geomfunction.cpp

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/*
 *   libpal - Automated Placement of Labels Library
 *
 *   Copyright (C) 2008 Maxence Laurent, MIS-TIC, HEIG-VD
 *                      University of Applied Sciences, Western Switzerland
 *                      http://www.hes-so.ch
 *
 *   Contact:
 *      maxence.laurent <at> heig-vd <dot> ch
 *    or
 *      eric.taillard <at> heig-vd <dot> ch
 *
 * This file is part of libpal.
 *
 * libpal 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 3 of the License, or
 * (at your option) any later version.
 *
 * libpal 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 libpal.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include "geomfunction.h"
#include "feature.h"
#include "util.h"
#include "qgis.h"
#include "pal.h"
#include "qgsmessagelog.h"

using namespace pal;

void heapsort( int *sid, int *id, const double* const x, int N )
{
  unsigned int n = N, i = n / 2, parent, child;
  int tx;
  for ( ;; )
  {
    if ( i > 0 )
    {
      i--;
      tx = sid[i];
    }
    else
    {
      n--;
      if ( n == 0 ) return;
      tx = sid[n];
      sid[n] = sid[0];
    }
    parent = i;
    child = i * 2 + 1;
    while ( child < n )
    {
      if ( child + 1 < n  &&  x[id[sid[child + 1]]] > x[id[sid[child]]] )
      {
        child++;
      }
      if ( x[id[sid[child]]] > x[id[tx]] )
      {
        sid[parent] = sid[child];
        parent = child;
        child = parent * 2 + 1;
      }
      else
      {
        break;
      }
    }
    sid[parent] = tx;
  }
}


void heapsort2( int *x, double* heap, int N )
{
  unsigned int n = N, i = n / 2, parent, child;
  double t;
  int tx;
  for ( ;; )
  {
    if ( i > 0 )
    {
      i--;
      t = heap[i];
      tx = x[i];
    }
    else
    {
      n--;
      if ( n == 0 ) return;
      t = heap[n];
      tx = x[n];
      heap[n] = heap[0];
      x[n] = x[0];
    }
    parent = i;
    child = i * 2 + 1;
    while ( child < n )
    {
      if ( child + 1 < n  &&  heap[child + 1] > heap[child] )
      {
        child++;
      }
      if ( heap[child] > t )
      {
        heap[parent] = heap[child];
        x[parent] = x[child];
        parent = child;
        child = parent * 2 + 1;
      }
      else
      {
        break;
      }
    }
    heap[parent] = t;
    x[parent] = tx;
  }
}

bool GeomFunction::isSegIntersects( double x1, double y1, double x2, double y2,  // 1st segment
                                    double x3, double y3, double x4, double y4 )  // 2nd segment
{
  return ( cross_product( x1, y1, x2, y2, x3, y3 ) * cross_product( x1, y1, x2, y2, x4, y4 ) < 0
           && cross_product( x3, y3, x4, y4, x1, y1 ) * cross_product( x3, y3, x4, y4, x2, y2 ) < 0 );
}

bool GeomFunction::computeLineIntersection( double x1, double y1, double x2, double y2,  // 1st line (segment)
    double x3, double y3, double x4, double y4,  // 2nd line segment
    double *x, double *y )
{

  double a1, a2, b1, b2, c1, c2;
  double denom;

  a1 = y2 - y1;
  b1 = x1 - x2;
  c1 = x2 * y1 - x1 * y2;

  a2 = y4 - y3;
  b2 = x3 - x4;
  c2 = x4 * y3 - x3 * y4;

  denom = a1 * b2 - a2 * b1;
  if ( qgsDoubleNear( denom, 0.0 ) )
  {
    return false;
  }
  else
  {
    *x = ( b1 * c2 - b2 * c1 ) / denom;
    *y = ( a2 * c1 - a1 * c2 ) / denom;
  }

  return true;
}

int GeomFunction::convexHullId( int *id, const double* const x, const double* const y, int n, int *&cHull )
{
  int i;

  cHull = new int[n];
  for ( i = 0; i < n; i++ )
  {
    cHull[i] = i;
  }


  if ( n <= 3 ) return n;

  int* stack = new int[n];
  double* tan = new double [n];
  int ref;

  int second, top;
  double result;

