DIPlib Documentation - ©1995-2009 Quantitative Imaging Group, Delft University of Technology.

FeatureAnisotropy2D

Measure the anisotropy in a labeled region

SYNOPSIS

#include "dip_measurement.h"

dip_Error dip_FeatureAnisotropy2DID ( dip_int * )

FUNCTION

dip_FeatureAnisotropy2DID returns the ID value of this measurement function, that is registered by Initialise.

The grey value input image should contain an orienation field. For each labeled region, a tensor is constructed at each of the region's pixels. This tensor is as follow:

  cos^2(phi)         cos(phi)sin(phi)
[                                     ]
  cos(phi)sin(phi)   sin^2(phi)

The next step is to compute a new tensor, each element computed by averaging the corresponding elements of all the individual tensors. This average tensor represents the orientation information of the region as a whole. Eigenvalue analysis of this tensor yields two eigenvalues, the largest l0, the smallest l1. The anisotropy measure is: ( l0 - l1 ) / ( l0 + l1 ) which is zero for a fully isotropic regions (i.e. one where there is no prefered orientation), and one for a fully anisotropic region (i.e. when there is a single orientation).

SEE ALSO

Measure, FeatureSize, FeatureCenter, FeatureGravity, FeatureMean, FeatureSum, FeatureStdDev, FeatureMaximum, FeatureMinimum, FeatureMaxVal, FeatureMinVal, FeaturePerimeter, FeatureSurfaceArea, FeatureFeret, FeatureMass, FeatureInertia, StructureTensor2D

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