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qgsterraindownloader.cpp
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qgsterraindownloader.cpp
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/***************************************************************************
qgsterraindownloader.cpp
--------------------------------------
Date : March 2019
Copyright : (C) 2019 by Martin Dobias
Email : wonder dot sk at gmail dot com
***************************************************************************
* *
* 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. *
* *
***************************************************************************/
#include "qgsterraindownloader.h"
#include "qgslogger.h"
#include "qgsrasterlayer.h"
#include "qgsgdalutils.h"
QgsTerrainDownloader::QgsTerrainDownloader()
{
setDataSource( defaultDataSource() );
// the whole world is projected to a square:
// X going from 180 W to 180 E
// Y going from ~85 N to ~85 S (=atan(sinh(pi)) ... to get a square)
Q_NOWARN_DEPRECATED_PUSH
QgsCoordinateTransform ct( QgsCoordinateReferenceSystem( QStringLiteral( "EPSG:4326" ) ), QgsCoordinateReferenceSystem( "EPSG:3857" ) );
Q_NOWARN_DEPRECATED_POP
QgsPointXY topLeftLonLat( -180, 180.0 / M_PI * std::atan( std::sinh( M_PI ) ) );
QgsPointXY bottomRightLonLat( 180, 180.0 / M_PI * std::atan( std::sinh( -M_PI ) ) );
QgsPointXY topLeft = ct.transform( topLeftLonLat );
QgsPointXY bottomRight = ct.transform( bottomRightLonLat );
mXSpan = ( bottomRight.x() - topLeft.x() );
}
QgsTerrainDownloader::~QgsTerrainDownloader() = default;
QgsTerrainDownloader::DataSource QgsTerrainDownloader::defaultDataSource()
{
// using terrain tiles stored on AWS and listed within Registry of Open Data on AWS
// see https://registry.opendata.aws/terrain-tiles/
//
// tiles are generated using a variety of sources (SRTM, ETOPO1 and more detailed data for some countries)
// for more details and attribution see https://github.com/tilezen/joerd/blob/master/docs/data-sources.md
DataSource ds;
ds.uri = "https://s3.amazonaws.com/elevation-tiles-prod/terrarium/{z}/{x}/{y}.png";
ds.zMin = 0;
ds.zMax = 15;
return ds;
}
void QgsTerrainDownloader::setDataSource( const QgsTerrainDownloader::DataSource &ds )
{
mDataSource = ds;
QString uri = QString( "type=xyz&url=%1&zmin=%2&zmax=%3" ).arg( mDataSource.uri ).arg( mDataSource.zMin ).arg( mDataSource.zMax );
mOnlineDtm.reset( new QgsRasterLayer( uri, "terrarium", "wms" ) );
}
void QgsTerrainDownloader::adjustExtentAndResolution( double mupp, const QgsRectangle &extentOrig, QgsRectangle &extent, int &res )
{
double xMin = floor( extentOrig.xMinimum() / mupp ) * mupp;
double xMax = ceil( extentOrig.xMaximum() / mupp ) * mupp;
double yMin = floor( extentOrig.yMinimum() / mupp ) * mupp;
double yMax = ceil( extentOrig.yMaximum() / mupp ) * mupp;
extent = QgsRectangle( xMin, yMin, xMax, yMax );
res = round( ( xMax - xMin ) / mupp );
}
double QgsTerrainDownloader::findBestTileResolution( double requestedMupp )
{
int zoom = 0;
for ( ; zoom <= 15; ++zoom )
{
double tileMupp = mXSpan / ( 256 * ( 1 << zoom ) );
if ( tileMupp <= requestedMupp )
break;
}
if ( zoom > 15 ) zoom = 15;
double finalMupp = mXSpan / ( 256 * ( 1 << zoom ) );
return finalMupp;
}
