Use screen dpi as reference dpi for computing wmts composer scale factor

Ref: 813f818caef896a0f3b3e0ebed8436803ee908e4
kadas-albireo · Dec 22, 2016 · 09a4cb0 · 09a4cb0
1 parent faa35ae
commit 09a4cb0
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/src/core/raster/qgsrasterdrawer.cpp b/src/core/raster/qgsrasterdrawer.cpp
@@ -49,7 +49,9 @@ void QgsRasterDrawer::draw( QPainter* p, QgsRasterViewPort* viewPort, const QgsM
 
   if ( ctx && ctx->customRenderFlags().split( ";" ).contains( "composer" ) && isWMTSLayer( mIterator->input() ) ) //wmts case, comply with standard pixel size of 0.28mm from specification
   {
-    scaleFactor = ( 1.0 / 0.28 * 25.4 ) / p->device()->logicalDpiX();
+    QImage image( 1, 1, QImage::Format_ARGB32 );
+    scaleFactor = double( image.logicalDpiX() ) / p->device()->logicalDpiX();
+    QgsDebugMsg( QString( "Scale factor: %1 (device DPI: %2)" ).arg( scaleFactor ).arg( p->device()->logicalDpiX() ) );
     width = width * scaleFactor;
     height = height * scaleFactor;
     mapToPixel.setParameters( ctx->extent().width() / width, ctx->extent().xMinimum(), ctx->extent().yMinimum(), height );