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Fix rendering artifacts on the edges of resampled raster tiles

Browse Source 
We now buffer the request for the input to a resample filter by
a variable number of pixels (depending on the resampling type)
in order to fetch the neighbouring pixels to the edges of individual
raster blocks. This allows the resampling to utilise these
neighbouring pixels when resampling the edges of tiles, avoiding
discrepancies and rendering artifacts over the borders of
raster tiles.

Fixes #30152
This commit is contained in:
Nyall Dawson 2019-11-08 17:38:58 +10:00
parent 7fdac2fc6b
commit 41fa4b19fd
11 changed files with 240 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
python/core/auto_generated/raster/qgsbilinearrasterresampler.sip.in
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@ -35,6 +35,8 @@ Constructor for QgsBilinearRasterResampler.
virtual QgsBilinearRasterResampler *clone() const /Factory/;
virtual int tileBufferPixels() const;
};
/************************************************************************

2
python/core/auto_generated/raster/qgscubicrasterresampler.sip.in
View File

@ -34,6 +34,8 @@ Constructor for QgsCubicRasterResampler.
virtual QString type() const;
virtual int tileBufferPixels() const;
};
/************************************************************************

9
python/core/auto_generated/raster/qgsrasterresampler.sip.in
View File

@ -54,6 +54,15 @@ Needs to be implemented by subclasses.
Gets a deep copy of this object.
Needs to be reimplemented by subclasses.
Ownership is transferred to the caller.
%End
virtual int tileBufferPixels() const;
%Docstring
Returns the optional tile buffer size in pixels. This represents
the size to buffer individual resampled tile requests prior to resampling,
in order to avoid rendering artifacts at the edges of raster tile boundaries.
.. versionadded:: 3.10.1
%End
};

5
src/core/raster/qgsbilinearrasterresampler.cpp
View File

@ -25,6 +25,11 @@ QgsBilinearRasterResampler *QgsBilinearRasterResampler::clone() const
return new QgsBilinearRasterResampler();
}
int QgsBilinearRasterResampler::tileBufferPixels() const
{
return 1;
}
Q_NOWARN_DEPRECATED_PUSH
void QgsBilinearRasterResampler::resample( const QImage &srcImage, QImage &dstImage )
{

1
src/core/raster/qgsbilinearrasterresampler.h
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@ -43,6 +43,7 @@ class CORE_EXPORT QgsBilinearRasterResampler: public QgsRasterResamplerV2
QImage resampleV2( const QImage &source, const QSize &size ) override;
QString type() const override;
QgsBilinearRasterResampler *clone() const override SIP_FACTORY;
int tileBufferPixels() const override;
};
#endif // QGSBILINEARRASTERRESAMPLER_H

5
src/core/raster/qgscubicrasterresampler.cpp
View File

@ -42,3 +42,8 @@ QString QgsCubicRasterResampler::type() const
return QStringLiteral( "cubic" );
}
int QgsCubicRasterResampler::tileBufferPixels() const
{
return 2;
}

1
src/core/raster/qgscubicrasterresampler.h
View File

@ -42,6 +42,7 @@ class CORE_EXPORT QgsCubicRasterResampler: public QgsRasterResamplerV2
QImage resampleV2( const QImage &source, const QSize &size ) override;
Q_DECL_DEPRECATED void resample( const QImage &srcImage, QImage &dstImage ) override SIP_DEPRECATED;
QString type() const override;
int tileBufferPixels() const override;
};
#endif // QGSCUBICRASTERRESAMPLER_H

