dualtrees (version 0.1.5)

dt2cen: centre of the DT-spectrum

Description

calculate the centre of mass of the local spectra in hexagonal geometry

Usage

dt2cen(dt, mask = NULL)

Value

a nx x ny x 3 array where the third dimension denotes degree of anisotropy, angle and central scale, respectively.

Arguments

dt

a J x nx x ny x 6 array of spectral energies, the output of fld2dt

mask

a nx x ny array of logical values

Details

Each of the J x 6 spectral values is assigned a coordinate in 3D space with x(d,j)=cos(60*(d-1)), y(d,j)=sin(60*(d-1)), z(d,j)=j, where j denotes the scale and d the direction. Then the centre of mass in this space is calculated, the spectral values being the masses at each vertex. The x- and y-cooridnate are then transformed into a radius rho=sqrt(x^2+y^2) and an angle phi=15+0.5*atan2(y,x). rho measures the degree of anisotropy at each pixel, phi the orientation of edges in the image, and the third coordinate, z, the central scale. If a mask is provided, values where mask==TRUE are set to NA.

Examples

dt <- fld2dt(blossom)
ce <- dt2cen(dt)
image( ce[,,3], col=gray.colors(32, 0, 1) )