Raster rendering: enable provider-side resampling when available, and reprojection is done

python/plugins/processing/tests/testdata/expected/raster_zonal_stats_reproj.csv

@@ -1,5 +1,5 @@
 zone,deg2,sum,count,min,max,mean
-6.00000000,0.00034585,5378373.70841217,"34585",85.50000000,243.00000000,155.51174522
-4.00000000,0.00013848,1266379.78169250,"13848",86.30000305,93.90000153,91.44856887
-3.00000000,0.00026132,4379265.06565094,"26132",111.69999695,232.43850708,167.58246845
-1.00000000,0.00037290,4677866.67560577,"37290",85.00000000,219.19999695,125.44560675
+6.00000000,0.00034577,5379991.47400665,"34577",85.50000000,243.00000000,155.59451294
+4.00000000,0.00013913,1272219.50825500,"13913",86.30000305,93.90000153,91.44106291
+3.00000000,0.00026070,4368361.01625824,"26070",111.69999695,232.43850708,167.56275475
+1.00000000,0.00037291,4680372.30075836,"37291",85.00000000,219.19999695,125.50943393

python/plugins/processing/tests/testdata/expected/raster_zonal_stats_zone_crs_ref.csv

@@ -1,5 +1,5 @@
 zone,m2,sum,count,min,max,mean
-6.00000000,3055987.38515208,6069863.29187775,"39025",85.50000000,243.00000000,155.53781658
-4.00000000,1226310.37671958,1432050.30903625,"15660",86.30000305,93.90000153,91.44637989
-3.00000000,2310490.91092664,4944274.10529327,"29505",111.69999695,232.43850708,167.57410965
-1.00000000,3297568.96319678,5283155.23725128,"42110",85.00000000,219.19999695,125.46082254
+6.00000000,3055987.38515208,6070816.17861176,"39025",85.50000000,243.00000000,155.56223392
+4.00000000,1226310.37671958,1431734.66448212,"15660",86.30000305,93.90000153,91.42622379
+3.00000000,2310490.91092664,4941275.88129425,"29505",111.69999695,231.73440552,167.47249216
+1.00000000,3297568.96319678,5287336.89630127,"42110",85.00000000,219.19999695,125.56012577

python/plugins/processing/tests/testdata/qgis_algorithm_tests4.yaml

@@ -1773,7 +1773,7 @@ tests:
         type: raster
     results:
       OUTPUT:
-        hash: cdf6edb6afcefc5e80d60fa213df17aae59423019240807f5a49b72d
+        hash: 9c7f3070ad53b98ad9f42c3f758546268000043e990fbb38495d3c86
         type: rasterhash
 
   - algorithm: native:rasterbooleanand
@@ -1819,7 +1819,7 @@ tests:
         type: raster
     results:
       OUTPUT:
-        hash: dfe0bfc934a9d2a8ab865ad77db4278067830ac8e6f0470a730ad434
+        hash: eb41f92cb1198f1e4bed71e4a78d4fe2d3b35462a3949588d85cc818
         type: rasterhash
 
   - algorithm: native:rasterlogicalor
@@ -1888,7 +1888,7 @@ tests:
         type: raster
     results:
       OUTPUT:
-        hash: 56c4396468098a6f421e14682e22bb9cbb14027ed97f99cb8f85f953
+        hash: 2cd2f073cf337264140c1e5e3f162d5d134a731a094f1e1109e3ce12
         type: rasterhash
 
   - algorithm: native:rasterlogicalor
@@ -1911,7 +1911,7 @@ tests:
         type: raster
     results:
       OUTPUT:
-        hash: f8f7a412274c3133aee7fc24e3e6df2ddb52c6bc82663dd25154d3be
+        hash: d344a9306b7453c3faaef4558a9187da5525b0c90c6a04502bf15f1b
         type: rasterhash
 
   - algorithm: native:rasterlogicalor
@@ -1934,7 +1934,7 @@ tests:
         type: raster
     results:
       OUTPUT:
-        hash: 6c09e13126e16a267e36c79b0eeba7761422da7bd0387125f4c823e6
+        hash: 4e395a2151aba7558efedd43a33c85bbaae451ebcccef9a6dac86de4
         type: rasterhash
 
