Update qgsrasterfilewriter.cpp

Bad geo-referencing bug fix

Using VRT with large coordinate system (like RGF93/CCxx) and high
resolution raster, highest resolution tiles were shifted regardingi
original raster.
It seemed that when creating the VRT file, georeferencing is
truncated while converted to text, leading to loss of precision.

src/core/raster/qgsrasterfilewriter.cpp

@@ -815,8 +815,8 @@ void QgsRasterFileWriter::createVRT( int xSize, int ySize, const QgsCoordinateRe
   if ( geoTransform )
   {
     QDomElement geoTransformElem = mVRTDocument.createElement( QStringLiteral( "GeoTransform" ) );
-    QString geoTransformString = QString::number( geoTransform[0] ) + ", " + QString::number( geoTransform[1] ) + ", " + QString::number( geoTransform[2] ) +
-                                 ", "  + QString::number( geoTransform[3] ) + ", " + QString::number( geoTransform[4] ) + ", " + QString::number( geoTransform[5] );
+    QString geoTransformString = QString::number( geoTransform[0], 'f', 6 ) + ", " + QString::number( geoTransform[1] ) + ", " + QString::number( geoTransform[2] ) +
+                                 ", "  + QString::number( geoTransform[3], 'f', 6 ) + ", " + QString::number( geoTransform[4] ) + ", " + QString::number( geoTransform[5] );
     QDomText geoTransformText = mVRTDocument.createTextNode( geoTransformString );
     geoTransformElem.appendChild( geoTransformText );
     VRTDatasetElem.appendChild( geoTransformElem );

tests/src/core/testqgsrasterfilewriter.cpp

@@ -50,6 +50,7 @@ class TestQgsRasterFileWriter: public QObject
     void writeTest();
     void testCreateOneBandRaster();
     void testCreateMultiBandRaster();
+    void testVrtCreation();
   private:
     bool writeTest( const QString &rasterName );
     void log( const QString &msg );
@@ -271,6 +272,52 @@ void TestQgsRasterFileWriter::testCreateMultiBandRaster()
   delete rlayer;
 }
 
+void TestQgsRasterFileWriter::testVrtCreation()
+{
+  //create a raster layer that will be used in all tests...
+  QString srcFileName = mTestDataDir + QStringLiteral( "ALLINGES_RGF93_CC46_1_1.tif" );
+  QFileInfo rasterFileInfo( srcFileName );
+  std::unique_ptr< QgsRasterLayer > srcRasterLayer = qgis::make_unique< QgsRasterLayer >( rasterFileInfo.absoluteFilePath(), rasterFileInfo.completeBaseName() );
+
+  QTemporaryDir dir;
+  std::unique_ptr< QgsRasterFileWriter > rasterFileWriter = qgis::make_unique< QgsRasterFileWriter >( dir.path() + '/' + rasterFileInfo.completeBaseName() );
+
+  //2. Definition of the pyramid levels
+  QList<int> levelList;
+  levelList << 2 << 4 << 8 << 16 << 32 << 64 << 128;
+  rasterFileWriter->setPyramidsList( levelList );
+  //3. Pyramid format
+  rasterFileWriter->setPyramidsFormat( QgsRaster::PyramidsGTiff );
+  //4. Resampling method
+  rasterFileWriter->setPyramidsResampling( QStringLiteral( "NEAREST" ) );
+  //5. Tiled mode => true for vrt creation
+  rasterFileWriter->setTiledMode( true );
+  //6. Tile size
+  rasterFileWriter->setMaxTileWidth( 500 );
+  rasterFileWriter->setMaxTileHeight( 500 );
+  //7. Coordinate Reference System
+  QgsCoordinateReferenceSystem crs;
+  crs.createFromString( "EPSG:3946" );
+  //8. Prepare raster pipe
+  QgsRasterPipe pipe;
+  pipe.set( srcRasterLayer->dataProvider()->clone() );
+  // Let's do it !
+  QgsRasterFileWriter::WriterError res = rasterFileWriter->writeRaster( &pipe, srcRasterLayer->width(), srcRasterLayer->height(), srcRasterLayer->extent(), crs );
+  QCOMPARE( res, QgsRasterFileWriter::NoError );
+
+  // Now let's compare the georef of the original raster with the georef of the generated vrt file
+  std::unique_ptr< QgsRasterLayer > vrtRasterLayer = qgis::make_unique< QgsRasterLayer >( dir.path() + '/' + rasterFileInfo.completeBaseName() + '/' + rasterFileInfo.completeBaseName() + QStringLiteral( ".vrt" ), rasterFileInfo.completeBaseName() );
+
+  double xminVrt = vrtRasterLayer->extent().xMinimum();
+  double yminVrt = vrtRasterLayer->extent().yMaximum();
+  double xminOriginal = srcRasterLayer->extent().xMinimum();
+  double yminOriginal = srcRasterLayer->extent().yMaximum();
+
+  // Let's check if the georef of the original raster with the georef of the generated vrt file
+  QGSCOMPARENEAR( xminVrt, xminOriginal, srcRasterLayer->rasterUnitsPerPixelX() / 4 );
+  QGSCOMPARENEAR( yminVrt, yminOriginal, srcRasterLayer->rasterUnitsPerPixelY() / 4 );
+}
+
 void TestQgsRasterFileWriter::log( const QString &msg )
 {
   mReport += msg + "<br>";

tests/testdata/ALLINGES_RGF93_CC46_1_1.tfw

@@ -0,0 +1,6 @@
+0.020000000000
+0
+0
+-0.020000000000
+1964499.715750000207
+5242972.348840000108