Expose antialiasing option in image export dialog

Allows for creating non-antialiased images from layouts. Note that
some layout item types do not correctly respect this setting, but
at least map items do and the API is in place for them to be
fixed later.

Fixes #9281

python/core/layout/qgslayoutexporter.sip

@@ -95,6 +95,11 @@ to render sections of pages rather than full pages.
 
     struct ImageExportSettings
     {
+      ImageExportSettings();
+%Docstring
+Constructor for ImageExportSettings
+%End
+
       double dpi;
 %Docstring
 Resolution to export layout at
@@ -141,6 +146,11 @@ Resolution to export layout at
  exported images.
 %End
 
+      QgsLayoutContext::Flags flags;
+%Docstring
+ Layout context flags, which control how the export will be created.
+%End
+
     };
 
     ExportResult exportToImage( const QString &filePath, const ImageExportSettings &settings );

src/app/layout/qgslayoutdesignerdialog.cpp

@@ -1450,13 +1450,15 @@ void QgsLayoutDesignerDialog::exportToRaster()
   int marginRight = mLayout->customProperty( QStringLiteral( "imageCropMarginRight" ), 0 ).toInt();
   int marginBottom = mLayout->customProperty( QStringLiteral( "imageCropMarginBottom" ), 0 ).toInt();
   int marginLeft = mLayout->customProperty( QStringLiteral( "imageCropMarginLeft" ), 0 ).toInt();
+  bool antialias = mLayout->customProperty( QStringLiteral( "imageAntialias" ), true ).toBool();
 
   QgsLayoutImageExportOptionsDialog imageDlg( this );
   imageDlg.setImageSize( maxPageSize );
   imageDlg.setResolution( dpi );
   imageDlg.setCropToContents( cropToContents );
   imageDlg.setCropMargins( marginTop, marginRight, marginBottom, marginLeft );
   imageDlg.setGenerateWorldFile( mLayout->customProperty( QStringLiteral( "exportWorldFile" ), false ).toBool() );
+  imageDlg.setAntialiasing( antialias );
 
 #if 0 //TODO
   QgsAtlasComposition *atlasMap = &mComposition->atlasComposition();
@@ -1494,6 +1496,8 @@ void QgsLayoutDesignerDialog::exportToRaster()
   mLayout->setCustomProperty( QStringLiteral( "imageCropMarginBottom" ), marginBottom );
   mLayout->setCustomProperty( QStringLiteral( "imageCropMarginLeft" ), marginLeft );
 
+  mLayout->setCustomProperty( QStringLiteral( "imageAntialias" ), imageDlg.antialiasing() );
+
   mView->setPaintingEnabled( false );
 
   QgsLayoutExporter exporter( mLayout );
@@ -1507,6 +1511,9 @@ void QgsLayoutDesignerDialog::exportToRaster()
     settings.imageSize = QSize( imageDlg.imageWidth(), imageDlg.imageHeight() );
   }
   settings.generateWorldFile = imageDlg.generateWorldFile();
+  settings.flags = QgsLayoutContext::FlagUseAdvancedEffects;
+  if ( imageDlg.antialiasing() )
+    settings.flags |= QgsLayoutContext::FlagAntialiasing;
 
   switch ( exporter.exportToImage( fileNExt.first, settings ) )
   {

src/app/layout/qgslayoutimageexportoptionsdialog.cpp

@@ -105,6 +105,16 @@ bool QgsLayoutImageExportOptionsDialog::generateWorldFile() const
   return mGenerateWorldFile->isChecked();
 }
 
+void QgsLayoutImageExportOptionsDialog::setAntialiasing( bool antialias )
+{
+  mAntialiasingCheckBox->setChecked( antialias );
+}
+
+bool QgsLayoutImageExportOptionsDialog::antialiasing() const
+{
+  return mAntialiasingCheckBox->isChecked();
+}
+
 void QgsLayoutImageExportOptionsDialog::getCropMargins( int &topMargin, int &rightMargin, int &bottomMargin, int &leftMargin ) const
 {
   topMargin = mTopMarginSpinBox->value();

src/app/layout/qgslayoutimageexportoptionsdialog.h

@@ -96,6 +96,18 @@ class QgsLayoutImageExportOptionsDialog: public QDialog, private Ui::QgsLayoutIm
      */
     bool generateWorldFile() const;
 
+    /**
+     * Sets whether antialiasing should be used in the export.
+     * \see antialiasing()
+     */
+    void setAntialiasing( bool antialias );
+
+    /**
+     * Returns whether antialiasing should be used in the export.
+     * \see setAntialiasing()
+     */
+    bool antialiasing() const;
+
     /**
      * Fetches the current crop to contents margin values, in pixels.
      * \param topMargin destination for top margin

src/core/layout/qgslayoutexporter.cpp

@@ -85,6 +85,8 @@ void QgsLayoutExporter::renderRegion( QPainter *painter, const QRectF &region )
   setSnapLinesVisible( false );
 #endif
 
