Polygon Functions for Octave & MATLAB
=====================================

A mex interface to the Clipper library by Angus Johnson
http://www.angusj.com/delphi/clipper.php, and mex
functions for fast calculation of polygon orientation and
for testing if a point is inside a polygon.


Polygon clipping:
-----------------

       [pc,hc] = polybool(pa, pb, 'op', ha, hb, ug);
       
where 'op' can be 'and' (intersection), 'or' (union), 'notb' or 'diff'
(difference), and 'xor'. pa, pb, and pc are cell arrays with nx2
matrices containing polygon vertices (one vertex per row). ha, hb, hc
are logical arrays with hole flags. If ha(k) > 0, then pa{k} is an
interior polygon belonging to a polygon with one or more holes. The 
clipping operation is performed on an integer grid. The polygon data
are multiplied with the scale factor 'ug' prior to the clipping
operation and the resulting polygons are scaled by 1/ug.


Polygon orientation:
--------------------

       cw = iscw(pa);
       
Make polygons oriented clockwise (cw) or counter clockwise (ccw):

       P = polycw(pa);

where P and pa are cell arrays of polygons.


Check if points are inside a polygon:
-------------------------------------

       inp = isinpolygon(polygon, xy);

where 'polygon' is a n x 2 array of polygon vertices and 'xy' an n x 2 array
of points. 'inp' is a logical arrray.


Polygon area
------------

       A = polyarea(pa);

where 'pa' is a cell array of polygons and 'A' is a vector with polygon areas.


Polygon centroid
----------------

       C = polycentr(pa);

where 'pa' is a cell array of polygons and 'C' is an nx2 array with centroids,
one per row for each input polygon. Call twice to calculate the combined 
centroid of multiple polygons.


Compilation:
------------
The mex functions must be compiled before they can used.

On MATLAB or on Octave/Windows type the command
   
   makemex

at the MATLAB prompt (the polybool directory must be the current 
directory). For Octave on Linux compile the mex functions by 
running 

   ./makemex-octave

at a shell prompt.

------------------------
Ulf GRIESMANN, 2016
ulf.griesmann@nist.gov
ulfgri@gmail.com