Add utility function to convert QgsCoordinateReferenceSystem to OGR SRS

and include coordinate epoch for GDAL 3.4+
qgis · Aug 8, 2021 · fbee77c · fbee77c
1 parent 906b7f0
commit fbee77c
Show file tree

Hide file tree

Showing 3 changed files with 72 additions and 0 deletions.
diff --git a/src/core/qgsogrutils.cpp b/src/core/qgsogrutils.cpp
@@ -957,7 +957,37 @@ QgsCoordinateReferenceSystem QgsOgrUtils::OGRSpatialReferenceToCrs( OGRSpatialRe
   if ( wkt.isEmpty() )
     return QgsCoordinateReferenceSystem();
 
+#if GDAL_VERSION_NUM >= GDAL_COMPUTE_VERSION(3,4,0)
+  QgsCoordinateReferenceSystem res = QgsCoordinateReferenceSystem::fromWkt( wkt );
+  const double coordinateEpoch = OSRGetCoordinateEpoch( srs );
+  if ( coordinateEpoch > 0 )
+    res.setCoordinateEpoch( coordinateEpoch );
+  return res;
+#else
   return QgsCoordinateReferenceSystem::fromWkt( wkt );
+#endif
+}
+
+OGRSpatialReferenceH QgsOgrUtils::crsToOGRSpatialReference( const QgsCoordinateReferenceSystem &crs )
+{
+  if ( crs.isValid() )
+  {
+    const QString srsWkt = crs.toWkt( QgsCoordinateReferenceSystem::WKT_PREFERRED_GDAL );
+
+    if ( OGRSpatialReferenceH ogrSrs = OSRNewSpatialReference( srsWkt.toLocal8Bit().constData() ) )
+    {
+      OSRSetAxisMappingStrategy( ogrSrs, OAMS_TRADITIONAL_GIS_ORDER );
+#if GDAL_VERSION_NUM >= GDAL_COMPUTE_VERSION(3,4,0)
+      if ( !std::isnan( crs.coordinateEpoch() ) )
+      {
+        OSRSetCoordinateEpoch( ogrSrs, crs.coordinateEpoch() );
+      }
+#endif
+      return ogrSrs;
+    }
+  }
+
+  return nullptr;
 }
 
 QString QgsOgrUtils::readShapefileEncoding( const QString &path )

diff --git a/src/core/qgsogrutils.h b/src/core/qgsogrutils.h
@@ -294,6 +294,15 @@ class CORE_EXPORT QgsOgrUtils
      */
     static QgsCoordinateReferenceSystem OGRSpatialReferenceToCrs( OGRSpatialReferenceH srs );
 
+    /**
+     * Returns a OGRSpatialReferenceH corresponding to the specified \a crs object.
+     *
+     * \note Caller must release the returned object with OSRRelease.
+     *
+     * \since QGIS 3.22
+     */
+    static OGRSpatialReferenceH crsToOGRSpatialReference( const QgsCoordinateReferenceSystem &crs );
+
     /**
      * Reads the encoding of the shapefile at the specified \a path (where \a path is the
      * location of the ".shp" file).

diff --git a/tests/src/core/testqgsogrutils.cpp b/tests/src/core/testqgsogrutils.cpp
@@ -21,6 +21,8 @@
 #include <ogr_api.h>
 #include "cpl_conv.h"
 #include "cpl_string.h"
+#include <ogr_srs_api.h>
+#include <gdal.h>
 
 #include "qgsfield.h"
 #include "qgsgeometry.h"
@@ -57,6 +59,7 @@ class TestQgsOgrUtils: public QObject
     void parseStyleString_data();
     void parseStyleString();
     void convertStyleString();
+    void ogrCrsConversion();
 
   private:
 
@@ -716,5 +719,35 @@ void TestQgsOgrUtils::convertStyleString()
   QCOMPARE( qgis::down_cast<QgsSimpleMarkerSymbolLayer * >( symbol->symbolLayer( 0 ) )->strokeStyle(), Qt::NoPen );
 }
 
+void TestQgsOgrUtils::ogrCrsConversion()
+{
+  // test conversion utilities for OGR srs objects
+
+  QgsCoordinateReferenceSystem crs1( QStringLiteral( "EPSG:3111" ) );
+  OGRSpatialReferenceH srs = QgsOgrUtils::crsToOGRSpatialReference( crs1 );
+  QVERIFY( srs );
+  QgsCoordinateReferenceSystem crs2( QgsOgrUtils::OGRSpatialReferenceToCrs( srs ) );
+  // round trip should be lossless
+  QCOMPARE( crs1, crs2 );
+  OSRRelease( srs );
+  srs = nullptr;
+
+#if GDAL_VERSION_NUM >= GDAL_COMPUTE_VERSION(3,4,0)
+  QVERIFY( std::isnan( crs2.coordinateEpoch() ) );
+
+  // test conversion with a coordinate epoch, should work on GDAL 3.4+
+  crs1 = QgsCoordinateReferenceSystem( QStringLiteral( "EPSG:4326" ) );
+  crs1.setCoordinateEpoch( 2020.7 );
+  srs = QgsOgrUtils::crsToOGRSpatialReference( crs1 );
+  QVERIFY( srs );
+  crs2 = QgsCoordinateReferenceSystem( QgsOgrUtils::OGRSpatialReferenceToCrs( srs ) );
+  // round trip should be lossless
+  QCOMPARE( crs1, crs2 );
+  QCOMPARE( crs2.coordinateEpoch(), 2020.7 );
+  OSRRelease( srs );
+  srs = nullptr;
+#endif
+}
+
 QGSTEST_MAIN( TestQgsOgrUtils )
 #include "testqgsogrutils.moc"