Example #1
0
bool Polygon::covers(PointRef& ref) const
{
    GEOSCoordSequence* coords = GEOSCoordSeq_create_r(m_ctx, 1, 3);
    if (!coords)
        throw pdal_error("Unable to allocate coordinate sequence");

    const double x = ref.getFieldAs<double>(Dimension::Id::X);
    const double y = ref.getFieldAs<double>(Dimension::Id::Y);
    const double z = ref.getFieldAs<double>(Dimension::Id::Z);

    if (!GEOSCoordSeq_setX_r(m_ctx, coords, 0, x))
        throw pdal_error("unable to set x for coordinate sequence");
    if (!GEOSCoordSeq_setY_r(m_ctx, coords, 0, y))
        throw pdal_error("unable to set y for coordinate sequence");
    if (!GEOSCoordSeq_setZ_r(m_ctx, coords, 0, z))
        throw pdal_error("unable to set z for coordinate sequence");
    GEOSGeometry* p = GEOSGeom_createPoint_r(m_ctx, coords);
    if (!p)
        throw pdal_error("unable to allocate candidate test point");

    bool covers = (bool)(GEOSPreparedCovers_r(m_ctx, m_prepGeom, p));
    GEOSGeom_destroy_r(m_ctx, p);

    return covers;
}
Example #2
0
void QgsZonalStatistics::statisticsFromMiddlePointTest( void* band, QgsGeometry* poly, int pixelOffsetX,
    int pixelOffsetY, int nCellsX, int nCellsY, double cellSizeX, double cellSizeY, const QgsRectangle& rasterBBox, double& sum, double& count )
{
  double cellCenterX, cellCenterY;

  float* scanLine = ( float * ) CPLMalloc( sizeof( float ) * nCellsX );
  cellCenterY = rasterBBox.yMaximum() - pixelOffsetY * cellSizeY - cellSizeY / 2;
  count = 0;
  sum = 0;

  const GEOSGeometry* polyGeos = poly->asGeos();
  if ( !polyGeos )
  {
    return;
  }

  GEOSContextHandle_t geosctxt = QgsGeometry::getGEOSHandler();
  const GEOSPreparedGeometry* polyGeosPrepared = GEOSPrepare_r( geosctxt, poly->asGeos() );
  if ( !polyGeosPrepared )
  {
    return;
  }

  GEOSCoordSequence* cellCenterCoords = 0;
  GEOSGeometry* currentCellCenter = 0;

  for ( int i = 0; i < nCellsY; ++i )
  {
    if ( GDALRasterIO( band, GF_Read, pixelOffsetX, pixelOffsetY + i, nCellsX, 1, scanLine, nCellsX, 1, GDT_Float32, 0, 0 )
         != CPLE_None )
    {
      continue;
    }
    cellCenterX = rasterBBox.xMinimum() + pixelOffsetX * cellSizeX + cellSizeX / 2;
    for ( int j = 0; j < nCellsX; ++j )
    {
      GEOSGeom_destroy_r( geosctxt, currentCellCenter );
      cellCenterCoords = GEOSCoordSeq_create_r( geosctxt, 1, 2 );
      GEOSCoordSeq_setX_r( geosctxt, cellCenterCoords, 0, cellCenterX );
      GEOSCoordSeq_setY_r( geosctxt, cellCenterCoords, 0, cellCenterY );
      currentCellCenter = GEOSGeom_createPoint_r( geosctxt, cellCenterCoords );

      if ( scanLine[j] != mInputNodataValue ) //don't consider nodata values
      {
        if ( GEOSPreparedContains_r( geosctxt, polyGeosPrepared, currentCellCenter ) )
        {
          if ( !qIsNaN( scanLine[j] ) )
          {
            sum += scanLine[j];
          }
          ++count;
        }
      }
      cellCenterX += cellSizeX;
    }
    cellCenterY -= cellSizeY;
  }
  CPLFree( scanLine );
  GEOSPreparedGeom_destroy_r( geosctxt, polyGeosPrepared );
}
Example #3
0
void Crop::crop(PointBuffer& input, PointBuffer& output)
{
    bool logOutput = (log()->getLevel() > LogLevel::Debug4);
    if (logOutput)
        log()->floatPrecision(8);

