zoneminder/src/zm_poly.cpp

//
// ZoneMinder Polygon Class Implementation, $Date$, $Revision$
// Copyright (C) 2001-2008 Philip Coombes
// 
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
// 

#include "zm_poly.h"

#include <cmath>

void Polygon::calcArea() {
  double float_area = 0.0L;
  for ( int i = 0, j = n_coords-1; i < n_coords; j = i++ ) {
    double trap_area = ((coords[i].X()-coords[j].X())*((coords[i].Y()+coords[j].Y())))/2.0L;
    float_area += trap_area;
    //printf( "%.2f (%.2f)\n", float_area, trap_area );
  }
  area = (int)round(fabs(float_area));
}

void Polygon::calcCentre() {
  if ( !area && n_coords )
    calcArea();
  double float_x = 0.0L, float_y = 0.0L;
  for ( int i = 0, j = n_coords-1; i < n_coords; j = i++ ) {
    float_x += ((coords[i].Y()-coords[j].Y())*((coords[i].X()*2)+(coords[i].X()*coords[j].X())+(coords[j].X()*2)));
    float_y += ((coords[j].X()-coords[i].X())*((coords[i].Y()*2)+(coords[i].Y()*coords[j].Y())+(coords[j].Y()*2)));
  }
  float_x /= (6*area);
  float_y /= (6*area);
  //printf( "%.2f,%.2f\n", float_x, float_y );
  centre = Coord( (int)round(float_x), (int)round(float_y) );
}

Polygon::Polygon(int p_n_coords, const Coord *p_coords) : n_coords( p_n_coords ) {
  coords = new Coord[n_coords];

  int min_x = -1;
  int max_x = -1;
  int min_y = -1;
  int max_y = -1;
  for ( int i = 0; i < n_coords; i++ ) {
    coords[i] = p_coords[i];
    if ( min_x == -1 || coords[i].X() < min_x )
      min_x = coords[i].X();
    if ( max_x == -1 || coords[i].X() > max_x )
      max_x = coords[i].X();
    if ( min_y == -1 || coords[i].Y() < min_y )
      min_y = coords[i].Y();
    if ( max_y == -1 || coords[i].Y() > max_y )
      max_y = coords[i].Y();
  }
  extent = Box( min_x, min_y, max_x, max_y );
  calcArea();
  calcCentre();
}

Polygon::Polygon( const Polygon &p_polygon ) :
  n_coords(p_polygon.n_coords),
  extent(p_polygon.extent),
  area(p_polygon.area),
  centre(p_polygon.centre)
{
  coords = new Coord[n_coords];
  for( int i = 0; i < n_coords; i++ ) {
    coords[i] = p_polygon.coords[i];
  }
}

Polygon &Polygon::operator=( const Polygon &p_polygon ) {
  if ( n_coords < p_polygon.n_coords ) {
    delete[] coords;
    coords = new Coord[p_polygon.n_coords];
  }
  n_coords = p_polygon.n_coords;
  for ( int i = 0; i < n_coords; i++ ) {
    coords[i] = p_polygon.coords[i];
  }
  extent = p_polygon.extent;
  area = p_polygon.area;
  centre = p_polygon.centre;
  return *this ;
}

bool Polygon::isInside( const Coord &coord ) const {
  bool inside = false;
  for ( int i = 0, j = n_coords-1; i < n_coords; j = i++ ) {
    if ( (((coords[i].Y() <= coord.Y()) && (coord.Y() < coords[j].Y()) )
    || ((coords[j].Y() <= coord.Y()) && (coord.Y() < coords[i].Y())))
    && (coord.X() < (coords[j].X() - coords[i].X()) * (coord.Y() - coords[i].Y()) / (coords[j].Y() - coords[i].Y()) + coords[i].X()))
    {
      inside = !inside;
    }
  }
  return inside;
}