For xyz/mapserver tiles, disable smooth pixmap transform when

we are rendering at native tile resolutions (or just close enough to) This allows pixel-perfect rendering of tiles at native resolutions
qgis · Jun 7, 2019 · 1c9586a · 1c9586a
1 parent 493b17c
commit 1c9586a
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Showing 4 changed files with 23 additions and 9 deletions.
diff --git a/src/providers/arcgisrest/qgsamsprovider.cpp b/src/providers/arcgisrest/qgsamsprovider.cpp
@@ -536,7 +536,9 @@ QImage QgsAmsProvider::draw( const QgsRectangle &viewExtent, int pixelWidth, int
       QImage localImage;
       if ( QgsTileCache::tile( r.url, localImage ) )
       {
-        tileImages << TileImage( r.rect, localImage );
+        // if image size is "close enough" to destination size, don't smooth it out. Instead try for pixel-perfect placement!
+        bool disableSmoothing = ( qgsDoubleNear( r.rect.width(), tileWidth, 2 ) && qgsDoubleNear( r.rect.height(), tileHeight, 2 ) );
+        tileImages << TileImage( r.rect, localImage, !disableSmoothing );
       }
       else
       {
@@ -556,6 +558,7 @@ QImage QgsAmsProvider::draw( const QgsRectangle &viewExtent, int pixelWidth, int
       // from lower or higher resolution available to give the user a bit of context
       // while loading the right resolution
       p.setCompositionMode( QPainter::CompositionMode_Source );
+      p.setRenderHint( QPainter::SmoothPixmapTransform, false );  // let's not waste time with bilinear filtering
 
       auto fetchOtherResTiles = [&getRequests]( int otherLevel, QList< TileImage> &otherResTiles, QList< QRectF > &missingRects )
       {
@@ -568,7 +571,7 @@ QImage QgsAmsProvider::draw( const QgsRectangle &viewExtent, int pixelWidth, int
           if ( ! QgsTileCache::tile( r.url, localImage ) )
             continue;
 
-          otherResTiles << TileImage( r.rect, localImage );
+          otherResTiles << TileImage( r.rect, localImage, false );
 
           // see if there are any missing rects that are completely covered by this tile
           for ( const QRectF &missingRect : qgis::as_const( missingRects ) )
@@ -619,6 +622,8 @@ QImage QgsAmsProvider::draw( const QgsRectangle &viewExtent, int pixelWidth, int
     // draw composite in this resolution
     for ( const TileImage &ti : qgis::as_const( tileImages ) )
     {
+      if ( ti.smooth )
+        p.setRenderHint( QPainter::SmoothPixmapTransform, true );
       p.drawImage( ti.rect, ti.img );
     }
 
@@ -1048,6 +1053,10 @@ void QgsAmsTiledImageDownloadHandler::tileReplyFinished()
       if ( !myLocalImage.isNull() )
       {
         QPainter p( mImage );
+        // if image size is "close enough" to destination size, don't smooth it out. Instead try for pixel-perfect placement!
+        const bool disableSmoothing = ( qgsDoubleNear( r.width(), myLocalImage.width(), 2 ) && qgsDoubleNear( r.height(), myLocalImage.height(), 2 ) );
+        if ( !disableSmoothing )
+          p.setRenderHint( QPainter::SmoothPixmapTransform, true );
         p.drawImage( r, myLocalImage );
         p.end();
 

diff --git a/src/providers/arcgisrest/qgsamsprovider.h b/src/providers/arcgisrest/qgsamsprovider.h
@@ -113,9 +113,10 @@ class QgsAmsProvider : public QgsRasterDataProvider
     //! Helper structure to store a cached tile image with its rectangle
     typedef struct TileImage
     {
-      TileImage( const QRectF &r, const QImage &i ): rect( r ), img( i ) {}
+      TileImage( const QRectF &r, const QImage &i, bool smooth ): rect( r ), img( i ), smooth( smooth ) {}
       QRectF rect; //!< Destination rectangle for a tile (in screen coordinates)
       QImage img;  //!< Cached tile to be drawn
+      bool smooth;
     } TileImage;
 
