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qgshillshadefilter.cpp
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qgshillshadefilter.cpp
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/***************************************************************************
qgshillshadefilter.h - description
--------------------------------
begin : September 26th, 2011
copyright : (C) 2011 by Marco Hugentobler
email : marco dot hugentobler at sourcepole dot ch
***************************************************************************/
/***************************************************************************
* *
* 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 "qgshillshadefilter.h"
QgsHillshadeFilter::QgsHillshadeFilter( const QString &inputFile, const QString &outputFile, const QString &outputFormat, double lightAzimuth,
double lightAngle )
: QgsDerivativeFilter( inputFile, outputFile, outputFormat )
, mLightAzimuth( lightAzimuth )
, mLightAngle( lightAngle )
{
}
float QgsHillshadeFilter::processNineCellWindow( float *x11, float *x21, float *x31,
float *x12, float *x22, float *x32,
float *x13, float *x23, float *x33 )
{
float derX = calcFirstDerX( x11, x21, x31, x12, x22, x32, x13, x23, x33 );
float derY = calcFirstDerY( x11, x21, x31, x12, x22, x32, x13, x23, x33 );
if ( derX == mOutputNodataValue || derY == mOutputNodataValue )
{
return mOutputNodataValue;
}
float zenith_rad = mLightAngle * M_PI / 180.0;
float slope_rad = std::atan( std::sqrt( derX * derX + derY * derY ) );
float azimuth_rad = mLightAzimuth * M_PI / 180.0;
float aspect_rad = 0;
if ( derX == 0 && derY == 0 ) //aspect undefined, take a neutral value. Better solutions?
{
aspect_rad = azimuth_rad / 2.0;
}
else
{
aspect_rad = M_PI + std::atan2( derX, derY );
}
return std::max( 0.0, 255.0 * ( ( std::cos( zenith_rad ) * std::cos( slope_rad ) ) + ( std::sin( zenith_rad ) * std::sin( slope_rad ) * std::cos( azimuth_rad - aspect_rad ) ) ) );
}