    for (PointId idx = 0; idx < input.size(); ++idx)
    {
        double x = input.getFieldAs<double>(Dimension::Id::X, idx);
        double y = input.getFieldAs<double>(Dimension::Id::Y, idx);
        double z = input.getFieldAs<double>(Dimension::Id::Z, idx);

        if (logOutput)
        {
            log()->floatPrecision(10);
            log()->get(LogLevel::Debug5) << "input: " << x << " y: " << y <<
                " z: " << z << std::endl;
        }

        if (m_poly.empty())
        {
            // We don't have a polygon, just a bounds. Filter on that
            // by itself.
            if (!m_cropOutside && m_bounds.contains(x, y, z))
                output.appendPoint(input, idx);
        }
#ifdef PDAL_HAVE_GEOS
        else
        {
            int ret(0);

            // precise filtering based on the geometry
            GEOSCoordSequence* coords =
                GEOSCoordSeq_create_r(m_geosEnvironment, 1, 3);
            if (!coords)
                throw pdal_error("unable to allocate coordinate sequence");
            ret = GEOSCoordSeq_setX_r(m_geosEnvironment, coords, 0, x);
            if (!ret)
                throw pdal_error("unable to set x for coordinate sequence");
            ret = GEOSCoordSeq_setY_r(m_geosEnvironment, coords, 0, y);
            if (!ret)
                throw pdal_error("unable to set y for coordinate sequence");
            ret = GEOSCoordSeq_setZ_r(m_geosEnvironment, coords, 0, z);
            if (!ret)
                throw pdal_error("unable to set z for coordinate sequence");

            GEOSGeometry* p = GEOSGeom_createPoint_r(m_geosEnvironment, coords);
            if (!p)
                throw pdal_error("unable to allocate candidate test point");

            if (static_cast<bool>(GEOSPreparedContains_r(m_geosEnvironment,
                m_geosPreparedGeometry, p)) != m_cropOutside)
                output.appendPoint(input, idx);
            GEOSGeom_destroy_r(m_geosEnvironment, p);
        }
#endif
    }
}
void QgsZonalStatistics::statisticsFromMiddlePointTest( void* band, const QgsGeometry& poly, int pixelOffsetX,
    int pixelOffsetY, int nCellsX, int nCellsY, double cellSizeX, double cellSizeY, const QgsRectangle& rasterBBox, FeatureStats &stats )
{
  double cellCenterX, cellCenterY;

  float* scanLine = ( float * ) CPLMalloc( sizeof( float ) * nCellsX );
  cellCenterY = rasterBBox.yMaximum() - pixelOffsetY * cellSizeY - cellSizeY / 2;
  stats.reset();

  GEOSGeometry* polyGeos = poly.exportToGeos();
  if ( !polyGeos )
  {
    return;
  }

  GEOSContextHandle_t geosctxt = QgsGeometry::getGEOSHandler();
  const GEOSPreparedGeometry* polyGeosPrepared = GEOSPrepare_r( geosctxt, polyGeos );
  if ( !polyGeosPrepared )
  {
    GEOSGeom_destroy_r( geosctxt, polyGeos );
    return;
  }

  GEOSCoordSequence* cellCenterCoords = nullptr;
  GEOSGeometry* currentCellCenter = nullptr;

