root/trunk/indexers/mg/src/images/mgfelics.1 @ 3745

Revision 3745, 2.3 KB (checked in by mdewsnip, 17 years ago)

Addition of MG package for search and retrieval

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9.TH mgfelics 1 \*(Dt CITRI
10.SH NAME
11mgfelics \- fast and efficient lossless image (de)compression
12.SH SYNOPSIS
13.B mgfelics
14.B \-e
15[
16.BI \-k " n"
17]
18.I infile
19[
20.I \>compressed-outfile
21]
22.br
23or
24.br
25.B mgfelics
26.B \-d
27.I compressed-infile
28[
29.I \>outfile
30]
31.SH DESCRIPTION
32.B mgfelics
33is a lossless compression process which can (de)compress portable
34bitmap files in
35.I pgm
36format.
37.B mgfelics
38writes to
39.IR stdout .
40.SH OPTIONS
41.TP "\w'\fB\-k\fP \fIn\fP'u+2n"
42.BI \-k " n"
43An integer parameter (< 32) which controls the compression speed and
44ratio.  The value of
45.I n
46is included in the output stream, and therefore is not needed in the
47decompression stage.  The default value of
48.I n
49is equal to the number of bits required to represent each grey level.
50.TP
51.B \-e
52Encodes the file
53.IR infile ,
54sending the output to
55.IR stdout .
56.TP
57.B \-d
58Decodes the file from
59.IR compressed-infile ,
60sending the output to
61.IR stdout .
62.SH NOTE
63.B mgfelics
64uses a combination of adjusted binary and Rice codes, the choice of
65which for any given pixel depends on the environment as determined by
66the intensity values of neighbouring pixels.  The result is a very
67fast and lossless algorithm for compressing grayscale images.  The
68optional parameter
69.BI \-k " n"
70corresponds to the maximum exponent of the same name in Rice encoding.
71Smaller values of
72.BI \-k " n"
73can result in significant improvement in compression times with a
74corresponding loss in compression ratio.  However the reduction in
75compression ratio with a small
76.BI \-k " n"
77parameter may be insignificant for many images.
78.SH REFERENCES
79Algorithm by Paul G. Howard and Jeffrey Scott Vitter
80of Brown University, RI, and Duke University, NC, respectively.
81.SH "SEE ALSO"
82.na
83.BR mg (1),
84.BR mg_compression_dict (1),
85.BR mg_fast_comp_dict (1),
86.BR mg_get (1),
87.BR mg_invf_dict (1),
88.BR mg_invf_dump (1),
89.BR mg_invf_rebuild (1),
90.BR mg_passes (1),
91.BR mg_perf_hash_build (1),
92.BR mg_text_estimate (1),
93.BR mg_weights_build (1),
94.BR mgbilevel (1),
95.BR mgbuild (1),
96.BR mgdictlist (1),
97.BR mgquery (1),
98.BR mgstat (1),
99.BR mgtic (1),
100.BR mgticbuild (1),
101.BR mgticdump (1),
102.BR mgticprune (1),
103.BR mgticstat (1).
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