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.1 439 1999-08-10 21:23:37Z sjboddie $
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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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