  for ( int i = 0; i < nCellsY; ++i )
  {
    if ( GDALRasterIO( band, GF_Read, pixelOffsetX, pixelOffsetY + i, nCellsX, 1, scanLine, nCellsX, 1, GDT_Float32, 0, 0 )
         != CPLE_None )
    {
      continue;
    }
    cellCenterX = rasterBBox.xMinimum() + pixelOffsetX * cellSizeX + cellSizeX / 2;
    for ( int j = 0; j < nCellsX; ++j )
    {
      if ( validPixel( scanLine[j] ) )
      {
        GEOSGeom_destroy_r( geosctxt, currentCellCenter );
        cellCenterCoords = GEOSCoordSeq_create_r( geosctxt, 1, 2 );
        GEOSCoordSeq_setX_r( geosctxt, cellCenterCoords, 0, cellCenterX );
        GEOSCoordSeq_setY_r( geosctxt, cellCenterCoords, 0, cellCenterY );
        currentCellCenter = GEOSGeom_createPoint_r( geosctxt, cellCenterCoords );
        if ( GEOSPreparedContains_r( geosctxt, polyGeosPrepared, currentCellCenter ) )
        {
          stats.addValue( scanLine[j] );
        }
      }
      cellCenterX += cellSizeX;
    }
    cellCenterY -= cellSizeY;
  }
  GEOSGeom_destroy_r( geosctxt, currentCellCenter );
  CPLFree( scanLine );
  GEOSPreparedGeom_destroy_r( geosctxt, polyGeosPrepared );
  GEOSGeom_destroy_r( geosctxt, polyGeos );
}
Example #5
0
void QgsZonalStatistics::statisticsFromMiddlePointTest( const QgsGeometry &poly, int pixelOffsetX,
    int pixelOffsetY, int nCellsX, int nCellsY, double cellSizeX, double cellSizeY, const QgsRectangle &rasterBBox, FeatureStats &stats )
{
  double cellCenterX, cellCenterY;

  cellCenterY = rasterBBox.yMaximum() - pixelOffsetY * cellSizeY - cellSizeY / 2;
  stats.reset();

  GEOSGeometry *polyGeos = poly.exportToGeos();
  if ( !polyGeos )
  {
    return;
  }

  GEOSContextHandle_t geosctxt = QgsGeometry::getGEOSHandler();
  const GEOSPreparedGeometry *polyGeosPrepared = GEOSPrepare_r( geosctxt, polyGeos );
  if ( !polyGeosPrepared )
  {
    GEOSGeom_destroy_r( geosctxt, polyGeos );
    return;
  }

  GEOSCoordSequence *cellCenterCoords = nullptr;
  GEOSGeometry *currentCellCenter = nullptr;

  QgsRectangle featureBBox = poly.boundingBox().intersect( &rasterBBox );
  QgsRectangle intersectBBox = rasterBBox.intersect( &featureBBox );

  QgsRasterBlock *block = mRasterProvider->block( mRasterBand, intersectBBox, nCellsX, nCellsY );
  for ( int i = 0; i < nCellsY; ++i )
  {
    cellCenterX = rasterBBox.xMinimum() + pixelOffsetX * cellSizeX + cellSizeX / 2;
    for ( int j = 0; j < nCellsX; ++j )
    {
      if ( validPixel( block->value( i, j ) ) )
      {
        GEOSGeom_destroy_r( geosctxt, currentCellCenter );
        cellCenterCoords = GEOSCoordSeq_create_r( geosctxt, 1, 2 );
        GEOSCoordSeq_setX_r( geosctxt, cellCenterCoords, 0, cellCenterX );
        GEOSCoordSeq_setY_r( geosctxt, cellCenterCoords, 0, cellCenterY );
        currentCellCenter = GEOSGeom_createPoint_r( geosctxt, cellCenterCoords );
        if ( GEOSPreparedContains_r( geosctxt, polyGeosPrepared, currentCellCenter ) )
        {
          stats.addValue( block->value( i, j ) );
        }
      }
      cellCenterX += cellSizeX;
    }
    cellCenterY -= cellSizeY;
  }

  GEOSGeom_destroy_r( geosctxt, currentCellCenter );
  GEOSPreparedGeom_destroy_r( geosctxt, polyGeosPrepared );
  GEOSGeom_destroy_r( geosctxt, polyGeos );
  delete block;
}
Example #6
0
VALUE rgeo_create_geos_point(VALUE factory, double x, double y, double z)
{
  VALUE result = Qnil;
  RGeo_FactoryData* factory_data = RGEO_FACTORY_DATA_PTR(factory);
  GEOSContextHandle_t context = factory_data->geos_context;
  GEOSCoordSequence* coord_seq = GEOSCoordSeq_create_r(context, 1, 3);
  if (coord_seq) {
    if (GEOSCoordSeq_setX_r(context, coord_seq, 0, x)) {
      if (GEOSCoordSeq_setY_r(context, coord_seq, 0, y)) {
        if (GEOSCoordSeq_setZ_r(context, coord_seq, 0, z)) {
          GEOSGeometry* geom = GEOSGeom_createPoint_r(context, coord_seq);
          if (geom) {
            result = rgeo_wrap_geos_geometry(factory, geom, factory_data->globals->geos_point);
          }
        }
      }
    }
  }
  return result;
}
Example #7
0
State get_state(const Point &point, const GEOSPreparedGeometry *gp_domain,
                GEOSContextHandle_t handle)
{
    State state;