+  painter->setRenderHint( QPainter::Antialiasing, mLayout->context().flags() & QgsLayoutContext::FlagAntialiasing );
+
   mLayout->render( painter, QRectF( 0, 0, paintDevice->width(), paintDevice->height() ), region );
 
 #if 0 // TODO
@@ -132,24 +134,27 @@ QImage QgsLayoutExporter::renderRegionToImage( const QRectF &region, QSize image
 }
 
 ///@cond PRIVATE
-class LayoutDpiRestorer
+class LayoutContextSettingsRestorer
 {
   public:
 
-    LayoutDpiRestorer( QgsLayout *layout )
+    LayoutContextSettingsRestorer( QgsLayout *layout )
       : mLayout( layout )
-      , mPreviousSetting( layout->context().dpi() )
+      , mPreviousDpi( layout->context().dpi() )
+      , mPreviousFlags( layout->context().flags() )
     {
     }
 
-    ~LayoutDpiRestorer()
+    ~LayoutContextSettingsRestorer()
     {
-      mLayout->context().setDpi( mPreviousSetting );
+      mLayout->context().setDpi( mPreviousDpi );
+      mLayout->context().setFlags( mPreviousFlags );
     }
 
   private:
     QgsLayout *mLayout = nullptr;
-    double mPreviousSetting = 0;
+    double mPreviousDpi = 0;
+    QgsLayoutContext::Flags mPreviousFlags = 0;
 };
 ///@endcond PRIVATE
 
@@ -168,9 +173,10 @@ QgsLayoutExporter::ExportResult QgsLayoutExporter::exportToImage( const QString
   QString baseName = fi.baseName();
   QString extension = fi.completeSuffix();
 
-  LayoutDpiRestorer dpiRestorer( mLayout );
+  LayoutContextSettingsRestorer dpiRestorer( mLayout );
   ( void )dpiRestorer;
   mLayout->context().setDpi( settings.dpi );
+  mLayout->context().setFlags( settings.flags );
 
   QList< int > pages;
   if ( settings.pages.empty() )

src/core/layout/qgslayoutexporter.h

@@ -18,6 +18,7 @@
 
 #include "qgis_core.h"
 #include "qgsmargins.h"
+#include "qgslayoutcontext.h"
 #include <QPointer>
 #include <QSize>
 #include <QRectF>
@@ -111,6 +112,11 @@ class CORE_EXPORT QgsLayoutExporter
     //! Contains settings relating to exporting layouts to raster images
     struct ImageExportSettings
     {
+      //! Constructor for ImageExportSettings
+      ImageExportSettings()
+        : flags( QgsLayoutContext::FlagAntialiasing | QgsLayoutContext::FlagUseAdvancedEffects )
+      {}
+
       //! Resolution to export layout at
       double dpi;
 
@@ -155,6 +161,11 @@ class CORE_EXPORT QgsLayoutExporter
        */
       bool generateWorldFile = false;
 
+      /**
+       * Layout context flags, which control how the export will be created.
+       */
+      QgsLayoutContext::Flags flags = 0;
+
     };
 
     /**

src/core/layout/qgslayoutitemmap.cpp

@@ -990,7 +990,7 @@ QgsMapSettings QgsLayoutItemMap::mapSettings( const QgsRectangle &extent, QSizeF
 
   // layout-specific overrides of flags
   jobMapSettings.setFlag( QgsMapSettings::ForceVectorOutput, true ); // force vector output (no caching of marker images etc.)
-  jobMapSettings.setFlag( QgsMapSettings::Antialiasing, true );
+  jobMapSettings.setFlag( QgsMapSettings::Antialiasing, mLayout->context().flags() & QgsLayoutContext::FlagAntialiasing );
   jobMapSettings.setFlag( QgsMapSettings::DrawEditingInfo, false );
   jobMapSettings.setFlag( QgsMapSettings::DrawSelection, false );
   jobMapSettings.setFlag( QgsMapSettings::UseAdvancedEffects, mLayout->context().flags() & QgsLayoutContext::FlagUseAdvancedEffects );

src/ui/layout/qgslayoutimageexportoptions.ui

@@ -244,6 +244,16 @@
      </property>
     </widget>
    </item>
+   <item>
+    <widget class="QCheckBox" name="mAntialiasingCheckBox">
+     <property name="toolTip">
+      <string>If unchecked, the generated images will not be antialiased</string>
+     </property>
+     <property name="text">
+      <string>Enable antialiasing</string>
+     </property>
+    </widget>
+   </item>
    <item>
     <spacer name="verticalSpacer">
      <property name="orientation">