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[FEATURE] New API QgsGeometry::densifyByCount
Densifies a geometry by adding a specified number of vertices
to each segment
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nyalldawson committed Mar 25, 2017
1 parent 2dac2d3 commit 5360b79174866c48d61387b673bb1dcc15d9886a
@@ -541,17 +541,8 @@ class QgsGeometry
* @note added in QGIS 3.0
*/
QgsGeometry extendLine( double startDistance, double endDistance ) const;

/** Returns a simplified version of this geometry using a specified tolerance value */
QgsGeometry simplify( double tolerance ) const;

/**
* Returns the center of mass of a geometry.
* @note for line based geometries, the center point of the line is returned,
* and for point based geometries, the point itself is returned
* @see pointOnSurface()
* @see poleOfInaccessibility()
*/
QgsGeometry simplify( double tolerance ) const;
QgsGeometry densifyByCount( int extraNodesPerSegment ) const;
QgsGeometry centroid() const;

/**
@@ -1576,6 +1576,13 @@ QgsGeometry QgsGeometry::simplify( double tolerance ) const
return QgsGeometry( simplifiedGeom );
}

QgsGeometry QgsGeometry::densifyByCount( int extraNodesPerSegment ) const
{
QgsInternalGeometryEngine engine( *this );

return engine.densifyByCount( extraNodesPerSegment );
}

QgsGeometry QgsGeometry::centroid() const
{
if ( !d->geometry )
@@ -611,6 +611,16 @@ class CORE_EXPORT QgsGeometry
//! Returns a simplified version of this geometry using a specified tolerance value
QgsGeometry simplify( double tolerance ) const;

/**
* Returns a copy of the geometry which has been densified by adding the specified
* number of extra nodes within each segment of the geometry.
* If the geometry has z or m values present then these will be linearly interpolated
* at the added nodes.
* Curved geometry types are automatically segmentized by this routine.
* @node added in QGIS 3.0
*/
QgsGeometry densifyByCount( int extraNodesPerSegment ) const;

/**
* Returns the center of mass of a geometry.
* @note for line based geometries, the center point of the line is returned,
@@ -476,3 +476,134 @@ QgsGeometry QgsInternalGeometryEngine::orthogonalize( double tolerance, int maxI
return QgsGeometry( orthogonalizeGeom( mGeometry, maxIterations, tolerance, lowerThreshold, upperThreshold ) );
}
}

QgsLineString *doDensifyByCount( QgsLineString *ring, int extraNodesPerSegment )
{
QgsPointSequence out;
double multiplier = 1.0 / double( extraNodesPerSegment + 1 );

int nPoints = ring->numPoints();
out.reserve( ( extraNodesPerSegment + 1 ) * nPoints );
bool withZ = ring->is3D();
bool withM = ring->isMeasure();
QgsWkbTypes::Type outType = QgsWkbTypes::Point;
if ( ring->is3D() )
outType = QgsWkbTypes::addZ( outType );
if ( ring->isMeasure() )
outType = QgsWkbTypes::addM( outType );
double x1 = 0;
double x2 = 0;
double y1 = 0;
double y2 = 0;
double z1 = 0;
double z2 = 0;
double m1 = 0;
double m2 = 0;
double xOut = 0;
double yOut = 0;
double zOut = 0;
double mOut = 0;
for ( int i = 0; i < nPoints - 1; ++i )
{
x1 = ring->xAt( i );
x2 = ring->xAt( i + 1 );
y1 = ring->yAt( i );
y2 = ring->yAt( i + 1 );
if ( withZ )
{
z1 = ring->zAt( i );
z2 = ring->zAt( i + 1 );
}
if ( withM )
{
m1 = ring->mAt( i );
m2 = ring->mAt( i + 1 );
}

out << QgsPointV2( outType, x1, y1, z1, m1 );
for ( int j = 0; j < extraNodesPerSegment; ++j )
{
double delta = multiplier * ( j + 1 );
xOut = x1 + delta * ( x2 - x1 );
yOut = y1 + delta * ( y2 - y1 );
if ( withZ )
zOut = z1 + delta * ( z2 - z1 );
if ( withM )
mOut = m1 + delta * ( m2 - m1 );

out << QgsPointV2( outType, xOut, yOut, zOut, mOut );
}
}
out << QgsPointV2( outType, ring->xAt( nPoints - 1 ), ring->yAt( nPoints - 1 ),
withZ ? ring->zAt( nPoints - 1 ) : 0, withM ? ring->mAt( nPoints - 1 ) : 0 );

