| 1 | .\"------------------------------------------------------------
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| 2 | .\" Id - set Rv,revision, and Dt, Date using rcs-Id tag.
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| 3 | .de Id
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| 4 | .ds Rv \\$3
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| 5 | .ds Dt \\$4
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| 6 | ..
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| 7 | .Id $Id: mgfelics.1 16583 2008-07-29 10:20:36Z davidb $
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| 8 | .\"------------------------------------------------------------
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| 9 | .TH mgfelics 1 \*(Dt CITRI
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| 10 | .SH NAME
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| 11 | mgfelics \- fast and efficient lossless image (de)compression
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| 12 | .SH SYNOPSIS
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| 13 | .B mgfelics
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| 14 | .B \-e
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| 15 | [
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| 16 | .BI \-k " n"
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| 17 | ]
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| 18 | .I infile
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| 19 | [
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| 20 | .I \>compressed-outfile
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| 21 | ]
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| 22 | .br
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| 23 | or
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| 24 | .br
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| 25 | .B mgfelics
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| 26 | .B \-d
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| 27 | .I compressed-infile
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| 28 | [
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| 29 | .I \>outfile
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| 30 | ]
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| 31 | .SH DESCRIPTION
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| 32 | .B mgfelics
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| 33 | is a lossless compression process which can (de)compress portable
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| 34 | bitmap files in
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| 35 | .I pgm
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| 36 | format.
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| 37 | .B mgfelics
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| 38 | writes to
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| 39 | .IR stdout .
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| 40 | .SH OPTIONS
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| 41 | .TP "\w'\fB\-k\fP \fIn\fP'u+2n"
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| 42 | .BI \-k " n"
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| 43 | An integer parameter (< 32) which controls the compression speed and
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| 44 | ratio. The value of
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| 45 | .I n
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| 46 | is included in the output stream, and therefore is not needed in the
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| 47 | decompression stage. The default value of
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| 48 | .I n
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| 49 | is equal to the number of bits required to represent each grey level.
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| 50 | .TP
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| 51 | .B \-e
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| 52 | Encodes the file
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| 53 | .IR infile ,
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| 54 | sending the output to
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| 55 | .IR stdout .
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| 56 | .TP
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| 57 | .B \-d
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| 58 | Decodes the file from
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| 59 | .IR compressed-infile ,
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| 60 | sending the output to
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| 61 | .IR stdout .
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| 62 | .SH NOTE
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| 63 | .B mgfelics
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| 64 | uses a combination of adjusted binary and Rice codes, the choice of
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| 65 | which for any given pixel depends on the environment as determined by
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| 66 | the intensity values of neighbouring pixels. The result is a very
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| 67 | fast and lossless algorithm for compressing grayscale images. The
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| 68 | optional parameter
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| 69 | .BI \-k " n"
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| 70 | corresponds to the maximum exponent of the same name in Rice encoding.
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| 71 | Smaller values of
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| 72 | .BI \-k " n"
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| 73 | can result in significant improvement in compression times with a
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| 74 | corresponding loss in compression ratio. However the reduction in
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| 75 | compression ratio with a small
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| 76 | .BI \-k " n"
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| 77 | parameter may be insignificant for many images.
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| 78 | .SH REFERENCES
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| 79 | Algorithm by Paul G. Howard and Jeffrey Scott Vitter
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| 80 | of Brown University, RI, and Duke University, NC, respectively.
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| 81 | .SH "SEE ALSO"
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| 82 | .na
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| 83 | .BR mg (1),
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| 84 | .BR mg_compression_dict (1),
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| 85 | .BR mg_fast_comp_dict (1),
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| 86 | .BR mg_get (1),
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| 87 | .BR mg_invf_dict (1),
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| 88 | .BR mg_invf_dump (1),
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| 89 | .BR mg_invf_rebuild (1),
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| 90 | .BR mg_passes (1),
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| 91 | .BR mg_perf_hash_build (1),
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| 92 | .BR mg_text_estimate (1),
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| 93 | .BR mg_weights_build (1),
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| 94 | .BR mgbilevel (1),
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| 95 | .BR mgbuild (1),
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| 96 | .BR mgdictlist (1),
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| 97 | .BR mgquery (1),
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| 98 | .BR mgstat (1),
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| 99 | .BR mgtic (1),
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| 100 | .BR mgticbuild (1),
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| 101 | .BR mgticdump (1),
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| 102 | .BR mgticprune (1),
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| 103 | .BR mgticstat (1).
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