Add argument to QgsCoordinateTransform::transformBoundingBox to flag …

…that handling of a bounding box which crosses the 180 degree longitude line is required. Fix composer map reprojected grids which cross 180 degree line.
qgis · Oct 1, 2014 · a2d5acb · a2d5acb
1 parent d66e4dc
commit a2d5acb
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Showing 6 changed files with 153 additions and 7 deletions.
diff --git a/python/core/qgscoordinatetransform.sip b/python/core/qgscoordinatetransform.sip
@@ -114,9 +114,11 @@ class QgsCoordinateTransform : QObject
      * returned rectangle.
      * @param theRect rect to transform
      * @param direction TransformDirection (defaults to ForwardTransform)
+     * @param handle180Crossover set to true if destination crs is geographic and handling of extents crossing the 180 degree
+     * longitude line is required
      * @return QgsRectangle in Destination Coordinate System
      */
-    QgsRectangle transformBoundingBox( const QgsRectangle theRect, TransformDirection direction = ForwardTransform ) const throw (QgsCsException);
+    QgsRectangle transformBoundingBox( const QgsRectangle theRect, TransformDirection direction = ForwardTransform, const bool handle180Crossover = false ) const throw (QgsCsException);
 
     // Same as for the other transform() functions, but alters the x
     // and y variables in place. The second one works with good old-fashioned

diff --git a/src/core/composer/qgscomposermapgrid.cpp b/src/core/composer/qgscomposermapgrid.cpp
@@ -25,6 +25,7 @@
 #include "qgsrendercontext.h"
 #include "qgssymbollayerv2utils.h"
 #include "qgssymbolv2.h"
+#include "qgscoordinatereferencesystem.h"
 
 #include <QPainter>
 #include <QPen>
@@ -1356,6 +1357,15 @@ int QgsComposerMapGrid::xGridLinesCRSTransform( const QgsRectangle& bbox, const
   double maxX = bbox.xMaximum();
   double step = ( maxX - minX ) / 20;
 
+  bool crosses180 = false;
+  bool crossed180 = false;
+  if ( mCRS.geographicFlag() && ( minX > maxX ) )
+  {
+    //handle 180 degree longitude crossover
+    crosses180 = true;
+    step = ( maxX + 360.0 - minX ) / 20;
+  }
+
   int gridLineCount = 0;
   while ( currentLevel >= bbox.yMinimum() && gridLineCount < MAX_GRID_LINES )
   {
@@ -1364,15 +1374,21 @@ int QgsComposerMapGrid::xGridLinesCRSTransform( const QgsRectangle& bbox, const
     bool cont = true;
     while ( cont )
     {
-      if ( currentX > maxX )
+      if (( !crosses180 || crossed180 ) && ( currentX > maxX ) )
       {
         cont = false;
       }
 
       QgsPoint mapPoint = t.transform( currentX, currentLevel ); //transform back to map crs
       gridLine.append( mComposerMap->mapToItemCoords( QPointF( mapPoint.x(), mapPoint.y() ) ) ); //transform back to composer coords
       currentX += step;
+      if ( crosses180 && currentX > 180.0 )
+      {
+        currentX -= 360.0;
+        crossed180 = true;
+      }
     }
+    crossed180 = false;
 
     gridLine = trimLineToMap( gridLine, QgsRectangle( mComposerMap->rect() ) );
     if ( gridLine.size() > 0 )
@@ -1401,8 +1417,16 @@ int QgsComposerMapGrid::yGridLinesCRSTransform( const QgsRectangle& bbox, const
   double maxY = bbox.yMaximum();
   double step = ( maxY - minY ) / 20;
 
