregular area.
Hope this works, it did for me.
Bob
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From: PEARSON Matthew<mailto:
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Sent: Monday, July 10, 2017 11:05 AM
To:
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Subject: Re: Calculating grazing area
Hi Josh,
Well I didn't think i'd be discussing snails today! :) Sometimes you can use morphological filters to pre-process the image which I find sometimes improves the accuracy of thresholding, see the Process menu. I guess you could also try manually drawing around the grazing area using a selection tool and subtract this from the total image area-could be laborious but hard to know without an image as herbie says. For example i'm assuming this is a black and white image from a microscope using transmitted brightfield or some kind of episcopic illumination?
Thanks,
Matt
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Matt Pearson
Microscopy Facility
MRC Human Genetics Unit
Institute of Genetics and Molecular Medicine (IGMM)
University of Edinburgh
Crewe Road
EH4 2XU
On 10 Jul 2017, at 14:53, joshcurran <
[hidden email]<mailto:
[hidden email]>> wrote:
Hi there,
I'm brand new to ImageJ and am just trying to get to grips with it. I've
been playing around with it all day.
I'd like to calculate the percentage area grazed by snails across an algal
biofilm. I understand that I can threshold the image, but the biofilm isn't
amazingly consistent with colour across the dish. When I was practicing and
testing it out earlier on when thresholding it wasn't really covering the
parts I wanted it to. Any advice or tips? Or is there another way that
grazing area could be measure?
Many thanks,
Josh
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