    if (isfinite(point.x) && isfinite(point.y))
    {
        // TODO: Avoid create-destroy
        GEOSCoordSequence *coords = GEOSCoordSeq_create_r(handle, 1, 2);
        GEOSCoordSeq_setX_r(handle, coords, 0, point.x);
        GEOSCoordSeq_setY_r(handle, coords, 0, point.y);
        GEOSGeometry *g_point = GEOSGeom_createPoint_r(handle, coords);
        state = GEOSPreparedCovers_r(handle, gp_domain, g_point) ? POINT_IN : POINT_OUT;
        GEOSGeom_destroy_r(handle, g_point);
    }
    else
    {
        state = POINT_NAN;
    }
    return state;
}
Example #8
0
GEOSGeometry* createGEOSPoint(GEOSContextHandle_t ctx, double x, double y, double z)
{
    int ret(0);

    // precise filtering based on the geometry
    GEOSCoordSequence* coords =
        GEOSCoordSeq_create_r(ctx, 1, 3);
    if (!coords)
        throw pdal_error("unable to allocate coordinate sequence");
    ret = GEOSCoordSeq_setX_r(ctx, coords, 0, x);
    if (!ret)
        throw pdal_error("unable to set x for coordinate sequence");
    ret = GEOSCoordSeq_setY_r(ctx, coords, 0, y);
    if (!ret)
        throw pdal_error("unable to set y for coordinate sequence");
    ret = GEOSCoordSeq_setZ_r(ctx, coords, 0, z);
    if (!ret)
        throw pdal_error("unable to set z for coordinate sequence");

    GEOSGeometry* p = GEOSGeom_createPoint_r(ctx, coords);
    if (!p)
        throw pdal_error("unable to allocate candidate test point");
    return p;
}
QgsGeometry QgsGeometryAnalyzer::createOffsetGeometry( const QgsGeometry& geom, const QgsGeometry& lineGeom, double offset )
{
  if ( !geom || lineGeom.isEmpty() )
  {
    return QgsGeometry();
  }

  QList<QgsGeometry> inputGeomList;

  if ( geom.isMultipart() )
  {
    inputGeomList = geom.asGeometryCollection();
  }
  else
  {
    inputGeomList.push_back( geom );
  }

  QList<GEOSGeometry*> outputGeomList;
  QList<QgsGeometry>::const_iterator inputGeomIt = inputGeomList.constBegin();
  GEOSContextHandle_t geosctxt = QgsGeometry::getGEOSHandler();
  for ( ; inputGeomIt != inputGeomList.constEnd(); ++inputGeomIt )
  {
    if ( geom.type() == QgsWkbTypes::LineGeometry )
    {
      GEOSGeometry* inputGeomItGeos = inputGeomIt->exportToGeos();
      GEOSGeometry* offsetGeom = GEOSOffsetCurve_r( geosctxt, inputGeomItGeos, -offset, 8 /*quadSegments*/, 0 /*joinStyle*/, 5.0 /*mitreLimit*/ );
      GEOSGeom_destroy_r( geosctxt, inputGeomItGeos );
      if ( !offsetGeom || !GEOSisValid_r( geosctxt, offsetGeom ) )
      {
        return QgsGeometry();
      }
      if ( !GEOSisValid_r( geosctxt, offsetGeom ) || GEOSGeomTypeId_r( geosctxt, offsetGeom ) != GEOS_LINESTRING || GEOSGeomGetNumPoints_r( geosctxt, offsetGeom ) < 1 )
      {
        GEOSGeom_destroy_r( geosctxt, offsetGeom );
        return QgsGeometry();
      }
      outputGeomList.push_back( offsetGeom );
    }
    else if ( geom.type() == QgsWkbTypes::PointGeometry )
    {
      QgsPoint p = ( *inputGeomIt ).asPoint();
      p = createPointOffset( p.x(), p.y(), offset, lineGeom );
      GEOSCoordSequence* ptSeq = GEOSCoordSeq_create_r( geosctxt, 1, 2 );
      GEOSCoordSeq_setX_r( geosctxt, ptSeq, 0, p.x() );
      GEOSCoordSeq_setY_r( geosctxt, ptSeq, 0, p.y() );
      GEOSGeometry* geosPt = GEOSGeom_createPoint_r( geosctxt, ptSeq );
      outputGeomList.push_back( geosPt );
    }
  }

