1r.mfilter(1) Grass User's Manual r.mfilter(1)
2
6 r.mfilter - Raster file matrix filter.
7
9 raster
10
12 r.mfilter
13 r.mfilter help
14 r.mfilter [-qz] input=string output=string filter=string [repeat=inte‐
15 ger] [title="phrase"] [--overwrite]
16 Flags:
18 -q Quiet
19 -z Apply filter only to zero data values
21 --overwrite
23 Parameters:
25 input=string
26 Name of the input raster file
27 output=string
29 Name of the output raster file
30 filter=string
32 Name of the filter file
33 repeat=integer
35 Number of times to repeat the filter Default: 1
36 title=
38 Output raster file title
39
41 r.mfilter filters the raster input to produce the raster output accord‐
42 ing to the matrix filter designed by the user (see FILTERS below). The
43 filter is applied repeat times (default value is 1). The output raster
44 map layer can be given a TITLE if desired. (This TITLE should be put
45 in quotes if it contains more than one word.) With -z flag the filter
46 is applied only to zero category values in the input raster map layer.
47 The non-zero category values are not changed. Note that if there is
48 more than one filter step, this rule is applied to the intermediate
49 raster map layer -- only zero category values which result from the
50 first filter will be changed. In most cases this will NOT be the
51 desired result. Hence -z should be used only with single step filters.
52 The filter parameter defines the name of an existing, user-created UNIX
54 ASCII file whose contents is a matrix defining the way in which the
55 input file will be filtered. The format of this file is described
56 below, under FILTERS.
57 The repeat parameter defines the number of times the filter is to be
59 applied to the input data.
60
62 The filter file is a normal UNIX ASCII file designed by the user. It
63 has the following format:
64 TITLE TITLE
65 MATRIX n
66 .
67 n lines of n integers
68 .
69 DIVISOR d
70 TYPE S/P
71 TITLE A one-line TITLE for the filter. If a TITLE was not specified
74 on the command line, it can be specified here. This TITLE would
75 be used to construct a TITLE for the resulting raster map layer.
76 It should be a one-line description of the filter.
77 MATRIX The matrix (n x n) follows on the next n lines. n must be an
79 odd integer greater than or equal to 3. The matrix itself con‐
80 sists of n rows of n integers. The integers must be separated
81 from each other by at least 1 blank.
82 DIVISOR
84 The filter divisor is d. If not specified, the default is 1.
85 If the divisor is zero (0), then the divisor is dependent on the
86 category values in the neighborhood (see HOW THE FILTER WORKS
87 below).
88 TYPE The filter type. S means sequential, while P mean parallel. If
90 not specified, the default is S.
91 Sequential filtering happens in place. As the filter is applied to the
93 raster map layer, the category values that were changed in neighboring
94 cells affect the resulting category value of the current cell being
95 filtered.
96 Parallel filtering happens in such a way that the original raster map
98 layer category values are used to produce the new category value.
99 More than one filter may be specified in the filter file. The addi‐
101 tional filter(s) are described just like the first. For example, the
102 following describes two filters:
103
105 TITLE 3x3 average, non-zero data only, followed by 5x5 aver‐
107 age
108 MATRIX 3
109 1 1 1
110 1 1 1
111 1 1 1
112 DIVISOR 0
113 TYPE P
114 MATRIX 5
115 1 1 1 1 1
116 1 1 1 1 1
117 1 1 1 1 1
118 1 1 1 1 1
119 1 1 1 1 1
120 DIVISOR 25
121 TYPE P
122
125 The filter process produces a new category value for each cell in the
126 input raster map layer by multiplying the category values of the cells
127 in the n x n neighborhood around the center cell by the corresponding
128 matrix value and adding them together. If a divisor is specified, the
129 sum is divided by this divisor, rounding to the nearest integer. (If a
130 zero divisor was specified, then the divisor is computed for each cell
131 as the sum of the MATRIX values where the corresponding input cell is
132 non-zero.)
133 If more than one filter step is specified, either because the repeat
135 value was greater than one or because the filter file contained more
136 than one matrix, these steps are performed sequentially. This means
137 that first one filter is applied to the entire input raster map layer
138 to produce an intermediate result; then the next filter is applied to
139 the intermediate result to produce another intermediate result; and so
140 on, until the final filter is applied. Then the output cell is writ‐
141 ten.
142
144 If the resolution of the geographic region does not agree with the res‐
145 olution of the raster map layer, unintended resampling of the original
146 data may occur. The user should be sure that the geographic region is
147 set properly.
148
150 g.region, r.clump, r.neighbors
151
153 Michael Shapiro, U.S.Army Construction Engineering Research Laboratory
154 Last changed: $Date: 2003/05/06 14:04:17 $
156 Full index
158GRASS 6.2.2 r.mfilter(1)