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qgsmaptopixelgeometrysimplifier.cpp
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qgsmaptopixelgeometrysimplifier.cpp
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/***************************************************************************
qgsmaptopixelgeometrysimplifier.cpp
---------------------
begin : December 2013
copyright : (C) 2013 by Alvaro Huarte
email : http://wiki.osgeo.org/wiki/Alvaro_Huarte
***************************************************************************
* *
* 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. *
* *
***************************************************************************/
#include <limits>
#include <memory>
#include "qgsmaptopixelgeometrysimplifier.h"
#include "qgsapplication.h"
#include "qgslogger.h"
#include "qgsrectangle.h"
#include "qgswkbptr.h"
#include "qgsgeometry.h"
#include "qgslinestring.h"
#include "qgspolygon.h"
#include "qgsgeometrycollection.h"
QgsMapToPixelSimplifier::QgsMapToPixelSimplifier( int simplifyFlags, double tolerance, SimplifyAlgorithm simplifyAlgorithm )
: mSimplifyFlags( simplifyFlags )
, mSimplifyAlgorithm( simplifyAlgorithm )
, mTolerance( tolerance )
{
}
//////////////////////////////////////////////////////////////////////////////////////////////
// Helper simplification methods
float QgsMapToPixelSimplifier::calculateLengthSquared2D( double x1, double y1, double x2, double y2 )
{
float vx = static_cast< float >( x2 - x1 );
float vy = static_cast< float >( y2 - y1 );
return ( vx * vx ) + ( vy * vy );
}
bool QgsMapToPixelSimplifier::equalSnapToGrid( double x1, double y1, double x2, double y2, double gridOriginX, double gridOriginY, float gridInverseSizeXY )
{
int grid_x1 = std::round( ( x1 - gridOriginX ) * gridInverseSizeXY );
int grid_x2 = std::round( ( x2 - gridOriginX ) * gridInverseSizeXY );
if ( grid_x1 != grid_x2 ) return false;
int grid_y1 = std::round( ( y1 - gridOriginY ) * gridInverseSizeXY );
int grid_y2 = std::round( ( y2 - gridOriginY ) * gridInverseSizeXY );
return grid_y1 == grid_y2;
}
//////////////////////////////////////////////////////////////////////////////////////////////
// Helper simplification methods for Visvalingam method
// It uses a refactored code of the liblwgeom implementation:
// https://github.com/postgis/postgis/blob/svn-trunk/liblwgeom/effectivearea.h
// https://github.com/postgis/postgis/blob/svn-trunk/liblwgeom/effectivearea.c
#include "simplify/effectivearea.h"
//////////////////////////////////////////////////////////////////////////////////////////////
//! Generalize the WKB-geometry using the BBOX of the original geometry
static std::unique_ptr< QgsAbstractGeometry > generalizeWkbGeometryByBoundingBox(
QgsWkbTypes::Type wkbType,
const QgsAbstractGeometry &geometry,
const QgsRectangle &envelope,
bool isRing )
{
unsigned int geometryType = QgsWkbTypes::singleType( QgsWkbTypes::flatType( wkbType ) );
// If the geometry is already minimal skip the generalization
int minimumSize = geometryType == QgsWkbTypes::LineString ? 2 : 5;
if ( geometry.nCoordinates() <= minimumSize )
{
return std::unique_ptr< QgsAbstractGeometry >( geometry.clone() );
}
const double x1 = envelope.xMinimum();
const double y1 = envelope.yMinimum();
const double x2 = envelope.xMaximum();
const double y2 = envelope.yMaximum();
// Write the generalized geometry
if ( geometryType == QgsWkbTypes::LineString && !isRing )
{
return qgis::make_unique< QgsLineString >( QVector<double>() << x1 << x2, QVector<double>() << y1 << y2 );
}
else
{
std::unique_ptr< QgsLineString > ext = qgis::make_unique< QgsLineString >(
QVector< double >() << x1
<< x2
<< x2
<< x1
<< x1,
QVector< double >() << y1
<< y1
<< y2
<< y2
<< y1 );
if ( geometryType == QgsWkbTypes::LineString )
return std::move( ext );
else
{
std::unique_ptr< QgsPolygon > polygon = qgis::make_unique< QgsPolygon >();
polygon->setExteriorRing( ext.release() );
return std::move( polygon );
}
}
}
std::unique_ptr< QgsAbstractGeometry > QgsMapToPixelSimplifier::simplifyGeometry( int simplifyFlags,
SimplifyAlgorithm simplifyAlgorithm,
const QgsAbstractGeometry &geometry, double map2pixelTol,
bool isaLinearRing )
{
bool isGeneralizable = true;
QgsWkbTypes::Type wkbType = geometry.wkbType();
// Can replace the geometry by its BBOX ?
