C++ QgsVector::length方法代码示例

QgsVector calcMotion( const QgsPoint &a, const QgsPoint &b, const QgsPoint &c,
                      double lowerThreshold, double upperThreshold )
{
  QgsVector p = a - b;
  QgsVector q = c - b;

  if ( qgsDoubleNear( p.length(), 0.0 ) || qgsDoubleNear( q.length(), 0.0 ) )
    return QgsVector( 0, 0 );

  // 2.0 is a magic number from the original JOSM source code
  double scale = 2.0 * std::min( p.length(), q.length() );

  p = p.normalized();
  q = q.normalized();
  double dotProduct = p * q;

  if ( !dotProductWithinAngleTolerance( dotProduct, lowerThreshold, upperThreshold ) )
  {
    return QgsVector( 0, 0 );
  }

  // wonderful nasty hack which has survived through JOSM -> id -> QGIS
  // to deal with almost-straight segments (angle is closer to 180 than to 90/270).
  if ( dotProduct < -M_SQRT1_2 )
    dotProduct += 1.0;

  QgsVector new_v = p + q;
  // 0.1 magic number from JOSM implementation - think this is to limit each iterative step
  return new_v.normalized() * ( 0.1 * dotProduct * scale );
}

//
// distance of point q from line through p in direction v
// return >0  => q lies left of the line
//        <0  => q lies right of the line
//
double QgsGeometryValidator::distLine2Point( const QgsPoint& p, QgsVector v, const QgsPoint& q )
{
  if ( qgsDoubleNear( v.length(), 0 ) )
  {
    throw QgsException( QObject::tr( "invalid line" ) );
  }

  return ( v.x()*( q.y() - p.y() ) - v.y()*( q.x() - p.x() ) ) / v.length();
}

double normalizedDotProduct( const QgsPoint &a, const QgsPoint &b, const QgsPoint &c )
{
  QgsVector p = a - b;
  QgsVector q = c - b;

  if ( p.length() > 0 )
    p = p.normalized();
  if ( q.length() > 0 )
    q = q.normalized();

  return p * q;
}

void QgsGeometryValidator::checkRingIntersections(
  int p0, int i0, const QgsPolyline &ring0,
  int p1, int i1, const QgsPolyline &ring1 )
{
  for ( int i = 0; !mStop && i < ring0.size() - 1; i++ )
  {
    QgsVector v = ring0[i+1] - ring0[i];

    for ( int j = 0; !mStop && j < ring1.size() - 1; j++ )
    {
      QgsVector w = ring1[j+1] - ring1[j];

      QgsPoint s;
      if ( intersectLines( ring0[i], v, ring1[j], w, s ) )
      {
        double d = -distLine2Point( ring0[i], v.perpVector(), s );

        if ( d >= 0 && d <= v.length() )
        {
          d = -distLine2Point( ring1[j], w.perpVector(), s );
          if ( d > 0 && d < w.length() &&
               ring0[i+1] != ring1[j+1] && ring0[i+1] != ring1[j] &&
               ring0[i+0] != ring1[j+1] && ring0[i+0] != ring1[j] )
          {
            QString msg = QObject::tr( "segment %1 of ring %2 of polygon %3 intersects segment %4 of ring %5 of polygon %6 at %7" )
                          .arg( i0 ).arg( i ).arg( p0 )
                          .arg( i1 ).arg( j ).arg( p1 )
                          .arg( s.toString() );
            QgsDebugMsg( msg );
            emit errorFound( QgsGeometry::Error( msg, s ) );
            mErrorCount++;
          }
        }
      }
    }
  }
}

void QgsGeometryValidator::validatePolyline( int i, QgsPolyline line, bool ring )
{
  if ( ring )
  {
    if ( line.size() < 4 )
    {
      QString msg = QObject::tr( "ring %1 with less than four points" ).arg( i );
      QgsDebugMsg( msg );
      emit errorFound( QgsGeometry::Error( msg ) );
      mErrorCount++;
      return;
    }

    if ( line[0] != line[ line.size()-1 ] )
    {
      QString msg = QObject::tr( "ring %1 not closed" ).arg( i );
      QgsDebugMsg( msg );
      emit errorFound( QgsGeometry::Error( msg ) );
      mErrorCount++;
      return;
    }
  }
  else if ( line.size() < 2 )
  {
    QString msg = QObject::tr( "line %1 with less than two points" ).arg( i );
    QgsDebugMsg( msg );
    emit errorFound( QgsGeometry::Error( msg ) );
    mErrorCount++;
    return;
  }

  int j = 0;
  while ( j < line.size() - 1 )
  {
    int n = 0;
    while ( j < line.size() - 1 && line[j] == line[j+1] )
    {
      line.remove( j );
      n++;
    }

    if ( n > 0 )
    {
      QString msg = QObject::tr( "line %1 contains %n duplicate node(s) at %2", "number of duplicate nodes", n ).arg( i ).arg( j );
      QgsDebugMsg( msg );
      emit errorFound( QgsGeometry::Error( msg, line[j] ) );
      mErrorCount++;
    }

    j++;
  }

  for ( j = 0; !mStop && j < line.size() - 3; j++ )
  {
    QgsVector v = line[j+1] - line[j];
    double vl = v.length();

    int n = ( j == 0 && ring ) ? line.size() - 2 : line.size() - 1;

    for ( int k = j + 2; !mStop && k < n; k++ )
    {
      QgsVector w = line[k+1] - line[k];

      QgsPoint s;
      if ( !intersectLines( line[j], v, line[k], w, s ) )
        continue;

      double d = 0.0;
      try
      {
        d = -distLine2Point( line[j], v.perpVector(), s );
      }
      catch ( QgsException & e )
      {
        Q_UNUSED( e );
        QgsDebugMsg( "Error validating: " + e.what() );
        continue;
      }
      if ( d < 0 || d > vl )
        continue;

      try
      {
        d = -distLine2Point( line[k], w.perpVector(), s );
      }
      catch ( QgsException & e )
      {
        Q_UNUSED( e );
        QgsDebugMsg( "Error validating: " + e.what() );
        continue;
      }

      if ( d <= 0 || d >= w.length() )
        continue;

      QString msg = QObject::tr( "segments %1 and %2 of line %3 intersect at %4" ).arg( j ).arg( k ).arg( i ).arg( s.toString() );
      QgsDebugMsg( msg );
      emit errorFound( QgsGeometry::Error( msg, s ) );
      mErrorCount++;
    }
//.........这里部分代码省略.........