+  bool crosses180 = false;
+  bool crossed180 = false;
+  if ( mCRS.geographicFlag() && ( bbox.xMinimum() > bbox.xMaximum() ) )
+  {
+    //handle 180 degree longitude crossover
+    crosses180 = true;
+  }
+
   int gridLineCount = 0;
-  while ( currentLevel <= bbox.xMaximum() && gridLineCount < MAX_GRID_LINES )
+  while (( currentLevel <= bbox.xMaximum() || ( crosses180 && !crossed180 ) ) && gridLineCount < MAX_GRID_LINES )
   {
     QPolygonF gridLine;
     double currentY = minY;
@@ -1427,6 +1451,11 @@ int QgsComposerMapGrid::yGridLinesCRSTransform( const QgsRectangle& bbox, const
       gridLineCount++;
     }
     currentLevel += mGridIntervalX;
+    if ( crosses180 && currentLevel > 180.0 )
+    {
+      currentLevel -= 360.0;
+      crossed180 = true;
+    }
   }
 
   return 0;
@@ -1735,7 +1764,33 @@ int QgsComposerMapGrid::crsGridParams( QgsRectangle& crsRect, QgsCoordinateTrans
   QPolygonF mapPolygon = mComposerMap->transformedMapPolygon();
   QRectF mbr = mapPolygon.boundingRect();
   QgsRectangle mapBoundingRect( mbr.left(), mbr.bottom(), mbr.right(), mbr.top() );
-  crsRect = tr.transformBoundingBox( mapBoundingRect );
+
+
+  if ( mCRS.geographicFlag() )
+  {
+    //handle crossing the 180 degree longitude line
+    QgsPoint lowerLeft( mapBoundingRect.xMinimum(), mapBoundingRect.yMinimum() );
+    QgsPoint upperRight( mapBoundingRect.xMaximum(), mapBoundingRect.yMaximum() );
+
+    lowerLeft = tr.transform( lowerLeft.x(), lowerLeft.y() );
+    upperRight = tr.transform( upperRight.x(), upperRight.y() );
+
+    if ( lowerLeft.x() > upperRight.x() )
+    {
+      //we've crossed the line
+      crsRect = tr.transformBoundingBox( mapBoundingRect, QgsCoordinateTransform::ForwardTransform, true );
+    }
+    else
+    {
+      //didn't cross the line
+      crsRect = tr.transformBoundingBox( mapBoundingRect );
+    }
+  }
+  else
+  {
+    crsRect = tr.transformBoundingBox( mapBoundingRect );
+  }
+
   inverseTransform.setSourceCrs( mCRS );
   inverseTransform.setDestCRS( mComposerMap->composition()->mapSettings().destinationCrs() );
   return 0;

diff --git a/src/core/qgscoordinatetransform.cpp b/src/core/qgscoordinatetransform.cpp
@@ -520,7 +520,7 @@ void QgsCoordinateTransform::transformInPlace(
 #endif //ANDROID
 
 
-QgsRectangle QgsCoordinateTransform::transformBoundingBox( const QgsRectangle rect, TransformDirection direction ) const
+QgsRectangle QgsCoordinateTransform::transformBoundingBox( const QgsRectangle rect, TransformDirection direction, const bool handle180Crossover ) const
 {
   // Calculate the bounding box of a QgsRectangle in the source CRS
   // when projected to the destination CRS (or the inverse).
@@ -592,8 +592,29 @@ QgsRectangle QgsCoordinateTransform::transformBoundingBox( const QgsRectangle re
 
   for ( int i = 0; i < numP * numP; i++ )
   {
-    if ( qIsFinite( x[i] ) && qIsFinite( y[i] ) )
+    if ( !qIsFinite( x[i] ) || !qIsFinite( y[i] ) )
+    {
+      continue;
+    }
+
+    if ( handle180Crossover )
+    {
+      //if crossing the date line, temporarily add 360 degrees to -ve longitudes
+      bb_rect.combineExtentWith( x[i] >= 0.0 ? x[i] : x[i] + 360.0, y[i] );
+    }
+    else
+    {
       bb_rect.combineExtentWith( x[i], y[i] );
+    }
+  }
+
+  if ( handle180Crossover )
+  {
+    //subtract temporary addition of 360 degrees from longitudes
+    if ( bb_rect.xMinimum() > 180.0 )
+      bb_rect.setXMinimum( bb_rect.xMinimum() - 360.0 );
+    if ( bb_rect.xMaximum() > 180.0 )
+      bb_rect.setXMaximum( bb_rect.xMaximum() - 360.0 );
   }
 
