#9060: define global unit conversor

Author: ahuarte47

src/core/qgis.cpp

@@ -112,6 +112,56 @@ QString QGis::tr( QGis::UnitType unit )
   return QCoreApplication::translate( "QGis::UnitType", qPrintable( toLiteral( unit ) ) );
 }
 
+double QGis::fromUnitToUnitFactor( QGis::UnitType fromUnit, QGis::UnitType toUnit )
+{
+  #define DEGREE_TO_METER 111319.49079327358
+  #define FEET_TO_METER 0.3048
+  #define NMILE_TO_METER 1852.0
+
+  // Unify degree units
+  if ( fromUnit == QGis::DecimalDegrees || fromUnit == QGis::DegreesMinutesSeconds || fromUnit == QGis::DegreesDecimalMinutes ) 
+    fromUnit = QGis::Degrees;
+  if ( toUnit == QGis::DecimalDegrees || toUnit == QGis::DegreesMinutesSeconds || toUnit == QGis::DegreesDecimalMinutes ) 
+    toUnit = QGis::Degrees;
+
+  // Calculate the conversion factor between the specified units
+  if ( fromUnit != toUnit && fromUnit != QGis::UnknownUnit && toUnit != QGis::UnknownUnit )
+  {
+    switch ( fromUnit )
+    {
+      case QGis::Meters:
+      {
+        if ( toUnit == QGis::Feet ) return 1.0 / FEET_TO_METER;
+        if ( toUnit == QGis::Degrees ) return 1.0 / DEGREE_TO_METER;
+        if ( toUnit == QGis::NauticalMiles ) return 1.0 / NMILE_TO_METER;
+        break;
+      }
+      case QGis::Feet:
+      {
+        if ( toUnit == QGis::Meters ) return FEET_TO_METER;
+        if ( toUnit == QGis::Degrees ) return FEET_TO_METER / DEGREE_TO_METER;
+        if ( toUnit == QGis::NauticalMiles ) return FEET_TO_METER / NMILE_TO_METER;
+        break;
+      }
+      case QGis::Degrees:
+      {
+        if ( toUnit == QGis::Meters ) return DEGREE_TO_METER;
+        if ( toUnit == QGis::Feet ) return DEGREE_TO_METER / FEET_TO_METER;
+        if ( toUnit == QGis::NauticalMiles ) return DEGREE_TO_METER / NMILE_TO_METER;
+        break;
+      }
+      case QGis::NauticalMiles:
+      {
+        if ( toUnit == QGis::Meters ) return NMILE_TO_METER;
+        if ( toUnit == QGis::Feet ) return NMILE_TO_METER / FEET_TO_METER;
+        if ( toUnit == QGis::Degrees ) return NMILE_TO_METER / DEGREE_TO_METER;
+        break;
+      }
+    }
+  }
+  return 1.0;
+}
+
 void *qgsMalloc( size_t size )
 {
   if ( size == 0 || long( size ) < 0 )

src/core/qgis.h

@@ -248,6 +248,8 @@ class CORE_EXPORT QGis
     //! Provides translated version of the type value
     // Added in version 2.0
     static QString tr( QGis::UnitType unit );
+    //! Returns the conversion factor between the specified units
+    static double fromUnitToUnitFactor( QGis::UnitType fromUnit, QGis::UnitType toUnit );
 
     //! User defined event types
     enum UserEvent