Merge pull request #4488 from nirvn/saveasimage_fix_rotated

Author: nirvn

src/app/qgisapp.cpp

@@ -5804,14 +5804,6 @@ void QgisApp::saveMapAsImage()
   QPair< QString, QString> myFileNameAndFilter = QgisGui::getSaveAsImageName( this, tr( "Choose a file name to save the map image as" ) );
   if ( myFileNameAndFilter.first != QLatin1String( "" ) )
   {
-    QSize size = mMapCanvas->size();
-    if ( dlg.extent() != mMapCanvas->extent() )
-    {
-      size.setWidth( mMapCanvas->size().width() * dlg.extent().width() / mMapCanvas->extent().width() );
-      size.setHeight( mMapCanvas->size().height() * dlg.extent().height() / mMapCanvas->extent().height() );
-    }
-    size *=  dlg.dpi() / qt_defaultDpiX();
-
     QgsMapSettings ms = QgsMapSettings();
     ms.setDestinationCrs( QgsProject::instance()->crs() );
     ms.setExtent( dlg.extent() );

src/app/qgsmapsavedialog.cpp

@@ -31,19 +31,23 @@ Q_GUI_EXPORT extern int qt_defaultDpiX();
 
 QgsMapSaveDialog::QgsMapSaveDialog( QWidget *parent, QgsMapCanvas *mapCanvas, const QString &activeDecorations )
   : QDialog( parent )
-  , mExtent( mapCanvas->mapSettings().visibleExtent() )
-  , mDpi( mapCanvas->mapSettings().outputDpi() )
-  , mSize( mapCanvas->mapSettings().outputSize() )
 {
   setupUi( this );
 
+  // Use unrotated visible extent to insure output size and scale matches canvas
+  QgsMapSettings ms = mapCanvas->mapSettings();
+  ms.setRotation( 0 );
+  mExtent = ms.visibleExtent();
+  mDpi = ms.outputDpi();
+  mSize = ms.outputSize();
+
   mResolutionSpinBox->setValue( qt_defaultDpiX() );
 
-  mExtentGroupBox->setOutputCrs( mapCanvas->mapSettings().destinationCrs() );
-  mExtentGroupBox->setCurrentExtent( mExtent, mapCanvas->mapSettings().destinationCrs() );
+  mExtentGroupBox->setOutputCrs( ms.destinationCrs() );
+  mExtentGroupBox->setCurrentExtent( mExtent, ms.destinationCrs() );
   mExtentGroupBox->setOutputExtentFromCurrent();
 
-  mScaleWidget->setScale( 1 / mapCanvas->mapSettings().scale() );
+  mScaleWidget->setScale( 1 / ms.scale() );
   mScaleWidget->setMapCanvas( mapCanvas );
   mScaleWidget->setShowCurrentScaleButton( true );
 

src/core/qgsmapsettingsutils.cpp

@@ -22,23 +22,60 @@
 
 QString QgsMapSettingsUtils::worldFileContent( const QgsMapSettings &mapSettings )
 {
-  double xOrigin = mapSettings.visiblePolygon().at( 0 ).x() + ( mapSettings.mapUnitsPerPixel() / 2 );
-  double yOrigin = mapSettings.visiblePolygon().at( 0 ).y() - ( mapSettings.mapUnitsPerPixel() / 2 );
+  QgsMapSettings ms = mapSettings;
+
+  double rotation = ms.rotation();
+  double alpha = rotation / 180 * M_PI;
+
+  // reset rotation to 0 to calculate world file parameters
+  ms.setRotation( 0 );
+
+  double xOrigin = ms.visibleExtent().xMinimum() + ( ms.mapUnitsPerPixel() / 2 );
+  double yOrigin = ms.visibleExtent().yMaximum() - ( ms.mapUnitsPerPixel() / 2 );
+
+  double xCenter = ms.visibleExtent().center().x();
+  double yCenter = ms.visibleExtent().center().y();
+
+  // scaling matrix
+  double s[6];
+  s[0] = ms.mapUnitsPerPixel();
+  s[1] = 0;
+  s[2] = xOrigin;
+  s[3] = 0;
+  s[4] = ms.mapUnitsPerPixel();
+  s[5] = yOrigin;
+
+  // rotation matrix
+  double r[6];
+  r[0] = cos( alpha );
+  r[1] = -sin( alpha );
+  r[2] = xCenter * ( 1 - cos( alpha ) ) + yCenter * sin( alpha );
+  r[3] = sin( alpha );
+  r[4] = cos( alpha );
+  r[5] = - xCenter * sin( alpha ) + yCenter * ( 1 - cos( alpha ) );
+
+  // result = rotation x scaling = rotation(scaling(X))
+  double a = r[0] * s[0] + r[1] * s[3];
+  double b = r[0] * s[1] + r[1] * s[4];
+  double c = r[0] * s[2] + r[1] * s[5] + r[2];
+  double d = r[3] * s[0] + r[4] * s[3];
+  double e = r[3] * s[1] + r[4] * s[4];
+  double f = r[3] * s[2] + r[4] * s[5] + r[5];
 
   QString content;
   // Pixel XDim
-  content += qgsDoubleToString( mapSettings.mapUnitsPerPixel() ) + "\r\n";
+  content += qgsDoubleToString( a ) + "\r\n";
   // Rotation on y axis
-  content += QString( "%1\r\n" ).arg( mapSettings.rotation() );
+  content += qgsDoubleToString( d ) + "\r\n";
   // Rotation on x axis
-  content += QString( "%1\r\n" ).arg( mapSettings.rotation() );
+  content += qgsDoubleToString( -b ) + "\r\n";
   // Pixel YDim - almost always negative
   // See https://en.wikipedia.org/wiki/World_file#cite_ref-3
-  content += '-' + qgsDoubleToString( mapSettings.mapUnitsPerPixel() ) + "\r\n";
+  content += "-" + qgsDoubleToString( e ) + "\r\n";
   // Origin X (center of top left cell)
-  content += qgsDoubleToString( xOrigin ) + "\r\n";
+  content += qgsDoubleToString( c ) + "\r\n";
   // Origin Y (center of top left cell)
-  content += qgsDoubleToString( yOrigin ) + "\r\n";
+  content += qgsDoubleToString( f ) + "\r\n";
 
   return content;
 }

tests/src/core/testqgsmapsettingsutils.cpp

@@ -43,11 +43,15 @@ class TestQgsMapSettingsUtils : public QObject
 void TestQgsMapSettingsUtils::initTestCase()
 {
   mMapSettings.setExtent( QgsRectangle( 0, 0, 1, 1 ) );
+  mMapSettings.setOutputSize( QSize( 1, 1 ) );
 }
 
 void TestQgsMapSettingsUtils::createWorldFileContent()
 {
   QCOMPARE( QgsMapSettingsUtils::worldFileContent( mMapSettings ), QString( "1\r\n0\r\n0\r\n-1\r\n0.5\r\n0.5\r\n" ) );
+
+  mMapSettings.setRotation( 45 );
+  QCOMPARE( QgsMapSettingsUtils::worldFileContent( mMapSettings ), QString( "0.70710678118654757\r\n0.70710678118654746\r\n0.70710678118654746\r\n-0.70710678118654757\r\n0.5\r\n0.49999999999999994\r\n" ) );
 }
 
 QGSTEST_MAIN( TestQgsMapSettingsUtils )