56
src/core/raster/qgsrasterresamplefilter.cpp
View File

@ -127,17 +127,18 @@ QgsRasterBlock *QgsRasterResampleFilter::block( int bandNo, QgsRectangle const
return outputBlock.release();
double oversampling = 1.0; // approximate global oversampling factor
double outputXRes;
double providerXRes = 0;
if ( mZoomedInResampler || mZoomedOutResampler )
{
QgsRasterDataProvider *provider = dynamic_cast<QgsRasterDataProvider *>( mInput->sourceInput() );
if ( provider && ( provider->capabilities() & QgsRasterDataProvider::Size ) )
{
double xRes = extent.width() / width;
double providerXRes = provider->extent().width() / provider->xSize();
double pixelRatio = xRes / providerXRes;
outputXRes = extent.width() / width;
providerXRes = provider->extent().width() / provider->xSize();
double pixelRatio = outputXRes / providerXRes;
oversampling = ( pixelRatio > mMaxOversampling ) ? mMaxOversampling : pixelRatio;
QgsDebugMsgLevel( QStringLiteral( "xRes = %1 providerXRes = %2 pixelRatio = %3 oversampling = %4" ).arg( xRes ).arg( providerXRes ).arg( pixelRatio ).arg( oversampling ), 4 );
QgsDebugMsgLevel( QStringLiteral( "xRes = %1 providerXRes = %2 pixelRatio = %3 oversampling = %4" ).arg( outputXRes ).arg( providerXRes ).arg( pixelRatio ).arg( oversampling ), 4 );
}
else
{
@ -165,12 +166,31 @@ QgsRasterBlock *QgsRasterResampleFilter::block( int bandNo, QgsRectangle const
double oversamplingX = ( static_cast< double >( width ) * oversampling ) / width;
double oversamplingY = ( static_cast< double >( height ) * oversampling ) / height;
// TODO: we must also increase the extent to get correct result on borders of parts
// we must also increase the extent to get correct result on borders of parts
int tileBufferPixels = 0;
if ( providerXRes != 0 )
{
if ( mZoomedInResampler && ( oversamplingX < 1.0 || qgsDoubleNear( oversampling, 1.0 ) ) )
{
tileBufferPixels = mZoomedInResampler->tileBufferPixels();
}
else if ( mZoomedOutResampler && oversamplingX > 1.0 )
{
tileBufferPixels = mZoomedOutResampler->tileBufferPixels();
}
}
const double sourceTileBufferSize = providerXRes * tileBufferPixels;
int resWidth = width * oversamplingX;
int resHeight = height * oversamplingY;
QgsRectangle bufferedExtent( extent.xMinimum() - sourceTileBufferSize,
extent.yMinimum() - sourceTileBufferSize,
extent.xMaximum() + sourceTileBufferSize,
extent.yMaximum() + sourceTileBufferSize
);
std::unique_ptr< QgsRasterBlock > inputBlock( mInput->block( bandNumber, extent, resWidth, resHeight, feedback ) );
int resWidth = static_cast< int >( std::round( width * oversamplingX ) ) + 2 * tileBufferPixels;
int resHeight = static_cast< int >( std::round( height * oversamplingY ) ) + 2 * tileBufferPixels;
std::unique_ptr< QgsRasterBlock > inputBlock( mInput->block( bandNumber, bufferedExtent, resWidth, resHeight, feedback ) );
if ( !inputBlock || inputBlock->isEmpty() )
{
QgsDebugMsg( QStringLiteral( "No raster data!" ) );
@ -184,21 +204,24 @@ QgsRasterBlock *QgsRasterResampleFilter::block( int bandNo, QgsRectangle const
//resample image
QImage img = inputBlock->image();
QImage dstImg;
int resampleWidth = static_cast< int >( std::round( width * ( bufferedExtent.width() / extent.width() ) ) );
int resampleHeight = static_cast< int >( std::round( height * ( bufferedExtent.height() / extent.height() ) ) );
QImage dstImg;
if ( mZoomedInResampler && ( oversamplingX < 1.0 || qgsDoubleNear( oversampling, 1.0 ) ) )
{
QgsDebugMsgLevel( QStringLiteral( "zoomed in resampling" ), 4 );
if ( QgsRasterResamplerV2 *resamplerV2 = dynamic_cast< QgsRasterResamplerV2 * >( mZoomedInResampler.get( ) ) )
{
dstImg = resamplerV2->resampleV2( img, QSize( width, height ) );
dstImg = resamplerV2->resampleV2( img, QSize( resampleWidth, resampleHeight ) );
}
else
{
// old inefficient interface
Q_NOWARN_DEPRECATED_PUSH
QImage dstImg = QImage( width, height, QImage::Format_ARGB32_Premultiplied );
QImage dstImg = QImage( resampleWidth, resampleHeight, QImage::Format_ARGB32_Premultiplied );
mZoomedInResampler->resample( img, dstImg );
Q_NOWARN_DEPRECATED_POP
}
@ -209,13 +232,13 @@ QgsRasterBlock *QgsRasterResampleFilter::block( int bandNo, QgsRectangle const
if ( QgsRasterResamplerV2 *resamplerV2 = dynamic_cast< QgsRasterResamplerV2 * >( mZoomedOutResampler.get( ) ) )
{
dstImg = resamplerV2->resampleV2( img, QSize( width, height ) );
dstImg = resamplerV2->resampleV2( img, QSize( resampleWidth, resampleHeight ) );
}
else
{
// old inefficient interface
Q_NOWARN_DEPRECATED_PUSH
QImage dstImg = QImage( width, height, QImage::Format_ARGB32_Premultiplied );
QImage dstImg = QImage( resampleWidth, resampleHeight, QImage::Format_ARGB32_Premultiplied );
mZoomedOutResampler->resample( img, dstImg );
Q_NOWARN_DEPRECATED_POP
}
@ -227,7 +250,10 @@ QgsRasterBlock *QgsRasterResampleFilter::block( int bandNo, QgsRectangle const
dstImg = img.scaled( width, height );
}
outputBlock->setImage( &dstImg );
// extract desired part of dstImage
QImage cropped = tileBufferPixels > 0 ? dstImg.copy( ( resampleWidth - width ) / 2, ( resampleHeight - height ) / 2, width, height )
: dstImg; // otherwise implicity copy, nice and cheap
outputBlock->setImage( &cropped );
return outputBlock.release(); // No resampling
}

