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1 .\"
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2 .\" wm_koch_d.1 - the *roff document processor man page source
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3 .\"
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4 .TH wm_koch_d 1 "98/07/05" "Watermarking, Version 1.0"
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5 .SH NAME
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6 .B wm_koch_d
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7 \- a program to extract signature bits that have been embedded into
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8 the DCT coefficients of an image
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9 .SH SYNOPSIS
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10 .B wm_koch_d
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11 [
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12 .B \-h
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13 ]
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14 [
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15 .BI \-o \ ofile
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16 ]
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17 [
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18 .BI \-q \ number
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19 ]
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20 [
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21 .BI \-v \ number
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22 ]
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23 .BI \-s \ sfile
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24 .IR file
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25 .SH DESCRIPTION
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26 .B wm_koch_d
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27 is a program to extract signature bits from the 8x8 DCT coefficients of
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28 an image, embedded with the
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29 .B wm_koch_e
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30 watermarking program.
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31 .B cmp_koch_sig
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32 program compares and tests the extracted signature against the original signature.
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33 .PP
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34 The input image is in PGM (portable graymap) format.
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35 .PP
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36 If
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37 .I file
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38 or
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39 .I ofile
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40 is not specified, then standard input or standard output is
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41 used. The signature
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42 .I sfile
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43 is a mandatory parameter however.
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44 .PP
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45 Please refer to E. Koch's paper "Towards Robust and Hidden
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46 Image Copyright", 1995, to get an idea about the algorithm.
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47 .PP
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48 .SH OPTIONS
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49 .TP
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50 .B \-h
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51 Print a help message.
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52 .TP
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53 .BI \-o \ ofile
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54 Output the extracted signature to
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55 .I ofile
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56 instead of standard output.
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57 .TP
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58 .BI \-q \ number
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59 Quality/robustness factor used to extract the signature.
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60 Overrides setting from signature file.
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61 .TP
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62 .BI \-s \ sfile
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63 The original signature file. See
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64 .B gen_koch_sig
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65 (1) for a description of the file format. Mandatory parameter.
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66 .BI \-v \ number
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67 Verbosity level. 0 for quiet operation, higher numbers for more
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68 output. Default value: 0.
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69 .TP
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70 .IR file
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71 Signed (watermarked) input image in PGM format. Default: standard input.
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72 .PP
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73 .SH OUTPUT
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74 The extracted signature is written to standard output
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75 or, optionally, to
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76 .I ofile.
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77 .PP
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78 The extraction algorithm examines the relationship between two random
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79 coefficients of randomly selected 8x8 DCT blocks to reconstruct the
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80 signature bits.
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81 .PP
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82 The output file has the following format:
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83 .TP
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84 .B KCSG
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85 Magic to identify file type.
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86 .TP
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87 .I number
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88 The length of the signature in bits.
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89 .TP
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90 .I number
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91 The quality/robustness factor.
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92 .TP
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93 .I number
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94 The seed value for the pseudo-random number generator.
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95 .TP
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96 .I string
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97 The actual signature bytes.
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98 .PP
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99 .SH AUTHOR
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100 Peter Meerwald.
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101 Email bug reports to pmeerw@cosy.sbg.ac.at.
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102 .SH AVAILABILITY
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103 The most recent released version of
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104 .B wm_koch_d
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105 is always available
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106 at http://www.cosy.sbg.ac.at/~pmeerw/Watermarking or via anonymous ftp from ftp.cosy.sbg.ac.at in the
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107 directory /pub/people/pmeerw/Watermarking.
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108 .SH "SEE ALSO"
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109 .BR gen_koch_sig
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110 (1),
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111 .BR wm_koch_e
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112 (1),
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113 .BR cmp_koch_sig
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114 (1)
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