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Optimise QgsLineString::snappedToGrid

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The old approach was quite inefficient and resulted in many
reallocations and array resizing
This commit is contained in:
Nyall Dawson 2024-06-03 13:53:18 +10:00
parent 08b9624f74
commit fbdc9cd5c3
1 changed files with 65 additions and 8 deletions
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73
src/core/geometry/qgslinestring.cpp
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@ -328,15 +328,72 @@ bool QgsLineString::isValid( QString &error, Qgis::GeometryValidityFlags flags )
QgsLineString *QgsLineString::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing ) const
{
// prepare result
std::unique_ptr<QgsLineString> result { createEmptyWithSameType() };
bool res = snapToGridPrivate( hSpacing, vSpacing, dSpacing, mSpacing, mX, mY, mZ, mM,
result->mX, result->mY, result->mZ, result->mM );
if ( res )
return result.release();
else
const int length = numPoints();
if ( length < 2 )
return nullptr;
const bool hasZ = is3D();
const bool hasM = isMeasure();
QVector< double > outX;
outX.reserve( length );
QVector< double > outY;
outY.reserve( length );
QVector< double > outZ;
if ( hasZ )
outZ.reserve( length );
QVector< double > outM;
if ( hasM )
outM.reserve( length );
const double *xIn = mX.constData();
const double *yIn = mY.constData();
const double *zIn = hasZ ? mZ.constData() : nullptr;
const double *mIn = hasM ? mM.constData() : nullptr;
double previousX = 0;
double previousY = 0;
double previousZ = 0;
double previousM = 0;
for ( int i = 0; i < length; ++i )
{
const double currentX = *xIn++;
const double currentY = *yIn++;
const double currentZ = zIn ? *zIn++ : 0;
const double currentM = mIn ? *mIn++ : 0;
const double roundedX = hSpacing > 0 ? ( std::round( currentX / hSpacing ) * hSpacing ) : currentX;
const double roundedY = vSpacing > 0 ? ( std::round( currentY / vSpacing ) * vSpacing ) : currentY;
const double roundedZ = hasZ && dSpacing > 0 ? ( std::round( currentZ / dSpacing ) * dSpacing ) : currentZ;
const double roundedM = hasM && mSpacing > 0 ? ( std::round( currentM / mSpacing ) * mSpacing ) : currentM;
if ( i > 0 )
{
const bool isPointEqual = qgsDoubleNear( roundedX, previousX )
&& qgsDoubleNear( roundedY, previousY )
&& ( !hasZ || dSpacing <= 0 || qgsDoubleNear( roundedZ, previousZ ) )
&& ( !hasM || mSpacing <= 0 || qgsDoubleNear( roundedM, previousM ) );
if ( isPointEqual )
continue;
}
outX.append( roundedX );
outY.append( roundedY );
if ( hasZ )
outZ.append( roundedZ );
if ( hasM )
outM.append( roundedM );
previousX = roundedX;
previousY = roundedY;
previousZ = roundedZ;
previousM = roundedM;
}
if ( outX.length() < 2 || ( isClosed() && outX.length() < 4 ) )
return nullptr;
return new QgsLineString( outX, outY, outZ, outM );
}
bool QgsLineString::removeDuplicateNodes( double epsilon, bool useZValues )