QGIS API Documentation  2.99.0-Master (b8fd1fd)
qgsderivativefilter.cpp
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1 /***************************************************************************
2  qgsderivativefilter.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 "qgsderivativefilter.h"
19 
20 QgsDerivativeFilter::QgsDerivativeFilter( const QString &inputFile, const QString &outputFile, const QString &outputFormat )
21  : QgsNineCellFilter( inputFile, outputFile, outputFormat )
22 {
23 
24 }
25 
26 float QgsDerivativeFilter::calcFirstDerX( float *x11, float *x21, float *x31, float *x12, float *x22, float *x32, float *x13, float *x23, float *x33 )
27 {
28  //the basic formula would be simple, but we need to test for nodata values...
29  //return (( (*x31 - *x11) + 2 * (*x32 - *x12) + (*x33 - *x13) ) / (8 * mCellSizeX));
30 
31  int weight = 0;
32  double sum = 0;
33 
34  //first row
35  if ( *x31 != mInputNodataValue && *x11 != mInputNodataValue ) //the normal case
36  {
37  sum += ( *x31 - *x11 );
38  weight += 2;
39  }
40  else if ( *x31 == mInputNodataValue && *x11 != mInputNodataValue && *x21 != mInputNodataValue ) //probably 3x3 window is at the border
41  {
42  sum += ( *x21 - *x11 );
43  weight += 1;
44  }
45  else if ( *x11 == mInputNodataValue && *x31 != mInputNodataValue && *x21 != mInputNodataValue ) //probably 3x3 window is at the border
46  {
47  sum += ( *x31 - *x21 );
48  weight += 1;
49  }
50 
51  //second row
52  if ( *x32 != mInputNodataValue && *x12 != mInputNodataValue ) //the normal case
53  {
54  sum += 2 * ( *x32 - *x12 );
55  weight += 4;
56  }
57  else if ( *x32 == mInputNodataValue && *x12 != mInputNodataValue && *x22 != mInputNodataValue )
58  {
59  sum += 2 * ( *x22 - *x12 );
60  weight += 2;
61  }
62  else if ( *x12 == mInputNodataValue && *x32 != mInputNodataValue && *x22 != mInputNodataValue )
63  {
64  sum += 2 * ( *x32 - *x22 );
65  weight += 2;
66  }
67 
68  //third row
69  if ( *x33 != mInputNodataValue && *x13 != mInputNodataValue ) //the normal case
70  {
71  sum += ( *x33 - *x13 );
72  weight += 2;
73  }
74  else if ( *x33 == mInputNodataValue && *x13 != mInputNodataValue && *x23 != mInputNodataValue )
75  {
76  sum += ( *x23 - *x13 );
77  weight += 1;
78  }
79  else if ( *x13 == mInputNodataValue && *x33 != mInputNodataValue && *x23 != mInputNodataValue )
80  {
81  sum += ( *x33 - *x23 );
82  weight += 1;
83  }
84 
85  if ( weight == 0 )
86  {
87  return mOutputNodataValue;
88  }
89 
90  return sum / ( weight * mCellSizeX * mZFactor );
91 }
92 
93 float QgsDerivativeFilter::calcFirstDerY( float *x11, float *x21, float *x31, float *x12, float *x22, float *x32, float *x13, float *x23, float *x33 )
94 {
95  //the basic formula would be simple, but we need to test for nodata values...
96  //return (((*x11 - *x13) + 2 * (*x21 - *x23) + (*x31 - *x33)) / ( 8 * mCellSizeY));
97 
98  double sum = 0;
99  int weight = 0;
100 
101  //first row
102  if ( *x11 != mInputNodataValue && *x13 != mInputNodataValue ) //normal case
103  {
104  sum += ( *x11 - *x13 );
105  weight += 2;
106  }
107  else if ( *x11 == mInputNodataValue && *x13 != mInputNodataValue && *x12 != mInputNodataValue )
108  {
109  sum += ( *x12 - *x13 );
110  weight += 1;
111  }
112  else if ( *x31 == mInputNodataValue && *x11 != mInputNodataValue && *x12 != mInputNodataValue )
113  {
114  sum += ( *x11 - *x12 );
115  weight += 1;
116  }
117 
118  //second row
119  if ( *x21 != mInputNodataValue && *x23 != mInputNodataValue )
120  {
121  sum += 2 * ( *x21 - *x23 );
122  weight += 4;
123  }
124  else if ( *x21 == mInputNodataValue && *x23 != mInputNodataValue && *x22 != mInputNodataValue )
125  {
126  sum += 2 * ( *x22 - *x23 );
127  weight += 2;
128  }
129  else if ( *x23 == mInputNodataValue && *x21 != mInputNodataValue && *x22 != mInputNodataValue )
130  {
131  sum += 2 * ( *x21 - *x22 );
132  weight += 2;
133  }
134 
135  //third row
136  if ( *x31 != mInputNodataValue && *x33 != mInputNodataValue )
137  {
138  sum += ( *x31 - *x33 );
139  weight += 2;
140  }
141  else if ( *x31 == mInputNodataValue && *x33 != mInputNodataValue && *x32 != mInputNodataValue )
142  {
143  sum += ( *x32 - *x33 );
144  weight += 1;
145  }
146  else if ( *x33 == mInputNodataValue && *x31 != mInputNodataValue && *x32 != mInputNodataValue )
147  {
148  sum += ( *x31 - *x32 );
149  weight += 1;
150  }
151 
152  if ( weight == 0 )
153  {
154  return mOutputNodataValue;
155  }
156 
157  return sum / ( weight * mCellSizeY * mZFactor );
158 }
159 
160 
161 
162 
163 
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)
QgsDerivativeFilter(const QString &inputFile, const QString &outputFile, const QString &outputFormat)
float mOutputNodataValue
The nodata value of the output layer.
double mZFactor
Scale factor for z-value if x-/y- units are different to z-units (111120 for degree->meters and 37040...
float mInputNodataValue
The nodata value of the input layer.
Base class for raster analysis methods that work with a 3x3 cell filter and calculate the value of ea...