   QgsDebugMsg( "Projected extent: " + bb_rect.toString() );

diff --git a/src/core/qgscoordinatetransform.h b/src/core/qgscoordinatetransform.h
@@ -148,9 +148,11 @@ class CORE_EXPORT QgsCoordinateTransform : public QObject
      * returned rectangle.
      * @param theRect rect to transform
      * @param direction TransformDirection (defaults to ForwardTransform)
+     * @param handle180Crossover set to true if destination crs is geographic and handling of extents crossing the 180 degree
+     * longitude line is required
      * @return QgsRectangle in Destination Coordinate System
      */
-    QgsRectangle transformBoundingBox( const QgsRectangle theRect, TransformDirection direction = ForwardTransform ) const;
+    QgsRectangle transformBoundingBox( const QgsRectangle theRect, TransformDirection direction = ForwardTransform, const bool handle180Crossover = false ) const;
 
     // Same as for the other transform() functions, but alters the x
     // and y variables in place. The second one works with good old-fashioned

diff --git a/tests/src/core/CMakeLists.txt b/tests/src/core/CMakeLists.txt
@@ -98,6 +98,7 @@ ADD_QGIS_TEST(blendmodestest testqgsblendmodes.cpp)
 ADD_QGIS_TEST(geometrytest testqgsgeometry.cpp)
 ADD_QGIS_TEST(geometryimporttest testqgsgeometryimport.cpp)
 ADD_QGIS_TEST(coordinatereferencesystemtest testqgscoordinatereferencesystem.cpp)
+ADD_QGIS_TEST(coordinatetransformtest testqgscoordinatetransform.cpp)
 ADD_DEPENDENCIES(qgis_coordinatereferencesystemtest synccrsdb)
 ADD_QGIS_TEST(pointtest testqgspoint.cpp)
 ADD_QGIS_TEST(vectordataprovidertest testqgsvectordataprovider.cpp)

diff --git a/tests/src/core/testqgscoordinatetransform.cpp b/tests/src/core/testqgscoordinatetransform.cpp
@@ -0,0 +1,65 @@
+/***************************************************************************
+                         testqgscoordinatetransform.cpp
+                         -----------------------
+    begin                : October 2014
+    copyright            : (C) 2014 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+#include "qgscoordinatetransform.h"
+#include "qgsapplication.h"
+#include <QObject>
+#include <QtTest>
+
+class TestQgsCoordinateTransform: public QObject
+{
+    Q_OBJECT
+
+  private slots:
+    void initTestCase();
+    void transformBoundingBox();
+
+  private:
+
+};
+
+
+void TestQgsCoordinateTransform::initTestCase()
+{
+  QgsApplication::init();
+  QgsApplication::initQgis();
+
+}
+
+void TestQgsCoordinateTransform::transformBoundingBox()
+{
+  //test transforming a bounding box which crosses the 180 degree longitude line
+  QgsCoordinateReferenceSystem sourceSrs;
+  sourceSrs.createFromSrid( 3994 );
+  QgsCoordinateReferenceSystem destSrs;
+  destSrs.createFromSrid( 4326 );
+
+  QgsCoordinateTransform tr( sourceSrs, destSrs );
+  QgsRectangle crossingRect( 6374985, -3626584, 7021195, -3272435 );
+  QgsRectangle resultRect = tr.transformBoundingBox( crossingRect, QgsCoordinateTransform::ForwardTransform, true );
+  QgsRectangle expectedRect;
+  expectedRect.setXMinimum( 175.771 );
+  expectedRect.setYMinimum( -39.7222 );
+  expectedRect.setXMaximum( -176.549 );
+  expectedRect.setYMaximum( -36.3951 );
+  QVERIFY( qgsDoubleNear( resultRect.xMinimum(), expectedRect.xMinimum(), 0.001 ) );
+  QVERIFY( qgsDoubleNear( resultRect.yMinimum(), expectedRect.yMinimum(), 0.001 ) );
+  QVERIFY( qgsDoubleNear( resultRect.xMaximum(), expectedRect.xMaximum(), 0.001 ) );
+  QVERIFY( qgsDoubleNear( resultRect.yMaximum(), expectedRect.yMaximum(), 0.001 ) );
+}
+
+QTEST_MAIN( TestQgsCoordinateTransform )
+#include "moc_testqgscoordinatetransform.cxx"