Re: Feret's dimeter
Posted by
Gabriel Landini on
Jan 11, 2015; 11:13am
URL: http://imagej.273.s1.nabble.com/Feret-s-dimeter-tp5011144p5011173.html
On Sunday 11 Jan 2015 11:54:17 Michael Schmid wrote:
> Hi Slobodan,
>
> yes, if you create a circle (oval selection) with a diameter of 3 pixels
> it and fill it, you will get a square of 3x3 pixels. This square has a
> minFeret of 3 (if you measure it with calipers touching two sides) and a
> maxFeret of 3*sqrt(2) = 4.24 pixels (calipers measuring the diagonal).
>
> For larger circles (diameter >= 4), filling does not result in a square
> any more, but the maxFeret will be still too large.
>
> In any case, for calculating Feret diameters and areas, pixels are assumed
> to be small squares with a side length of 1, not single points.
The Particles8 plugin uses an different concept of the "area" of a region (it
uses Freeman chaincodes algorithm which I find more intuitive) and among other
things it computes the max Feret diameter based on the boundary of a region.
Since a single pixel here is considered a point, not a region, it has no
boundary and no inside area, so its max Feret diameter is 0.
It does not compute the minimum Feret though.
Here it is for plain IJ (in the Morphology zip)
http://www.mecourse.com/landinig/software/software.htmlor add the Morphology repository for Fiji.
Cheers
Gabriel
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