At the composition stage of the second pass introduced with selective…

… masking, the unmasked elements located under the mask are copied into a temporary image buffer and then readded later to the final image. This copy was done using the masks from selective masking with their full opacity informations. Unmasked informations were thus combined with opacity from the mask leading to the introduction of several artefacts : * The "phantom lines" #34650 (opacity information introduced by the antialising on mask drawing) * Opacity applied on non masked surfaces in #34947 To fix this issue a temporary mask is created for the copy of unmasked pixels, in this temporary mask the alpha channel is "binarized" (fully opaque on masking pixel, fully transparent on non masking pixel). Should fix #34650 and fix #34947
qgis · Jun 7, 2020 · 708910a · 708910a
1 parent 76f53d2
commit 708910a
Showing 1 changed file with 10 additions and 1 deletion.
diff --git a/src/core/qgsmaprendererjob.cpp b/src/core/qgsmaprendererjob.cpp
@@ -817,7 +817,16 @@ void QgsMapRendererJob::composeSecondPass( LayerRenderJobs &secondPassJobs, Labe
       // Only retain parts of the second rendering that are "inside" the mask image
       QPainter *painter = job.context.painter();
       painter->setCompositionMode( QPainter::CompositionMode_DestinationIn );
-      painter->drawImage( 0, 0, *maskImage );
+      QImage maskBinAlpha( *maskImage );
+      QRgb *pdata = ( QRgb * )maskBinAlpha.bits();
+      for ( int i = 0; i < maskBinAlpha.width() * maskBinAlpha.height(); ++i )
+      {
+        pdata[i] = qRgba( qRed( pdata[i] ),
+                          qGreen( pdata[i] ),
+                          qBlue( pdata[i] ),
+                          qAlpha( pdata[i] ) > 0 ? 255 : 0 );
+      }
+      painter->drawImage( 0, 0, maskBinAlpha );
 #if DEBUG_RENDERING
       job.img->save( QString( "/tmp/second_%1_a.png" ).arg( i ) );
 #endif