  // find the lowest y value
  heapsort( cHull, id, y, n );

  // find the lowest x value from the lowest y
  ref = 1;
  while ( ref < n && qgsDoubleNear( y[id[cHull[ref]]], y[id[cHull[0]]] ) ) ref++;

  heapsort( cHull, id, x, ref );

  // the first point is now for sure in the hull as well as the ref one
  for ( i = ref; i < n; i++ )
  {
    if ( qgsDoubleNear( y[id[cHull[i]]], y[id[cHull[0]]] ) )
      tan[i] = FLT_MAX;
    else
      tan[i] = ( x[id[cHull[0]]] - x[id[cHull[i]]] ) / ( y[id[cHull[i]]] - y[id[cHull[0]]] );
  }

  if ( ref < n )
    heapsort2( cHull + ref, tan + ref, n - ref );

  // the second point is in too
  stack[0] = cHull[0];
  if ( ref == 1 )
  {
    stack[1] = cHull[1];
    ref++;
  }
  else
    stack[1] = cHull[ref-1];


  top = 1;
  second = 0;

  for ( i = ref; i < n; i++ )
  {
    result = cross_product( x[id[stack[second]]], y[id[stack[second]]],
                            x[id[stack[top]]], y[id[stack[top]]], x[id[cHull[i]]], y[id[cHull[i]]] );
    // Coolineaire !! garder le plus éloigné
    if ( qgsDoubleNear( result, 0.0 ) )
    {
      if ( dist_euc2d_sq( x[id[stack[second]]], y[id[stack[second]]], x[id[cHull[i]]], y[id[cHull[i]]] )
           >  dist_euc2d_sq( x[id[stack[second]]], y[id[stack[second]]], x[id[stack[top]]], y[id[stack[top]]] ) )
      {
        stack[top] = cHull[i];
      }
    }
    else if ( result > 0 ) //convexe
    {
      second++;
      top++;
      stack[top] = cHull[i];
    }
    else
    {
      while ( result < 0 && top > 1 )
      {
        second--;
        top--;
        result = cross_product( x[id[stack[second]]],
                                y[id[stack[second]]], x[id[stack[top]]],
                                y[id[stack[top]]], x[id[cHull[i]]], y[id[cHull[i]]] );
      }
      second++;
      top++;
      stack[top] = cHull[i];
    }
  }

  for ( i = 0; i <= top; i++ )
  {
    cHull[i] = stack[i];
  }

  delete[] stack;
  delete[] tan;

  return top + 1;
}

int GeomFunction::reorderPolygon( int nbPoints, double *x, double *y )
{
  int inc = 0;
  int *cHull;
  int i;

  int *pts = new int[nbPoints];
  for ( i = 0; i < nbPoints; i++ )
    pts[i] = i;

  ( void )convexHullId( pts, x, y, nbPoints, cHull );

  if ( pts[cHull[0]] < pts[cHull[1]] && pts[cHull[1]] < pts[cHull[2]] )
    inc = 1;
  else if ( pts[cHull[0]] > pts[cHull[1]] && pts[cHull[1]] > pts[cHull[2]] )
    inc = -1;
  else if ( pts[cHull[0]] > pts[cHull[1]] && pts[cHull[1]] < pts[cHull[2]] && pts[cHull[2]] < pts[cHull[0]] )
    inc = 1;
  else if ( pts[cHull[0]] > pts[cHull[1]] && pts[cHull[1]] < pts[cHull[2]] && pts[cHull[2]] > pts[cHull[0]] )
    inc = -1;
  else if ( pts[cHull[0]] < pts[cHull[1]] && pts[cHull[1]] > pts[cHull[2]] && pts[cHull[2]] > pts[cHull[0]] )
    inc = -1;
  else if ( pts[cHull[0]] < pts[cHull[1]] && pts[cHull[1]] > pts[cHull[2]] && pts[cHull[2]] < pts[cHull[0]] )
    inc = 1;
  else
  {
    // wrong cHull
    delete[] cHull;
    delete[] pts;
    return -1;
  }

  if ( inc == -1 ) // re-order points
  {
    double tmp;
    int j;
    for ( i = 0, j = nbPoints - 1; i <= j; i++, j-- )
    {
      tmp = x[i];
      x[i] = x[j];
      x[j] = tmp;

      tmp = y[i];
      y[i] = y[j];
      y[j] = tmp;
    }
  }

  delete[] cHull;
  delete[] pts;

  return 0;
}

bool GeomFunction::containsCandidate( const GEOSPreparedGeometry *geom, double x, double y, double width, double height, double alpha )
{
  if ( !geom )
    return false;