   protected:

diff --git a/src/providers/wms/qgswmsprovider.cpp b/src/providers/wms/qgswmsprovider.cpp
@@ -565,7 +565,7 @@ void QgsWmsProvider::fetchOtherResTiles( QgsTileMode tileMode, const QgsRectangl
                 ( viewExtent.yMaximum() - r.rect.bottom() ) / cr,
                 r.rect.width() / cr,
                 r.rect.height() / cr );
-    otherResTiles << TileImage( dst, localImage );
+    otherResTiles << TileImage( dst, localImage, false );
 
     // see if there are any missing rects that are completely covered by this tile
     const auto constMissingRects = missingRects;
@@ -782,12 +782,13 @@ QImage *QgsWmsProvider::draw( QgsRectangle const &viewExtent, int pixelWidth, in
       if ( QgsTileCache::tile( r.url, localImage ) )
       {
         double cr = viewExtent.width() / image->width();
-
         QRectF dst( ( r.rect.left() - viewExtent.xMinimum() ) / cr,
                     ( viewExtent.yMaximum() - r.rect.bottom() ) / cr,
                     r.rect.width() / cr,
                     r.rect.height() / cr );
-        tileImages << TileImage( dst, localImage );
+        // if image size is "close enough" to destination size, don't smooth it out. Instead try for pixel-perfect placement!
+        bool disableSmoothing = ( qgsDoubleNear( dst.width(), tm->tileWidth, 2 ) && qgsDoubleNear( dst.height(), tm->tileHeight, 2 ) );
+        tileImages << TileImage( dst, localImage, !disableSmoothing );
       }
       else
       {
@@ -849,7 +850,7 @@ QImage *QgsWmsProvider::draw( QgsRectangle const &viewExtent, int pixelWidth, in
     const auto constTileImages = tileImages;
     for ( const TileImage &ti : constTileImages )
     {
-      if ( mSettings.mSmoothPixmapTransform )
+      if ( ti.smooth && mSettings.mSmoothPixmapTransform )
         p.setRenderHint( QPainter::SmoothPixmapTransform, true );
       p.drawImage( ti.rect, ti.img );
 
@@ -3949,7 +3950,9 @@ void QgsWmsTiledImageDownloadHandler::tileReplyFinished()
       if ( !myLocalImage.isNull() )
       {
         QPainter p( mImage );
-        if ( mSmoothPixmapTransform )
+        // if image size is "close enough" to destination size, don't smooth it out. Instead try for pixel-perfect placement!
+        const bool disableSmoothing = ( qgsDoubleNear( dst.width(), myLocalImage.width(), 2 ) && qgsDoubleNear( dst.height(), myLocalImage.height(), 2 ) );
+        if ( !disableSmoothing && mSmoothPixmapTransform )
           p.setRenderHint( QPainter::SmoothPixmapTransform, true );
         p.drawImage( dst, myLocalImage );
         p.end();

diff --git a/src/providers/wms/qgswmsprovider.h b/src/providers/wms/qgswmsprovider.h
@@ -336,9 +336,10 @@ class QgsWmsProvider : public QgsRasterDataProvider
     //! Helper structure to store a cached tile image with its rectangle
     typedef struct TileImage
     {
-      TileImage( const QRectF &r, const QImage &i ): rect( r ), img( i ) {}
+      TileImage( const QRectF &r, const QImage &i, bool smooth ): rect( r ), img( i ), smooth( smooth ) {}
       QRectF rect; //!< Destination rectangle for a tile (in screen coordinates)
       QImage img;  //!< Cached tile to be drawn
+      bool smooth; //!< Whether to use antialiasing/smooth transforms when rendering tile
     } TileImage;
     //! Gets tiles from a different resolution to cover the missing areas
     void fetchOtherResTiles( QgsTileMode tileMode, const QgsRectangle &viewExtent, int imageWidth, QList<QRectF> &missing, double tres, int resOffset, QList<TileImage> &otherResTiles );