1r.mfilter(1) Grass User's Manual r.mfilter(1)
2
6 r.mfilter - Performs raster map matrix filter.
7
9 raster, algebra, statistics, filter
10
12 r.mfilter
13 r.mfilter --help
14 r.mfilter [-z] input=name output=name filter=name [repeat=integer]
15 [title=string] [--overwrite] [--help] [--verbose] [--quiet]
16 [--ui]
17 Flags:
19 -z
20 Apply filter only to null data values
21 --overwrite
23 Allow output files to overwrite existing files
24 --help
26 Print usage summary
27 --verbose
29 Verbose module output
30 --quiet
32 Quiet module output
33 --ui
35 Force launching GUI dialog
36 Parameters:
38 input=name [required]
39 Name of input raster map
40 output=name [required]
42 Name for output raster map
43 filter=name [required]
45 Path to filter file
46 repeat=integer
48 Number of times to repeat the filter
49 Default: 1
50 title=string
52 Output raster map title
53
55 r.mfilter filters the raster input to produce the raster output accord‐
56 ing to the matrix filter designed by the user (see FILTERS below). The
57 filter is applied repeat times (default value is 1). The output raster
58 map layer can be given a TITLE if desired. (This TITLE should be put
59 in quotes if it contains more than one word.) With -z flag the filter
60 is applied only to null values in the input raster map layer. The
61 non-null category values are not changed. Note that if there is more
62 than one filter step, this rule is applied to the intermediate raster
63 map layer -- only null category values which result from the first fil‐
64 ter will be changed. In most cases this will NOT be the desired
65 result. Hence -z should be used only with single step filters.
66 The filter parameter defines the name of an existing, user-created UNIX
68 ASCII file whose contents is a matrix defining the way in which the
69 input file will be filtered. The format of this file is described
70 below, under FILTERS.
71 The repeat parameter defines the number of times the filter is to be
73 applied to the input data.
74
76 The filter file is a normal UNIX ASCII file designed by the user. It
77 has the following format:
78 TITLE TITLE
79 MATRIX n
80 .
81 n lines of n values
82 .
83 DIVISOR d
84 TYPE S/P
85 TITLE
87 A one-line TITLE for the filter. If a TITLE was not specified on
88 the command line, it can be specified here. This TITLE would be
89 used to construct a TITLE for the resulting raster map layer. It
90 should be a one-line description of the filter.
91 MATRIX
93 The matrix (n x n) follows on the next n lines. n must be an odd
94 integer greater than or equal to 3. The matrix itself consists of
95 n rows of n values. The values must be separated from each other
96 by at least 1 blank.
97 DIVISOR
99 The filter divisor is d. If not specified, the default is 1. If
100 the divisor is zero (0), then the divisor is dependent on the cate‐
101 gory values in the neighborhood (see HOW THE FILTER WORKS below).
102 TYPE
104 The filter type. S means sequential, while P mean parallel. If
105 not specified, the default is S.
106 Sequential filtering happens in place. As the filter is applied to the
108 raster map layer, the category values that were changed in neighboring
109 cells affect the resulting category value of the current cell being
110 filtered.
111 Parallel filtering happens in such a way that the original raster map
113 layer category values are used to produce the new category value.
114 More than one filter may be specified in the filter file. The addi‐
116 tional filter(s) are described just like the first. For example, the
117 following describes two filters:
118
120 TITLE 3x3 average, non-null data only, followed by 5x5 average
121 MATRIX 3
122 1 1 1
123 1 1 1
124 1 1 1
125 DIVISOR 0
126 TYPE P
127 MATRIX 5
128 1 1 1 1 1
129 1 1 1 1 1
130 1 1 1 1 1
131 1 1 1 1 1
132 1 1 1 1 1
133 DIVISOR 25
134 TYPE P
135
137 The filter process produces a new category value for each cell in the
138 input raster map layer by multiplying the category values of the cells
139 in the n x n neighborhood around the center cell by the corresponding
140 matrix value and adding them together. If a divisor is specified, the
141 sum is divided by this divisor. (If a zero divisor was specified, then
142 the divisor is computed for each cell as the sum of the MATRIX values
143 where the corresponding input cell is non-null.)
144 If more than one filter step is specified, either because the repeat
146 value was greater than one or because the filter file contained more
147 than one matrix, these steps are performed sequentially. This means
148 that first one filter is applied to the entire input raster map layer
149 to produce an intermediate result; then the next filter is applied to
150 the intermediate result to produce another intermediate result; and so
151 on, until the final filter is applied. Then the output cell is writ‐
152 ten.
153
155 If the resolution of the geographic region does not agree with the res‐
156 olution of the raster map layer, unintended resampling of the original
157 data may occur. The user should be sure that the geographic region is
158 set properly.
159
161 g.region, r.clump, r.neighbors, r.resamp.filter
162
164 Glynn Clements. Based upon r.mfilter, by Michael Shapiro, U.S.Army
165 Construction Engineering Research Laboratory
166
168 Available at: r.mfilter source code (history)
169 Main index | Raster index | Topics index | Keywords index | Graphical
171 index | Full index
172 © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual
174GRASS 7.8.2 r.mfilter(1)