  GEOSContextHandle_t geosctxt = geosContext();
  GEOSCoordSequence *coord = GEOSCoordSeq_create_r( geosctxt, 5, 2 );

  GEOSCoordSeq_setX_r( geosctxt, coord, 0, x );
  GEOSCoordSeq_setY_r( geosctxt, coord, 0, y );
  if ( !qgsDoubleNear( alpha, 0.0 ) )
  {
    double beta = alpha + ( M_PI / 2 );
    double dx1 = cos( alpha ) * width;
    double dy1 = sin( alpha ) * width;
    double dx2 = cos( beta ) * height;
    double dy2 = sin( beta ) * height;
    GEOSCoordSeq_setX_r( geosctxt, coord, 1, x  + dx1 );
    GEOSCoordSeq_setY_r( geosctxt, coord, 1, y + dy1 );
    GEOSCoordSeq_setX_r( geosctxt, coord, 2, x + dx1 + dx2 );
    GEOSCoordSeq_setY_r( geosctxt, coord, 2, y + dy1 + dy2 );
    GEOSCoordSeq_setX_r( geosctxt, coord, 3, x + dx2 );
    GEOSCoordSeq_setY_r( geosctxt, coord, 3, y + dy2 );
  }
  else
  {
    GEOSCoordSeq_setX_r( geosctxt, coord, 1, x + width );
    GEOSCoordSeq_setY_r( geosctxt, coord, 1, y );
    GEOSCoordSeq_setX_r( geosctxt, coord, 2, x + width );
    GEOSCoordSeq_setY_r( geosctxt, coord, 2, y + height );
    GEOSCoordSeq_setX_r( geosctxt, coord, 3, x );
    GEOSCoordSeq_setY_r( geosctxt, coord, 3, y + height );
  }
  //close ring
  GEOSCoordSeq_setX_r( geosctxt, coord, 4, x );
  GEOSCoordSeq_setY_r( geosctxt, coord, 4, y );

  try
  {
    GEOSGeometry* bboxGeos = GEOSGeom_createLinearRing_r( geosctxt, coord );
    bool result = ( GEOSPreparedContainsProperly_r( geosctxt, geom, bboxGeos ) == 1 );
    GEOSGeom_destroy_r( geosctxt, bboxGeos );
    return result;
  }
  catch ( GEOSException &e )
  {
    QgsMessageLog::logMessage( QObject::tr( "Exception: %1" ).arg( e.what() ), QObject::tr( "GEOS" ) );
    return false;
  }
}

void GeomFunction::findLineCircleIntersection( double cx, double cy, double radius,
    double x1, double y1, double x2, double y2,
    double& xRes, double& yRes )
{
  double dx = x2 - x1;
  double dy = y2 - y1;

  double A = dx * dx + dy * dy;
  double B = 2 * ( dx * ( x1 - cx ) + dy * ( y1 - cy ) );
  double C = ( x1 - cx ) * ( x1 - cx ) + ( y1 - cy ) * ( y1 - cy ) - radius * radius;

  double det = B * B - 4 * A * C;
  if ( A <= 0.0000001 || det < 0 )
    // Should never happen, No real solutions.
    return;

  if ( qgsDoubleNear( det, 0.0 ) )
  {
    // Could potentially happen.... One solution.
    double t = -B / ( 2 * A );
    xRes = x1 + t * dx;
    yRes = y1 + t * dy;
  }
  else
  {
    // Two solutions.
    // Always use the 1st one
    // We only really have one solution here, as we know the line segment will start in the circle and end outside
    double t = ( -B + sqrt( det ) ) / ( 2 * A );
    xRes = x1 + t * dx;
    yRes = y1 + t * dy;
  }
}