Fix inconcequent use of DPI at generating the WMS legend

- Consider DPI of QgsWmsRenderContext what is the OGC default (0.28 mm per pixel) or the passed WMS parameter - this is done by creating the QgsRenderContext by the mapSettings (with BBOX) or applying the dotsPerMm to the scaleFactor. - Additionally the image size needs to be calculated according to the QgsRenderContext now, what means it needs to be generated before. - The QPainter needs to be applied after to the context (since it's not passed by creating the context anymore).
qgis · Apr 1, 2023 · f926eb4 · f926eb4
1 parent 50adba3
commit f926eb4
Showing 1 changed file with 27 additions and 9 deletions.
diff --git a/src/server/services/wms/qgswmsrenderer.cpp b/src/server/services/wms/qgswmsrenderer.cpp
@@ -132,27 +132,45 @@ namespace QgsWms
     QgsLegendSettings settings = legendSettings();
     QgsLegendRenderer renderer( &model, settings );
 
-    // create image
+    // create context
+    QgsRenderContext context;
+    if ( !mWmsParameters.bbox().isEmpty() )
+    {
+      QgsMapSettings mapSettings;
+      mapSettings.setFlag( Qgis::MapSettingsFlag::RenderBlocking );
+      std::unique_ptr<QImage> tmp( createImage( mContext.mapSize( false ) ) );
+      configureMapSettings( tmp.get(), mapSettings );
+      context = QgsRenderContext::fromMapSettings( mapSettings );
+    }
+    else
+    {
+      context.setScaleFactor( mContext.dotsPerMm() );
+      const double mmPerMapUnit = 1 / QgsServerProjectUtils::wmsDefaultMapUnitsPerMm( *mProject );
+      context.setMapToPixel( QgsMapToPixel( 1 / ( mmPerMapUnit * context.scaleFactor() ) ) );
+    }
+
+    // create image according to context
     std::unique_ptr<QImage> image;
     const qreal dpmm = mContext.dotsPerMm();
-    const QSizeF minSize = renderer.minimumSize();
+    const QSizeF minSize = renderer.minimumSize( &context );
     const QSize size( static_cast<int>( minSize.width() * dpmm ), static_cast<int>( minSize.height() * dpmm ) );
     if ( !mContext.isValidWidthHeight( size.width(), size.height() ) )
     {
       throw QgsServerException( QStringLiteral( "Legend image is too large" ) );
     }
     image.reset( createImage( size ) );
 
-    // configure painter
+    // configure painter and addapt to the context
     QPainter painter( image.get() );
-    QgsRenderContext context = QgsRenderContext::fromQPainter( &painter );
+
+    context.setPainter( &painter );
+    if ( painter.renderHints() & QPainter::SmoothPixmapTransform )
+      context.setFlag( Qgis::RenderContextFlag::HighQualityImageTransforms, true );
+    if ( painter.renderHints() & QPainter::LosslessImageRendering )
+      context.setFlag( Qgis::RenderContextFlag::LosslessImageRendering, true );
+
     context.setFlag( Qgis::RenderContextFlag::Antialiasing, true );
     QgsScopedRenderContextScaleToMm scaleContext( context );
-    // QGIS 4.0 -- take from real render context instead
-    Q_NOWARN_DEPRECATED_PUSH
-    context.setRendererScale( settings.mapScale() );
-    context.setMapToPixel( QgsMapToPixel( 1 / ( settings.mmPerMapUnit() * context.scaleFactor() ) ) );
-    Q_NOWARN_DEPRECATED_POP
 
     // rendering
     renderer.drawLegend( context );