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Re: Fwd: Phansalkar local thresholding

Posted by Gabriel Landini on Apr 23, 2014; 2:30pm
URL: http://imagej.273.s1.nabble.com/Fwd-Phansalkar-local-thresholding-tp5007401p5007402.html

On Wednesday 23 Apr 2014 08:33:53 you wrote:
> Can someone please point me at any published descriptions of the method,
> testing, or use of the “Phansalkar” method of local thresholding?  I see
> one reference in the ImageJ docs; I’m looking for more.

From the Auto Local Threshold info:
http://www.mecourse.com/landinig/software/autothreshold/autothreshold.html

Phansalkar
This is a modification of Sauvola's thresholding method to deal with low
contrast images.

1. Phansalskar N. et al. Adaptive local thresholding for detection of nuclei
in diversity stained cytology images. International Conference on
Communications and Signal Processing (ICCSP), 2011, 218-220.

In this method, the threshold t is computed as:

t = mean * (1 + p * exp(-q * mean) + k * ((stdev / r) - 1))

where mean and stdev are the local mean and standard deviation respectively.
Phansalkar recommends k = 0.25, r = 0.5, p = 2 and q = 10. In this plugin, k
and r are the parameters 1 and 2 respectively, but the values of p and q are
fixed.
Parameter 1: is the k value. The default value is 0.25. Any other number than
0 will change its value.
Parameter 2: is the r value. The default value is 0.5. This value is different
from Sauvola's because it uses the normalised intensity of the image. Any
other number than 0 will change its value
Implemented from Phansalkar's paper description, although this version uses a
circular rather than rectangular local window.

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