1r.mfilter(1) Grass User's Manual r.mfilter(1)
2
6 r.mfilter - Raster map matrix filter.
7
9 raster, map algebra
10
12 r.mfilter
13 r.mfilter help
14 r.mfilter [-qz] input=name output=name filter=name [repeat=integer]
15 [title=string] [--overwrite] [--verbose] [--quiet]
16 Flags:
18 -q
19 Quiet
20 -z
22 Apply filter only to zero data values
23 --overwrite
25 Allow output files to overwrite existing files
26 --verbose
28 Verbose module output
29 --quiet
31 Quiet module output
32 Parameters:
34 input=name
35 Name of input raster map
36 output=name
38 Name for output raster map
39 filter=name
41 Name of filter file
42 repeat=integer
44 Number of times to repeat the filter
45 Default: 1
46 title=string
48 Output raster map title
49
51 r.mfilter filters the raster input to produce the raster output accord‐
52 ing to the matrix filter designed by the user (see FILTERS below). The
53 filter is applied repeat times (default value is 1). The output raster
54 map layer can be given a TITLE if desired. (This TITLE should be put
55 in quotes if it contains more than one word.) With -z flag the filter
56 is applied only to zero category values in the input raster map layer.
57 The non-zero category values are not changed. Note that if there is
58 more than one filter step, this rule is applied to the intermediate
59 raster map layer -- only zero category values which result from the
60 first filter will be changed. In most cases this will NOT be the
61 desired result. Hence -z should be used only with single step filters.
62 The filter parameter defines the name of an existing, user-created UNIX
64 ASCII file whose contents is a matrix defining the way in which the
65 input file will be filtered. The format of this file is described
66 below, under FILTERS.
67 The repeat parameter defines the number of times the filter is to be
69 applied to the input data.
70
72 The filter file is a normal UNIX ASCII file designed by the user. It
73 has the following format:
74 TITLE TITLE
75 MATRIX n
76 .
77 n lines of n integers
78 .
79 DIVISOR d
80 TYPE S/P
81 TITLE
84 A one-line TITLE for the filter. If a TITLE was not specified
85 on the command line, it can be specified here. This TITLE would
86 be used to construct a TITLE for the resulting raster map layer.
87 It should be a one-line description of the filter.
88 MATRIX
90 The matrix (n x n) follows on the next n lines. n must be an
91 odd integer greater than or equal to 3. The matrix itself con‐
92 sists of n rows of n integers. The integers must be separated
93 from each other by at least 1 blank.
94 DIVISOR
96 The filter divisor is d. If not specified, the default is 1.
97 If the divisor is zero (0), then the divisor is dependent on the
98 category values in the neighborhood (see HOW THE FILTER WORKS
99 below).
100 TYPE
102 The filter type. S means sequential, while P mean parallel. If
103 not specified, the default is S.
104 Sequential filtering happens in place. As the filter is applied to the
106 raster map layer, the category values that were changed in neighboring
107 cells affect the resulting category value of the current cell being
108 filtered.
109 Parallel filtering happens in such a way that the original raster map
111 layer category values are used to produce the new category value.
112 More than one filter may be specified in the filter file. The addi‐
114 tional filter(s) are described just like the first. For example, the
115 following describes two filters:
116
118 TITLE 3x3 average, non-zero data only, followed by 5x5 aver‐
120 age
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
138 The filter process produces a new category value for each cell in the
139 input raster map layer by multiplying the category values of the cells
140 in the n x n neighborhood around the center cell by the corresponding
141 matrix value and adding them together. If a divisor is specified, the
142 sum is divided by this divisor, rounding to the nearest integer. (If a
143 zero divisor was specified, then the divisor is computed for each cell
144 as the sum of the MATRIX values where the corresponding input cell is
145 non-zero.)
146 If more than one filter step is specified, either because the repeat
148 value was greater than one or because the filter file contained more
149 than one matrix, these steps are performed sequentially. This means
150 that first one filter is applied to the entire input raster map layer
151 to produce an intermediate result; then the next filter is applied to
152 the intermediate result to produce another intermediate result; and so
153 on, until the final filter is applied. Then the output cell is writ‐
154 ten.
155
157 If the resolution of the geographic region does not agree with the res‐
158 olution of the raster map layer, unintended resampling of the original
159 data may occur. The user should be sure that the geographic region is
160 set properly.
161
163 g.region, r.clump, r.neighbors
164
166 Michael Shapiro, U.S.Army Construction Engineering Research Laboratory
167 Last changed: $Date: 2007-03-20 04:30:13 +0100 (Tue, 20 Mar 2007) $
169 Full index
171 © 2003-2008 GRASS Development Team
173GRASS 6.3.0 r.mfilter(1)