QgsLineString *result = new QgsLineString();
result->setPoints( out );
return result;
}

QgsAbstractGeometry *densifyGeometryByCount( const QgsAbstractGeometry *geom, int extraNodesPerSegment )
{
std::unique_ptr< QgsAbstractGeometry > segmentizedCopy;
if ( QgsWkbTypes::isCurvedType( geom->wkbType() ) )
{
segmentizedCopy.reset( geom->segmentize() );
geom = segmentizedCopy.get();
}

if ( QgsWkbTypes::geometryType( geom->wkbType() ) == QgsWkbTypes::LineGeometry )
{
return doDensifyByCount( static_cast< QgsLineString * >( geom->clone() ), extraNodesPerSegment );
}
else
{
// polygon
const QgsPolygonV2 *polygon = static_cast< const QgsPolygonV2 * >( geom );
QgsPolygonV2 *result = new QgsPolygonV2();

result->setExteriorRing( doDensifyByCount( static_cast< QgsLineString * >( polygon->exteriorRing()->clone() ),
extraNodesPerSegment ) );
for ( int i = 0; i < polygon->numInteriorRings(); ++i )
{
result->addInteriorRing( doDensifyByCount( static_cast< QgsLineString * >( polygon->interiorRing( i )->clone() ),
extraNodesPerSegment ) );
}

return result;
}
}

QgsGeometry QgsInternalGeometryEngine::densifyByCount( int extraNodesPerSegment ) const
{
if ( !mGeometry )
{
return QgsGeometry();
}

if ( QgsWkbTypes::geometryType( mGeometry->wkbType() ) == QgsWkbTypes::PointGeometry )
{
return QgsGeometry( mGeometry->clone() ); // point geometry, nothing to do
}

if ( const QgsGeometryCollection *gc = dynamic_cast< const QgsGeometryCollection *>( mGeometry ) )
{
int numGeom = gc->numGeometries();
QList< QgsAbstractGeometry * > geometryList;
geometryList.reserve( numGeom );
for ( int i = 0; i < numGeom; ++i )
{
geometryList << densifyGeometryByCount( gc->geometryN( i ), extraNodesPerSegment );
}

QgsGeometry first = QgsGeometry( geometryList.takeAt( 0 ) );
Q_FOREACH ( QgsAbstractGeometry *g, geometryList )
{
first.addPart( g );
}
return first;
}
else
{
return QgsGeometry( densifyGeometryByCount( mGeometry, extraNodesPerSegment ) );
}
}
@@ -71,6 +71,16 @@ class QgsInternalGeometryEngine
*/
QgsGeometry orthogonalize( double tolerance = 1.0E-8, int maxIterations = 1000, double angleThreshold = 15.0 ) const;

/**
* Densifies the geometry by adding the specified number of extra nodes within each
* segment of the geometry.
* If the geometry has z or m values present then these will be linearly interpolated
* at the added nodes.
* Curved geometry types are automatically segmentized by this routine.
* @node added in QGIS 3.0
*/
QgsGeometry densifyByCount( int extraNodesPerSegment ) const;

private:
const QgsAbstractGeometry *mGeometry = nullptr;
};
@@ -3894,6 +3894,107 @@ def testVoronoi(self):
self.assertTrue(compareWkt(result, exp, 0.00001),
"delaunay: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))

def testDensifyByCount(self):

empty = QgsGeometry()
o = empty.densifyByCount(4)
self.assertFalse(o)

# point
input = QgsGeometry.fromWkt("PointZ( 1 2 3 )")
o = input.densifyByCount(100)
exp = "PointZ( 1 2 3 )"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))
input = QgsGeometry.fromWkt(
"MULTIPOINT ((155 271), (150 360), (260 360), (271 265), (280 260), (270 370), (154 354), (150 260))")
o = input.densifyByCount(100)
exp = "MULTIPOINT ((155 271), (150 360), (260 360), (271 265), (280 260), (270 370), (154 354), (150 260))"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))

