double QgsScaleCalculator::calculate( const QgsRectangle &mapExtent, int canvasWidth )
{
double conversionFactor = 0;
double delta = 0;
// calculation is based on the map units and extent, the dpi of the
// users display, and the canvas width
switch ( mMapUnits )
{
case QGis::Meters:
// convert meters to inches
conversionFactor = 39.3700787;
delta = mapExtent.xMaximum() - mapExtent.xMinimum();
break;
case QGis::Feet:
conversionFactor = 12.0;
delta = mapExtent.xMaximum() - mapExtent.xMinimum();
break;
default:
case QGis::Degrees:
// degrees require conversion to meters first
conversionFactor = 39.3700787;
delta = calculateGeographicDistance( mapExtent );
break;
}
if ( canvasWidth == 0 || mDpi == 0 )
{
QgsDebugMsg( "Can't calculate scale from the input values" );
return 0;
}
double scale = ( delta * conversionFactor ) / (( double )canvasWidth / mDpi );
QgsDebugMsg( QString( "scale = %1 conversionFactor = %2" ).arg( scale ).arg( conversionFactor ) );
return scale;
}
double QgsScaleCalculator::calculate( const QgsRectangle &mapExtent, double canvasWidth )
{
double conversionFactor = 0;
double delta = 0;
// calculation is based on the map units and extent, the dpi of the
// users display, and the canvas width
switch ( mMapUnits )
{
case QgsUnitTypes::DistanceMeters:
// convert meters to inches
conversionFactor = 39.3700787;
delta = mapExtent.xMaximum() - mapExtent.xMinimum();
break;
case QgsUnitTypes::DistanceFeet:
conversionFactor = 12.0;
delta = mapExtent.xMaximum() - mapExtent.xMinimum();
break;
case QgsUnitTypes::DistanceNauticalMiles:
// convert nautical miles to inches
conversionFactor = 72913.4;
delta = mapExtent.xMaximum() - mapExtent.xMinimum();
break;
default:
case QgsUnitTypes::DistanceDegrees:
// degrees require conversion to meters first
conversionFactor = 39.3700787;
delta = calculateGeographicDistance( mapExtent );
break;
}
if ( qgsDoubleNear( canvasWidth, 0. ) || qgsDoubleNear( mDpi, 0.0 ) )
{
QgsDebugMsg( QStringLiteral( "Can't calculate scale from the input values" ) );
return 0;
}
double scale = ( delta * conversionFactor ) / ( static_cast< double >( canvasWidth ) / mDpi );
QgsDebugMsgLevel( QStringLiteral( "scale = %1 conversionFactor = %2" ).arg( scale ).arg( conversionFactor ), 4 );
return scale;
}
