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perimeter

PURPOSE ^

PERIMETER estimate perimeter of a structure

SYNOPSIS ^

function perim = perimeter(img, varargin)

DESCRIPTION ^

PERIMETER estimate perimeter of a structure

   p = perimeter(img);
   Compute estimation of perimeter of structure in image IMG, using a
   discrete version of Crofton formula in 4 directions (horizontal,
   verticval, and 2 diagonals) of image.
   
   p = perimeter(img, method);
   Specifies the method to employ :
   - 'local4' : create polygon around the structure, using 4 connectivity,   
   and compute perimeter of piolygon. This usually gives a great
   overestimation of the perimeter.
   - 'local8' : create polygon using 8 connectivity, giving a smaller
   overestimation.
   - 'crofton' (default) : count intersections with discete lines in 4
   directions (horizontal, vertical, and 2 diagonals), and uses Crofton
   formula to estimate perimeter.
   - 'crofton2' : uses only 2 orthogoanl directions to count
   intersections. Works better for spheres, but not so good for others
   figures.

   TODO: there is a small biais for some configuration using 'crofton'
   This concerne only config with type [1 0;0 1] or [0 1;1 0] : the
   contribution of the diagonal line is not counted, leading to
   underestimation of perimeter of thin structures.

   
   ---------

   author : David Legland 
   INRA - TPV URPOI - BIA IMASTE
   created the 03/04/2005

CROSS-REFERENCE INFORMATION ^

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