  QgsGeometry outGeometry;
  if ( !geom.isMultipart() )
  {
    GEOSGeometry* outputGeom = outputGeomList.at( 0 );
    if ( outputGeom )
    {
      outGeometry.fromGeos( outputGeom );
    }
  }
  else
  {
    GEOSGeometry** geomArray = new GEOSGeometry*[outputGeomList.size()];
    for ( int i = 0; i < outputGeomList.size(); ++i )
    {
      geomArray[i] = outputGeomList.at( i );
    }
    GEOSGeometry* collection = nullptr;
    if ( geom.type() == QgsWkbTypes::PointGeometry )
    {
      collection = GEOSGeom_createCollection_r( geosctxt, GEOS_MULTIPOINT, geomArray, outputGeomList.size() );
    }
    else if ( geom.type() == QgsWkbTypes::LineGeometry )
    {
      collection = GEOSGeom_createCollection_r( geosctxt, GEOS_MULTILINESTRING, geomArray, outputGeomList.size() );
    }
    outGeometry.fromGeos( collection );
    delete[] geomArray;
  }
  return outGeometry;
}
Example #10
0
/*
 * Return whether the given line segment is suitable as an
 * approximation of the projection of the source line.
 *
 * t_start: Interpolation parameter for the start point.
 * p_start: Projected start point.
 * t_end: Interpolation parameter for the end point.
 * p_start: Projected end point.
 * interpolator: Interpolator for current source line.
 * threshold: Lateral tolerance in target projection coordinates.
 * handle: Thread-local context handle for GEOS.
 * gp_domain: Prepared polygon of target map domain.
 * inside: Whether the start point is within the map domain.
 */
bool straightAndDomain(double t_start, const Point &p_start,
                       double t_end, const Point &p_end,
                       Interpolator *interpolator, double threshold,
                       GEOSContextHandle_t handle,
                       const GEOSPreparedGeometry *gp_domain,
                       bool inside)
{
    // Straight and in-domain (de9im[7] == 'F')
    
    bool valid;

    // This could be optimised out of the loop.
    if (!(isfinite(p_start.x) && isfinite(p_start.y)))
    {
        valid = false;
    }
    else if (!(isfinite(p_end.x) && isfinite(p_end.y)))
    {
        valid = false;
    }
    else
    {
        // TODO: Re-use geometries, instead of create-destroy!

        // Create a LineString for the current end-point.
        GEOSCoordSequence *coords = GEOSCoordSeq_create_r(handle, 2, 2);
        GEOSCoordSeq_setX_r(handle, coords, 0, p_start.x);
        GEOSCoordSeq_setY_r(handle, coords, 0, p_start.y);
        GEOSCoordSeq_setX_r(handle, coords, 1, p_end.x);
        GEOSCoordSeq_setY_r(handle, coords, 1, p_end.y);
        GEOSGeometry *g_segment = GEOSGeom_createLineString_r(handle, coords);

        // Find the projected mid-point
        double t_mid = (t_start + t_end) * 0.5;
        Point p_mid = interpolator->interpolate(t_mid);

