Measuring angles using Directionality plugin


I started using the Directionality plugin in Fiji (ImageJ) in order to measure the angular position of the hair that is rotating on a droplet.

Here is the orientation map of an example image given by this plugin.


The inferred direction is correct, however the data ‘Direction’ was not incorrect. So I plotted the raw data from the table and I could see the correct peak (in the examle figure between 50 and 60 degrees).

I would like to know how to obtain the correct data given by this peak or what I should do.

I would really appreciate any help.

Thank you very much!


I suspect the peak at 0º comes classically with a pb with the FFT.
I am not sure Directionality is the right tool, but whatever works right?

Would you be ok to share a raw image so that I can fiddle with it?

Herbie kindly wrote me the following, and it might be interesting to you:

"Salut Jean-Yves,

In the very case it is a good idea to change the color system. One may
use either HSB or CMYK. Attached please find the result obtained from
the Saturation-channel by using the “Global Orientation Salience”-option
of the ImageJ-plugin “Orientations_”.
(Directionality should lead to a comparable result.)

According to the attached, the most salient orientation is 34deg
counterclockwise from the horizontal.
The result obtained with the ImageJ-plugin “Angular Deviation” is 34.11deg.

You may report everything to the Forum.

Best regards"

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I am sending the raw image.


Thank you for the help. I think that you set me to the right path to solve my problem.