QgsRectangle envelope = geometry.boundingBox();
if ( ( simplifyFlags & QgsMapToPixelSimplifier::SimplifyEnvelope ) &&
isGeneralizableByMapBoundingBox( envelope, map2pixelTol ) )
{
return generalizeWkbGeometryByBoundingBox( wkbType, geometry, envelope, isaLinearRing );
}
if ( !( simplifyFlags & QgsMapToPixelSimplifier::SimplifyGeometry ) )
isGeneralizable = false;
const QgsWkbTypes::Type flatType = QgsWkbTypes::flatType( wkbType );
// Write the geometry
if ( flatType == QgsWkbTypes::LineString || flatType == QgsWkbTypes::CircularString )
{
const QgsCurve &srcCurve = dynamic_cast<const QgsCurve &>( geometry );
const int numPoints = srcCurve.numPoints();
std::unique_ptr<QgsCurve> output;
QVector< double > lineStringX;
QVector< double > lineStringY;
if ( flatType == QgsWkbTypes::LineString )
{
// if we are making a linestring, we do it in an optimised way by directly constructing
// the final x/y vectors, which avoids calling the slower insertVertex method
lineStringX.reserve( numPoints );
lineStringY.reserve( numPoints );
}
else
{
output.reset( qgsgeometry_cast< QgsCurve * >( srcCurve.createEmptyWithSameType() ) );
}
double x = 0.0, y = 0.0, lastX = 0.0, lastY = 0.0;
QgsRectangle r;
r.setMinimal();
if ( numPoints <= ( isaLinearRing ? 4 : 2 ) )
isGeneralizable = false;
bool isLongSegment;
bool hasLongSegments = false; //-> To avoid replace the simplified geometry by its BBOX when there are 'long' segments.
// Check whether the LinearRing is really closed.
if ( isaLinearRing )
{
isaLinearRing = qgsDoubleNear( srcCurve.xAt( 0 ), srcCurve.xAt( numPoints - 1 ) ) &&
qgsDoubleNear( srcCurve.yAt( 0 ), srcCurve.yAt( numPoints - 1 ) );
}
// Process each vertex...
switch ( simplifyAlgorithm )
{
case SnapToGrid:
{
double gridOriginX = envelope.xMinimum();
double gridOriginY = envelope.yMinimum();
// Use a factor for the maximum displacement distance for simplification, similar as GeoServer does
float gridInverseSizeXY = map2pixelTol != 0 ? ( float )( 1.0f / ( 0.8 * map2pixelTol ) ) : 0.0f;
const double *xData = nullptr;
const double *yData = nullptr;
if ( flatType == QgsWkbTypes::LineString )
{
xData = qgsgeometry_cast< const QgsLineString * >( &srcCurve )->xData();
yData = qgsgeometry_cast< const QgsLineString * >( &srcCurve )->yData();
}
for ( int i = 0; i < numPoints; ++i )
{
if ( xData && yData )
{
x = *xData++;
y = *yData++;
}
else
{
x = srcCurve.xAt( i );
y = srcCurve.yAt( i );
}
if ( i == 0 ||
!isGeneralizable ||
!equalSnapToGrid( x, y, lastX, lastY, gridOriginX, gridOriginY, gridInverseSizeXY ) ||
( !isaLinearRing && ( i == 1 || i >= numPoints - 2 ) ) )
{
if ( output )
output->insertVertex( QgsVertexId( 0, 0, output->numPoints() ), QgsPoint( x, y ) );
else
{
lineStringX.append( x );
lineStringY.append( y );
}
lastX = x;
lastY = y;
}
r.combineExtentWith( x, y );
}
break;
}
case Visvalingam:
{
map2pixelTol *= map2pixelTol; //-> Use mappixelTol for 'Area' calculations.
EFFECTIVE_AREAS ea( srcCurve );
int set_area = 0;
ptarray_calc_areas( &ea, isaLinearRing ? 4 : 2, set_area, map2pixelTol );
for ( int i = 0; i < numPoints; ++i )
{
if ( ea.res_arealist[ i ] > map2pixelTol )
{
if ( output )
output->insertVertex( QgsVertexId( 0, 0, output->numPoints() ), ea.inpts.at( i ) );
else
{
lineStringX.append( ea.inpts.at( i ).x() );
lineStringY.append( ea.inpts.at( i ).y() );
}
}
}
break;
}
case Distance:
{
map2pixelTol *= map2pixelTol; //-> Use mappixelTol for 'LengthSquare' calculations.
const double *xData = nullptr;
const double *yData = nullptr;
if ( flatType == QgsWkbTypes::LineString )
{
xData = qgsgeometry_cast< const QgsLineString * >( &srcCurve )->xData();
yData = qgsgeometry_cast< const QgsLineString * >( &srcCurve )->yData();
}
for ( int i = 0; i < numPoints; ++i )
{
if ( xData && yData )
{
x = *xData++;
y = *yData++;
}
else
{
x = srcCurve.xAt( i );
y = srcCurve.yAt( i );
}
isLongSegment = false;
if ( i == 0 ||
!isGeneralizable ||
( isLongSegment = ( calculateLengthSquared2D( x, y, lastX, lastY ) > map2pixelTol ) ) ||
( !isaLinearRing && ( i == 1 || i >= numPoints - 2 ) ) )
{
if ( output )
output->insertVertex( QgsVertexId( 0, 0, output->numPoints() ), QgsPoint( x, y ) );
else
{
lineStringX.append( x );
lineStringY.append( y );
}
lastX = x;
lastY = y;
hasLongSegments |= isLongSegment;
}
r.combineExtentWith( x, y );
}
}
}
if ( !output )
{
output = qgis::make_unique< QgsLineString >( lineStringX, lineStringY );
}
if ( output->numPoints() < ( isaLinearRing ? 4 : 2 ) )
{
// we simplified the geometry too much!