        // Make it into a GEOS geometry
        coords = GEOSCoordSeq_create_r(handle, 1, 2);
        GEOSCoordSeq_setX_r(handle, coords, 0, p_mid.x);
        GEOSCoordSeq_setY_r(handle, coords, 0, p_mid.y);
        GEOSGeometry *g_mid = GEOSGeom_createPoint_r(handle, coords);

        double along = GEOSProjectNormalized_r(handle, g_segment, g_mid);
        if(isnan(along))
        {
            valid = true;
        }
        else
        {
            valid = 0.0 < along && along < 1.0;
            if (valid)
            {
                double separation;
                GEOSDistance_r(handle, g_segment, g_mid, &separation);
                if (inside)
                {
                    // Scale the lateral threshold by the distance from
                    // the nearest end. I.e. Near the ends the lateral
                    // threshold is much smaller; it only has its full
                    // value in the middle.
                    valid = separation <= threshold * 2.0 *
                                            (0.5 - fabs(0.5 - along));
                }
                else
                {
                    // Check if the mid-point makes less than ~11 degree
                    // angle with the straight line.
                    // sin(11') => 0.2
                    // To save the square-root we just use the square of
                    // the lengths, hence:
                    // 0.2 ^ 2 => 0.04
                    double hypot_dx = p_mid.x - p_start.x;
                    double hypot_dy = p_mid.y - p_start.y;
                    double hypot = hypot_dx * hypot_dx + hypot_dy * hypot_dy;
                    valid = ((separation * separation) / hypot) < 0.04;
                }
            }
        }

        if (valid)
        {
            if(inside)
                valid = GEOSPreparedCovers_r(handle, gp_domain, g_segment);
            else
                valid = GEOSPreparedDisjoint_r(handle, gp_domain, g_segment);
        }

        GEOSGeom_destroy_r(handle, g_segment);
        GEOSGeom_destroy_r(handle, g_mid);
    }

    return valid;
}
Q_NOWARN_UNREACHABLE_POP

// Return Nth vertex in GEOSGeometry as a POINT.
// May return NULL if the geometry has NO vertexex.
static GEOSGeometry *LWGEOM_GEOS_getPointN( const GEOSGeometry *g_in, uint32_t n )
{
  GEOSContextHandle_t handle = QgsGeos::getGEOSHandler();

  uint32_t dims;
  const GEOSCoordSequence *seq_in = nullptr;
  GEOSCoordSeq seq_out;
  double val;
  uint32_t sz;
  int gn;
  GEOSGeometry *ret = nullptr;

  switch ( GEOSGeomTypeId_r( handle, g_in ) )
  {
    case GEOS_MULTIPOINT:
    case GEOS_MULTILINESTRING:
    case GEOS_MULTIPOLYGON:
    case GEOS_GEOMETRYCOLLECTION:
    {
      for ( gn = 0; gn < GEOSGetNumGeometries_r( handle, g_in ); ++gn )
      {
        const GEOSGeometry *g = GEOSGetGeometryN_r( handle, g_in, gn );
        ret = LWGEOM_GEOS_getPointN( g, n );
        if ( ret ) return ret;
      }
      break;
    }

    case GEOS_POLYGON:
    {
      ret = LWGEOM_GEOS_getPointN( GEOSGetExteriorRing_r( handle, g_in ), n );
      if ( ret ) return ret;
      for ( gn = 0; gn < GEOSGetNumInteriorRings_r( handle, g_in ); ++gn )
      {
        const GEOSGeometry *g = GEOSGetInteriorRingN_r( handle, g_in, gn );
        ret = LWGEOM_GEOS_getPointN( g, n );
        if ( ret ) return ret;
      }
      break;
    }

    case GEOS_POINT:
    case GEOS_LINESTRING:
    case GEOS_LINEARRING:
      break;

  }

  seq_in = GEOSGeom_getCoordSeq_r( handle, g_in );
  if ( ! seq_in ) return nullptr;
  if ( ! GEOSCoordSeq_getSize_r( handle, seq_in, &sz ) ) return nullptr;
  if ( ! sz ) return nullptr;

  if ( ! GEOSCoordSeq_getDimensions_r( handle, seq_in, &dims ) ) return nullptr;

  seq_out = GEOSCoordSeq_create_r( handle, 1, dims );
  if ( ! seq_out ) return nullptr;

  if ( ! GEOSCoordSeq_getX_r( handle, seq_in, n, &val ) ) return nullptr;
  if ( ! GEOSCoordSeq_setX_r( handle, seq_out, n, val ) ) return nullptr;
  if ( ! GEOSCoordSeq_getY_r( handle, seq_in, n, &val ) ) return nullptr;
  if ( ! GEOSCoordSeq_setY_r( handle, seq_out, n, val ) ) return nullptr;
  if ( dims > 2 )
  {
    if ( ! GEOSCoordSeq_getZ_r( handle, seq_in, n, &val ) ) return nullptr;
    if ( ! GEOSCoordSeq_setZ_r( handle, seq_out, n, val ) ) return nullptr;
  }

  return GEOSGeom_createPoint_r( handle, seq_out );
}
Example #12
0
bool QgsGeometryAnalyzer::createOffsetGeometry( QgsGeometry* geom, QgsGeometry* lineGeom, double offset )
{
  if ( !geom || !lineGeom )
  {
    return false;
  }