9
src/core/raster/qgsrasterresampler.h
View File

@ -74,6 +74,15 @@ class CORE_EXPORT QgsRasterResampler
* Ownership is transferred to the caller.
*/
virtual QgsRasterResampler *clone() const = 0 SIP_FACTORY;
/**
* Returns the optional tile buffer size in pixels. This represents
* the size to buffer individual resampled tile requests prior to resampling,
* in order to avoid rendering artifacts at the edges of raster tile boundaries.
*
* \since QGIS 3.10.1
*/
virtual int tileBufferPixels() const { return 0; }
};

1
tests/src/python/CMakeLists.txt
View File

@ -186,6 +186,7 @@ ADD_PYTHON_TEST(PyQgsRasterFileWriterTask test_qgsrasterfilewritertask.py)
ADD_PYTHON_TEST(PyQgsRasterLayer test_qgsrasterlayer.py)
ADD_PYTHON_TEST(PyQgsRasterColorRampShader test_qgsrastercolorrampshader.py)
ADD_PYTHON_TEST(PyQgsRasterRange test_qgsrasterrange.py)
ADD_PYTHON_TEST(PyQgsRasterResampler test_qgsrasterresampler.py)
ADD_PYTHON_TEST(PyQgsRatioLockButton test_qgsratiolockbutton.py)
ADD_PYTHON_TEST(PyQgsRectangle test_qgsrectangle.py)
ADD_PYTHON_TEST(PyQgsReferencedGeometry test_qgsreferencedgeometry.py)

