directionalfilter.c File Reference

directional filter for curvilinear feature extraction More...

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Detailed Description

directional filter for curvilinear feature extraction

Usage: directionalfilter.c in.pgm width length ndir out.pgm

Description: Let F be the original image from in.pgm . This operator computes the supremum of the convolutions of F by a series of kernels K0, ... Kn where n = ndir - 1, which are defined by, for each (x,y) and each i in [0...n]:

sigma = 1 / (2*width*width);
lambda = 1 / (2*length*length);
theta = i * PI / n;
xr = cos(theta) * x - sin(theta) * y;
yr = sin(theta) * x + cos(theta) * y;
Ki(x,y) = exp(-lambda*yr*yr) *
          (4*sigma*sigma*xr*xr - 2*sigma) * 
          exp(-sigma*xr*xr) 

Types supported: byte 2d, int32_t 2d, float 2d

Category: signal

Author:

Michel Couprie 2003