if ( !hasLongSegments )
{
// approximate the geometry's shape by its bounding box
// (rect for linear ring / one segment for line string)
return generalizeWkbGeometryByBoundingBox( wkbType, geometry, r, isaLinearRing );
}
else
{
// Bad luck! The simplified geometry is invalid and approximation by bounding box
// would create artifacts due to long segments.
// We will return the original geometry
return std::unique_ptr< QgsAbstractGeometry >( geometry.clone() );
}
}
if ( isaLinearRing )
{
// make sure we keep the linear ring closed
if ( !qgsDoubleNear( lastX, output->xAt( 0 ) ) || !qgsDoubleNear( lastY, output->yAt( 0 ) ) )
{
output->insertVertex( QgsVertexId( 0, 0, output->numPoints() ), QgsPoint( output->xAt( 0 ), output->yAt( 0 ) ) );
}
}
return std::move( output );
}
else if ( flatType == QgsWkbTypes::Polygon )
{
const QgsPolygon &srcPolygon = dynamic_cast<const QgsPolygon &>( geometry );
std::unique_ptr<QgsPolygon> polygon( new QgsPolygon() );
std::unique_ptr<QgsAbstractGeometry> extRing = simplifyGeometry( simplifyFlags, simplifyAlgorithm, *srcPolygon.exteriorRing(), map2pixelTol, true );
polygon->setExteriorRing( qgsgeometry_cast<QgsCurve *>( extRing.release() ) );
for ( int i = 0; i < srcPolygon.numInteriorRings(); ++i )
{
const QgsCurve *sub = srcPolygon.interiorRing( i );
std::unique_ptr< QgsAbstractGeometry > ring = simplifyGeometry( simplifyFlags, simplifyAlgorithm, *sub, map2pixelTol, true );
polygon->addInteriorRing( qgsgeometry_cast<QgsCurve *>( ring.release() ) );
}
return std::move( polygon );
}
else if ( QgsWkbTypes::isMultiType( flatType ) )
{
const QgsGeometryCollection &srcCollection = dynamic_cast<const QgsGeometryCollection &>( geometry );
std::unique_ptr<QgsGeometryCollection> collection( srcCollection.createEmptyWithSameType() );
const int numGeoms = srcCollection.numGeometries();
for ( int i = 0; i < numGeoms; ++i )
{
const QgsAbstractGeometry *sub = srcCollection.geometryN( i );
std::unique_ptr< QgsAbstractGeometry > part = simplifyGeometry( simplifyFlags, simplifyAlgorithm, *sub, map2pixelTol, false );
collection->addGeometry( part.release() );
}
return std::move( collection );
}
return std::unique_ptr< QgsAbstractGeometry >( geometry.clone() );
}
//////////////////////////////////////////////////////////////////////////////////////////////
bool QgsMapToPixelSimplifier::isGeneralizableByMapBoundingBox( const QgsRectangle &envelope, double map2pixelTol )
{
// Can replace the geometry by its BBOX ?
return envelope.width() < map2pixelTol && envelope.height() < map2pixelTol;
}
QgsGeometry QgsMapToPixelSimplifier::simplify( const QgsGeometry &geometry ) const
{
if ( geometry.isNull() )
{
return QgsGeometry();
}
if ( mSimplifyFlags == QgsMapToPixelSimplifier::NoFlags )
{
return geometry;
}
// Check whether the geometry can be simplified using the map2pixel context
const QgsWkbTypes::Type singleType = QgsWkbTypes::singleType( geometry.wkbType() );
const QgsWkbTypes::Type flatType = QgsWkbTypes::flatType( singleType );
if ( flatType == QgsWkbTypes::Point )
{
return geometry;
}
const bool isaLinearRing = flatType == QgsWkbTypes::Polygon;
const int numPoints = geometry.constGet()->nCoordinates();
if ( numPoints <= ( isaLinearRing ? 6 : 3 ) )
{
// No simplify simple geometries
return geometry;
}
const QgsRectangle envelope = geometry.boundingBox();
if ( std::max( envelope.width(), envelope.height() ) / numPoints > mTolerance * 2.0 )
{
//points are in average too far apart to lead to any significant simplification
return geometry;
}
return QgsGeometry( simplifyGeometry( mSimplifyFlags, mSimplifyAlgorithm, *geometry.constGet(), mTolerance, false ) );
}