164
tests/src/python/test_qgsrasterresampler.py Normal file
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@ -0,0 +1,164 @@
# -*- coding: utf-8 -*-
"""QGIS Unit tests for QgsRasterResampler.
.. note:: This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
"""
from builtins import str
__author__ = 'Nyall Dawson'
__date__ = '14/11/2019'
__copyright__ = 'Copyright 2019, The QGIS Project'
import qgis # NOQA
import os
from qgis.PyQt.QtGui import qRed
from qgis.core import (QgsRasterLayer,
QgsRectangle,
QgsRasterResampleFilter,
QgsSingleBandGrayRenderer,
QgsCubicRasterResampler,
QgsBilinearRasterResampler
)
from utilities import unitTestDataPath
from qgis.testing import start_app, unittest
# Convenience instances in case you may need them
# not used in this test
start_app()
class TestQgsRasterResampler(unittest.TestCase):
def checkBlockContents(self, block, expected):
res = []
for r in range(block.height()):
res.append([qRed(block.color(r, c)) for c in range(block.width())])
self.assertEqual(res, expected)
def testBilinearResample(self):
path = os.path.join(unitTestDataPath(), 'landsat.tif')
raster_layer = QgsRasterLayer(path, 'test')
self.assertTrue(raster_layer.isValid())
extent = QgsRectangle(785994.37761193525511771,
3346249.2209800467826426,
786108.49096253968309611,
3346362.94137834152206779)
renderer = QgsSingleBandGrayRenderer(raster_layer.dataProvider(), 1)
filter = QgsRasterResampleFilter(renderer)
# default (nearest neighbour) resampling
block = filter.block(1, extent, 2, 2)
self.checkBlockContents(block, [[124, 127], [125, 126]])
block = filter.block(1, extent, 4, 4)
self.checkBlockContents(block, [[124, 124, 127, 127],
[124, 124, 127, 127],
[125, 125, 126, 126],
[125, 125, 126, 126]]
)
block = filter.block(1, extent, 8, 8)
self.checkBlockContents(block, [[124, 124, 124, 124, 127, 127, 127, 127],
[124, 124, 124, 124, 127, 127, 127, 127],
[124, 124, 124, 124, 127, 127, 127, 127],
[124, 124, 124, 124, 127, 127, 127, 127],
[125, 125, 125, 125, 126, 126, 126, 126],
[125, 125, 125, 125, 126, 126, 126, 126],
[125, 125, 125, 125, 126, 126, 126, 126],
[125, 125, 125, 125, 126, 126, 126, 126]])
# with resampling
filter.setZoomedInResampler(QgsBilinearRasterResampler())
block = filter.block(1, extent, 2, 2)
self.checkBlockContents(block, [[124, 127], [125, 126]])
block = filter.block(1, extent, 4, 4)
self.checkBlockContents(block,
[[124, 124, 126, 126],
[124, 124, 125, 126],
[124, 124, 125, 126],
[125, 125, 125, 126]]
)
block = filter.block(1, extent, 8, 8)
self.checkBlockContents(block,
[[124, 124, 124, 125, 125, 126, 126, 126],
[124, 124, 124, 125, 125, 126, 126, 126],
[124, 124, 124, 124, 125, 125, 126, 126],
[124, 124, 124, 124, 125, 125, 126, 126],
[124, 124, 124, 124, 125, 125, 126, 126],
[124, 124, 124, 124, 125, 125, 126, 126],
[125, 125, 125, 125, 125, 125, 126, 126],
[125, 125, 125, 125, 125, 125, 126, 126]]
)
def testCubicResample(self):
path = os.path.join(unitTestDataPath(), 'landsat.tif')
raster_layer = QgsRasterLayer(path, 'test')
self.assertTrue(raster_layer.isValid())
extent = QgsRectangle(785994.37761193525511771,
3346249.2209800467826426,
786108.49096253968309611,
3346362.94137834152206779)
renderer = QgsSingleBandGrayRenderer(raster_layer.dataProvider(), 1)
filter = QgsRasterResampleFilter(renderer)
# default (nearest neighbour) resampling
block = filter.block(1, extent, 2, 2)
self.checkBlockContents(block, [[124, 127], [125, 126]])
block = filter.block(1, extent, 4, 4)
self.checkBlockContents(block, [[124, 124, 127, 127],
[124, 124, 127, 127],
[125, 125, 126, 126],
[125, 125, 126, 126]]
)
block = filter.block(1, extent, 8, 8)
self.checkBlockContents(block, [[124, 124, 124, 124, 127, 127, 127, 127],
[124, 124, 124, 124, 127, 127, 127, 127],
[124, 124, 124, 124, 127, 127, 127, 127],
[124, 124, 124, 124, 127, 127, 127, 127],
[125, 125, 125, 125, 126, 126, 126, 126],
[125, 125, 125, 125, 126, 126, 126, 126],
[125, 125, 125, 125, 126, 126, 126, 126],
[125, 125, 125, 125, 126, 126, 126, 126]])
# with resampling
filter.setZoomedInResampler(QgsCubicRasterResampler())
block = filter.block(1, extent, 2, 2)
self.checkBlockContents(block, [[124, 127], [125, 126]])
block = filter.block(1, extent, 4, 4)
self.checkBlockContents(block,
[[124, 125, 127, 127],
[124, 125, 126, 127],
[125, 125, 126, 126],
[125, 125, 126, 126]]
)
block = filter.block(1, extent, 8, 8)
self.checkBlockContents(block,
[[124, 124, 124, 125, 126, 127, 127, 127],
[124, 124, 124, 125, 126, 127, 127, 127],
[124, 124, 124, 125, 126, 127, 127, 127],
[125, 124, 124, 125, 126, 126, 127, 126],
[125, 125, 125, 125, 126, 126, 126, 126],
[125, 125, 125, 125, 126, 126, 126, 126],
[125, 125, 125, 125, 126, 126, 126, 126],
[125, 125, 125, 125, 126, 126, 126, 126]]
)
if __name__ == '__main__':
unittest.main()