   - algorithm: native:addxyfields

src/core/raster/qgsrasterlayer.cpp

@@ -269,11 +269,22 @@ void QgsRasterLayer::draw( QPainter *theQPainter,
   //
 
   QgsRasterProjector *projector = mPipe.projector();
-
+  bool restoreOldResamplingStage = false;
+  QgsRasterPipe::ResamplingStage oldResamplingState = resamplingStage();
   // TODO add a method to interface to get provider and get provider
   // params in QgsRasterProjector
+
   if ( projector )
   {
+    // Force provider resampling if reprojection is needed
+    if ( mDataProvider != nullptr &&
+         ( mDataProvider->providerCapabilities() & QgsRasterDataProvider::ProviderHintCanPerformProviderResampling ) &&
+         rasterViewPort->mSrcCRS != rasterViewPort->mDestCRS &&
+         oldResamplingState != QgsRasterPipe::ResamplingStage::Provider )
+    {
+      restoreOldResamplingStage = true;
+      setResamplingStage( QgsRasterPipe::ResamplingStage::Provider );
+    }
     projector->setCrs( rasterViewPort->mSrcCRS, rasterViewPort->mDestCRS, rasterViewPort->mTransformContext );
   }
 
@@ -282,6 +293,11 @@ void QgsRasterLayer::draw( QPainter *theQPainter,
   QgsRasterDrawer drawer( &iterator );
   drawer.draw( theQPainter, rasterViewPort, qgsMapToPixel );
 
+  if ( restoreOldResamplingStage )
+  {
+    setResamplingStage( oldResamplingState );
+  }
+
   QgsDebugMsgLevel( QStringLiteral( "total raster draw time (ms):     %1" ).arg( time.elapsed(), 5 ), 4 );
 } //end of draw method
 

src/core/raster/qgsrasterlayerrenderer.cpp

@@ -281,11 +281,21 @@ bool QgsRasterLayerRenderer::render()
   //
 
   QgsRasterProjector *projector = mPipe->projector();
+  bool restoreOldResamplingStage = false;
+  QgsRasterPipe::ResamplingStage oldResamplingState = mPipe->resamplingStage();
 
   // TODO add a method to interface to get provider and get provider
   // params in QgsRasterProjector
   if ( projector )
   {
+    // Force provider resampling if reprojection is needed
+    if ( ( mPipe->provider()->providerCapabilities() & QgsRasterDataProvider::ProviderHintCanPerformProviderResampling ) &&
+         mRasterViewPort->mSrcCRS != mRasterViewPort->mDestCRS &&
+         oldResamplingState != QgsRasterPipe::ResamplingStage::Provider )
+    {
+      restoreOldResamplingStage = true;
+      mPipe->setResamplingStage( QgsRasterPipe::ResamplingStage::Provider );
+    }
     projector->setCrs( mRasterViewPort->mSrcCRS, mRasterViewPort->mDestCRS, mRasterViewPort->mTransformContext );
   }
 
@@ -294,6 +304,11 @@ bool QgsRasterLayerRenderer::render()
   QgsRasterDrawer drawer( &iterator );
   drawer.draw( renderContext()->painter(), mRasterViewPort, &renderContext()->mapToPixel(), mFeedback );
 
+  if ( restoreOldResamplingStage )
+  {
+    mPipe->setResamplingStage( oldResamplingState );
+  }
+
   const QStringList errors = mFeedback->errors();
   for ( const QString &error : errors )
   {

src/core/raster/qgsrasterprojector.cpp

@@ -119,11 +119,12 @@ ProjectorData::ProjectorData( const QgsRectangle &extent, int width, int height,
     QgsRasterDataProvider *provider = dynamic_cast<QgsRasterDataProvider *>( input->sourceInput() );
     if ( provider )
     {
-      // If provider-side resampling is enabled, we will get a much better looking
+      // If provider-side resampling is possible, we will get a much better looking
       // result by not requesting at the maximum resolution and then doing nearest
       // resampling here. A real fix would be to do resampling during reprojection
       // however.
-      if ( !provider->isProviderResamplingEnabled() && ( provider->capabilities() & QgsRasterDataProvider::Size ) )
+      if ( !( provider->providerCapabilities() & QgsRasterDataProvider::ProviderHintCanPerformProviderResampling ) &&
+           ( provider->capabilities() & QgsRasterDataProvider::Size ) )
       {
         mMaxSrcXRes = provider->extent().width() / provider->xSize();
         mMaxSrcYRes = provider->extent().height() / provider->ySize();