# line
input = QgsGeometry.fromWkt("LineString( 0 0, 10 0, 10 10 )")
o = input.densifyByCount(0)
exp = "LineString( 0 0, 10 0, 10 10 )"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))
o = input.densifyByCount(1)
exp = "LineString( 0 0, 5 0, 10 0, 10 5, 10 10 )"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))
o = input.densifyByCount(3)
exp = "LineString( 0 0, 2.5 0, 5 0, 7.5 0, 10 0, 10 2.5, 10 5, 10 7.5, 10 10 )"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))
input = QgsGeometry.fromWkt("LineStringZ( 0 0 1, 10 0 2, 10 10 0)")
o = input.densifyByCount(1)
exp = "LineStringZ( 0 0 1, 5 0 1.5, 10 0 2, 10 5 1, 10 10 0 )"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))
input = QgsGeometry.fromWkt("LineStringM( 0 0 0, 10 0 2, 10 10 0)")
o = input.densifyByCount(1)
exp = "LineStringM( 0 0 0, 5 0 1, 10 0 2, 10 5 1, 10 10 0 )"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))
input = QgsGeometry.fromWkt("LineStringZM( 0 0 1 10, 10 0 2 8, 10 10 0 4)")
o = input.densifyByCount(1)
exp = "LineStringZM( 0 0 1 10, 5 0 1.5 9, 10 0 2 8, 10 5 1 6, 10 10 0 4 )"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))

# polygon
input = QgsGeometry.fromWkt("Polygon(( 0 0, 10 0, 10 10, 0 0 ))")
o = input.densifyByCount(0)
exp = "Polygon(( 0 0, 10 0, 10 10, 0 0 ))"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))

input = QgsGeometry.fromWkt("PolygonZ(( 0 0 1, 10 0 2, 10 10 0, 0 0 1 ))")
o = input.densifyByCount(1)
exp = "PolygonZ(( 0 0 1, 5 0 1.5, 10 0 2, 10 5 1, 10 10 0, 5 5 0.5, 0 0 1 ))"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))

input = QgsGeometry.fromWkt("PolygonZM(( 0 0 1 4, 10 0 2 6, 10 10 0 8, 0 0 1 4 ))")
o = input.densifyByCount(1)
exp = "PolygonZM(( 0 0 1 4, 5 0 1.5 5, 10 0 2 6, 10 5 1 7, 10 10 0 8, 5 5 0.5 6, 0 0 1 4 ))"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))
# (not strictly valid, but shouldn't matter!
input = QgsGeometry.fromWkt("PolygonZM(( 0 0 1 4, 10 0 2 6, 10 10 0 8, 0 0 1 4 ), ( 0 0 1 4, 10 0 2 6, 10 10 0 8, 0 0 1 4 ) )")
o = input.densifyByCount(1)
exp = "PolygonZM(( 0 0 1 4, 5 0 1.5 5, 10 0 2 6, 10 5 1 7, 10 10 0 8, 5 5 0.5 6, 0 0 1 4 ),( 0 0 1 4, 5 0 1.5 5, 10 0 2 6, 10 5 1 7, 10 10 0 8, 5 5 0.5 6, 0 0 1 4 ))"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))

# multi line
input = QgsGeometry.fromWkt("MultiLineString(( 0 0, 5 0, 10 0, 10 5, 10 10), (20 0, 25 0, 30 0, 30 5, 30 10 ) )")
o = input.densifyByCount(1)
exp = "MultiLineString(( 0 0, 2.5 0, 5 0, 7.5 0, 10 0, 10 2.5, 10 5, 10 7.5, 10 10 ),( 20 0, 22.5 0, 25 0, 27.5 0, 30 0, 30 2.5, 30 5, 30 7.5, 30 10 ))"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))

# multipolygon
input = QgsGeometry.fromWkt("MultiPolygonZ((( 0 0 1, 10 0 2, 10 10 0, 0 0 1)),(( 0 0 1, 10 0 2, 10 10 0, 0 0 1 )))")
o = input.densifyByCount(1)
exp = "MultiPolygonZ((( 0 0 1, 5 0 1.5, 10 0 2, 10 5 1, 10 10 0, 5 5 0.5, 0 0 1 )),(( 0 0 1, 5 0 1.5, 10 0 2, 10 5 1, 10 10 0, 5 5 0.5, 0 0 1 )))"
result = o.exportToWkt()
self.assertTrue(compareWkt(result, exp, 0.00001),
"densify by count: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))

if __name__ == '__main__':
unittest.main()

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