  QList<QgsGeometry*> inputGeomList;

  if ( geom->isMultipart() )
  {
    inputGeomList = geom->asGeometryCollection();
  }
  else
  {
    inputGeomList.push_back( geom );
  }

  QList<GEOSGeometry*> outputGeomList;
  QList<QgsGeometry*>::const_iterator inputGeomIt = inputGeomList.constBegin();
  GEOSContextHandle_t geosctxt = QgsGeometry::getGEOSHandler();
  for ( ; inputGeomIt != inputGeomList.constEnd(); ++inputGeomIt )
  {
    if ( geom->type() == QGis::Line )
    {
      //geos 3.3 needed for line offsets
#if defined(GEOS_VERSION_MAJOR) && defined(GEOS_VERSION_MINOR) && \
      ((GEOS_VERSION_MAJOR>3) || ((GEOS_VERSION_MAJOR==3) && (GEOS_VERSION_MINOR>=3)))
      GEOSGeometry* offsetGeom = GEOSOffsetCurve_r( geosctxt, ( *inputGeomIt )->asGeos(), -offset, 8 /*quadSegments*/, 0 /*joinStyle*/, 5.0 /*mitreLimit*/ );
      if ( !offsetGeom || !GEOSisValid_r( geosctxt, offsetGeom ) )
      {
        return false;
      }
      if ( !GEOSisValid_r( geosctxt, offsetGeom ) || GEOSGeomTypeId_r( geosctxt, offsetGeom ) != GEOS_LINESTRING || GEOSGeomGetNumPoints_r( geosctxt, offsetGeom ) < 1 )
      {
        GEOSGeom_destroy_r( geosctxt, offsetGeom );
        return false;
      }
      outputGeomList.push_back( offsetGeom );
#else
      outputGeomList.push_back( GEOSGeom_clone_r( geosctxt, ( *inputGeomIt )->asGeos() ) );
#endif
    }
    else if ( geom->type() == QGis::Point )
    {
      QgsPoint p = ( *inputGeomIt )->asPoint();
      p = createPointOffset( p.x(), p.y(), offset, lineGeom );
      GEOSCoordSequence* ptSeq = GEOSCoordSeq_create_r( geosctxt, 1, 2 );
      GEOSCoordSeq_setX_r( geosctxt, ptSeq, 0, p.x() );
      GEOSCoordSeq_setY_r( geosctxt, ptSeq, 0, p.y() );
      GEOSGeometry* geosPt = GEOSGeom_createPoint_r( geosctxt, ptSeq );
      outputGeomList.push_back( geosPt );
    }
  }

  if ( !geom->isMultipart() )
  {
    GEOSGeometry* outputGeom = outputGeomList.at( 0 );
    if ( outputGeom )
    {
      geom->fromGeos( outputGeom );
    }
  }
  else
  {
    GEOSGeometry** geomArray = new GEOSGeometry*[outputGeomList.size()];
    for ( int i = 0; i < outputGeomList.size(); ++i )
    {
      geomArray[i] = outputGeomList.at( i );
    }
    GEOSGeometry* collection = 0;
    if ( geom->type() == QGis::Point )
    {
      collection = GEOSGeom_createCollection_r( geosctxt, GEOS_MULTIPOINT, geomArray, outputGeomList.size() );
    }
    else if ( geom->type() == QGis::Line )
    {
      collection = GEOSGeom_createCollection_r( geosctxt, GEOS_MULTILINESTRING, geomArray, outputGeomList.size() );
    }
    geom->fromGeos( collection );
    delete[] geomArray;
  }
  return true;
}