void QgsTerrainDownloader::tileImageToHeightMap( const QImage &img, QByteArray &heightMap )
{
// for description of the "terrarium" format:
// https://github.com/tilezen/joerd/blob/master/docs/formats.md
// assuming ARGB premultiplied but with alpha 255
const QRgb *rgb = reinterpret_cast<const QRgb *>( img.constBits() );
int count = img.width() * img.height();
heightMap.resize( sizeof( float ) * count );
float *hData = reinterpret_cast<float *>( heightMap.data() );
for ( int i = 0; i < count; ++i )
{
QRgb c = rgb[i];
if ( qAlpha( c ) == 255 )
{
float h = qRed( c ) * 256 + qGreen( c ) + qBlue( c ) / 256.f - 32768;
*hData++ = h;
}
else
{
*hData++ = std::numeric_limits<float>::quiet_NaN();
}
}
}
QByteArray QgsTerrainDownloader::getHeightMap( const QgsRectangle &extentOrig, int res, const QgsCoordinateReferenceSystem &destCrs, const QgsCoordinateTransformContext &context, QString tmpFilenameImg, QString tmpFilenameTif )
{
if ( !mOnlineDtm || !mOnlineDtm->isValid() )
{
QgsDebugMsg( "missing a valid data source" );
return QByteArray();
}
QgsRectangle extentTr = extentOrig;
if ( destCrs != mOnlineDtm->crs() )
{
// if in different CRS - need to reproject extent and resolution
QgsCoordinateTransform ct( destCrs, mOnlineDtm->crs(), context );
extentTr = ct.transformBoundingBox( extentOrig );
}
double requestedMupp = extentTr.width() / res;
double finalMupp = findBestTileResolution( requestedMupp );
// adjust extent to match native resolution of terrain tiles
QgsRectangle extent;
int resOrig = res;
adjustExtentAndResolution( finalMupp, extentTr, extent, res );
// request tile
QgsRasterBlock *b = mOnlineDtm->dataProvider()->block( 1, extent, res, res );
QImage img = b->image();
delete b;
if ( !tmpFilenameImg.isEmpty() )
img.save( tmpFilenameImg );
// convert to height data
QByteArray heightMap;
tileImageToHeightMap( img, heightMap );
// prepare source/destination datasets for resampling
gdal::dataset_unique_ptr hSrcDS( QgsGdalUtils::createSingleBandMemoryDataset( GDT_Float32, extent, res, res, mOnlineDtm->crs() ) );
gdal::dataset_unique_ptr hDstDS;
if ( !tmpFilenameTif.isEmpty() )
hDstDS = QgsGdalUtils::createSingleBandTiffDataset( tmpFilenameTif, GDT_Float32, extentOrig, resOrig, resOrig, destCrs );
else
hDstDS = QgsGdalUtils::createSingleBandMemoryDataset( GDT_Float32, extentOrig, resOrig, resOrig, destCrs );
if ( !hSrcDS || !hDstDS )
{
QgsDebugMsg( "failed to create GDAL dataset for heightmap" );
return QByteArray();
}
CPLErr err = GDALRasterIO( GDALGetRasterBand( hSrcDS.get(), 1 ), GF_Write, 0, 0, res, res, heightMap.data(), res, res, GDT_Float32, 0, 0 );
if ( err != CE_None )
{
QgsDebugMsg( "failed to write heightmap data to GDAL dataset" );
return QByteArray();
}
// resample to the desired extent + resolution
QgsGdalUtils::resampleSingleBandRaster( hSrcDS.get(), hDstDS.get(), GRA_Bilinear );
QByteArray heightMapOut;
heightMapOut.resize( resOrig * resOrig * sizeof( float ) );
char *data = heightMapOut.data();
// read the data back
CPLErr err2 = GDALRasterIO( GDALGetRasterBand( hDstDS.get(), 1 ), GF_Read, 0, 0, resOrig, resOrig, data, resOrig, resOrig, GDT_Float32, 0, 0 );
if ( err2 != CE_None )
{
QgsDebugMsg( "failed to read heightmap data from GDAL dataset" );
return QByteArray();
}
return heightMapOut;
}