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qgsaspectfilter.cpp
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1 /***************************************************************************
2  qgsaspectfilter.cpp - description
3  -----------------------------------
4  begin : August 7th, 2009
5  copyright : (C) 2009 by Marco Hugentobler
6  email : marco dot hugentobler at karto dot baug dot ethz dot ch
7  ***************************************************************************/
8 
9 /***************************************************************************
10  * *
11  * This program is free software; you can redistribute it and/or modify *
12  * it under the terms of the GNU General Public License as published by *
13  * the Free Software Foundation; either version 2 of the License, or *
14  * (at your option) any later version. *
15  * *
16  ***************************************************************************/
17 
18 #include "qgsaspectfilter.h"
19 
20 QgsAspectFilter::QgsAspectFilter( const QString& inputFile, const QString& outputFile, const QString& outputFormat ) :
21  QgsDerivativeFilter( inputFile, outputFile, outputFormat )
22 {
23 
24 }
25 
27 {
28 
29 }
30 
32  float* x11, float* x21, float* x31,
33  float* x12, float* x22, float* x32,
34  float* x13, float* x23, float* x33 )
35 {
36  float derX = calcFirstDerX( x11, x21, x31, x12, x22, x32, x13, x23, x33 );
37  float derY = calcFirstDerY( x11, x21, x31, x12, x22, x32, x13, x23, x33 );
38 
39  if ( derX == mOutputNodataValue ||
40  derY == mOutputNodataValue ||
41  ( derX == 0.0 && derY == 0.0 ) )
42  {
43  return mOutputNodataValue;
44  }
45  else
46  {
47  return 180.0 + atan2( derX, derY ) * 180.0 / M_PI;
48  }
49 }
50 
float calcFirstDerY(float *x11, float *x21, float *x31, float *x12, float *x22, float *x32, float *x13, float *x23, float *x33)
Calculates the first order derivative in y-direction according to Horn (1981)
float calcFirstDerX(float *x11, float *x21, float *x31, float *x12, float *x22, float *x32, float *x13, float *x23, float *x33)
Calculates the first order derivative in x-direction according to Horn (1981)
QgsAspectFilter(const QString &inputFile, const QString &outputFile, const QString &outputFormat)
#define M_PI
Adds the ability to calculate derivatives in x- and y-directions.
float mOutputNodataValue
The nodata value of the output layer.
float processNineCellWindow(float *x11, float *x21, float *x31, float *x12, float *x22, float *x32, float *x13, float *x23, float *x33)
Calculates output value from nine input values.