QGIS API Documentation 3.37.0-Master (fdefdf9c27f)
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
20QgsDerivativeFilter::QgsDerivativeFilter( const QString &inputFile, const QString &outputFile, const QString &outputFormat )
21 : QgsNineCellFilter( inputFile, outputFile, outputFormat )
22{
23
24}
25
26float QgsDerivativeFilter::calcFirstDerX( float *x11, float *x21, float *x31, float *x12, float *x22, float *x32, float *x13, float *x23, float *x33 ) const
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
93float QgsDerivativeFilter::calcFirstDerY( float *x11, float *x21, float *x31, float *x12, float *x22, float *x32, float *x13, float *x23, float *x33 ) const
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
QgsDerivativeFilter(const QString &inputFile, const QString &outputFile, const QString &outputFormat)
float calcFirstDerX(float *x11, float *x21, float *x31, float *x12, float *x22, float *x32, float *x13, float *x23, float *x33) const
Calculates the first order derivative in x-direction according to Horn (1981)
float calcFirstDerY(float *x11, float *x21, float *x31, float *x12, float *x22, float *x32, float *x13, float *x23, float *x33) const
Calculates the first order derivative in y-direction according to Horn (1981)
Base class for raster analysis methods that work with a 3x3 cell filter and calculate the value of ea...
float mInputNodataValue
The nodata value of the input layer.
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...