Quantum GIS API Documentation  1.8
src/analysis/raster/qgstotalcurvaturefilter.cpp
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00001 /***************************************************************************
00002                           qgstotalcurvaturefilter.h  -  description
00003                              -------------------
00004     begin                : August 21th, 2009
00005     copyright            : (C) 2009 by Marco Hugentobler
00006     email                : marco dot hugentobler at karto dot baug dot ethz dot ch
00007  ***************************************************************************/
00008 
00009 /***************************************************************************
00010  *                                                                         *
00011  *   This program is free software; you can redistribute it and/or modify  *
00012  *   it under the terms of the GNU General Public License as published by  *
00013  *   the Free Software Foundation; either version 2 of the License, or     *
00014  *   (at your option) any later version.                                   *
00015  *                                                                         *
00016  ***************************************************************************/
00017 
00018 #include "qgstotalcurvaturefilter.h"
00019 
00020 QgsTotalCurvatureFilter::QgsTotalCurvatureFilter( const QString& inputFile, const QString& outputFile, const QString& outputFormat )
00021     : QgsNineCellFilter( inputFile, outputFile, outputFormat )
00022 {
00023 
00024 }
00025 
00026 QgsTotalCurvatureFilter::~QgsTotalCurvatureFilter()
00027 {
00028 
00029 }
00030 
00031 float QgsTotalCurvatureFilter::processNineCellWindow( float* x11, float* x21, float* x31, float* x12,
00032     float* x22, float* x32, float* x13, float* x23, float* x33 )
00033 {
00034   //return nodata if one value is the nodata value
00035   if ( *x11 == mInputNodataValue || *x21 == mInputNodataValue || *x31 == mInputNodataValue || *x12 == mInputNodataValue
00036        || *x22 == mInputNodataValue || *x32 == mInputNodataValue || *x13 == mInputNodataValue || *x23 == mInputNodataValue
00037        || *x33 == mInputNodataValue )
00038   {
00039     return mOutputNodataValue;
00040   }
00041 
00042   double cellSizeAvg = ( mCellSizeX + mCellSizeY ) / 2.0;
00043   double dxx = ( *x32 - 2 * *x22 + *x12 ) / ( mCellSizeX * mCellSizeX );
00044   double dyy = ( -*x11 + *x31 + *x13 - *x33 ) / ( 4 * cellSizeAvg * cellSizeAvg );
00045   double dxy = ( *x21 - 2 * *x22 + *x23 ) / ( mCellSizeY * mCellSizeY );
00046 
00047   return dxx*dxx + 2*dxy*dxy + dyy*dyy;
00048 }
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