Re: particle analysis-Feret diameter

Hi all,

If my understanding of Feret diameter in ImageJ is correct, this is the 
*maximum* one, calculated at various angles. But how many angles are 
considered? I browse the source code rapidly, and found several 
getFeretsDiameter() functions (ij.gui.OvalRoi, PolygonRoi, Roi & 
ShapeRoi). In particular, in ShapeRoi, you also have a getMinFeret() 
function, but it is commented out. Apparently, shape is rotated every 
degree in these function?

Anyway, I join Mr Kachrimanis in a request for reporting also the 
*minimum* (and possibly the *mean*) Feret diameter. A lot of derived 
measurements can be done if you have those additional measurements. My 
plan for the future is to patch ImageJ to report those. This should not 
be too difficult... unfortunatelly, I am not a Java programmer and have 
little free time now. So, this is a pain for me, and I will not do it 
before one year, or so (I still hope to see it added in a future version 
of ImageJ).

Best,

Philippe Grosjean

P.S.: by the way, many thanks for adding 'Skew' and 'Kurt' in the 
particle analyzer in the latest version of ImageJ!

..............................................<°}))><........
 ) ) ) ) )
( ( ( ( (    Prof. Philippe Grosjean
 ) ) ) ) )
( ( ( ( (    Numerical Ecology of Aquatic Systems
 ) ) ) ) )   Mons-Hainaut University, Pentagone (3D08)
( ( ( ( (    Academie Universitaire Wallonie-Bruxelles
 ) ) ) ) )   8, av du Champ de Mars, 7000 Mons, Belgium
( ( ( ( (
 ) ) ) ) )   phone: + 32.65.37.34.97, fax: + 32.65.37.30.54
( ( ( ( (    email: Philippe.Grosjean@xxxxxxxxx
 ) ) ) ) )
( ( ( ( (    web:   http://www.umh.ac.be/~econum
 ) ) ) ) )          http://www.sciviews.org
( ( ( ( (
..............................................................

K. Kachrimanis wrote:
> Dear all,
>
> I have a question or rather a feature request related to the particle analysis, 
> which so far has limited functionality copared to commercial software packages 
> in regard to particle size and shape analysis. I have noticed that there is a 
> Feret diameter included in the module, but it is not clear at which orientation 
> is this Feret measured. Since Feret diameters depend on particle orientation, a 
> Feret at a single orientation is virtually useless, particularly when one has 
> to deal with elongated particles. Would it be possible to include more Ferets, 
> at different angles, and also add an automatic selection of maximum and minimum 
> Ferets? This would enable the calculation of the aspect ratio and other 
> relevant shape descriptors.
>
> Regards,
>
> K.Kachrimanis.