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1 .\"
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2 .\" wm_cox_d.1 - the *roff document processor man page source
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3 .\"
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4 .TH wm_cox_d 1 "98/07/05" "Watermarking, Version 1.0"
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5 .SH NAME
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6 .B wm_cox_d
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7 \- a program to extract a signature from the DCT coefficients of a watermarked image
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8 .SH SYNOPSIS
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9 .B wm_cox_d
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10 [
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11 .BI \-a \ number
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12 ]
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13 [
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14 .B \-h
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15 ]
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16 [
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17 .BI \-i \ ifile
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18 ]
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19 [
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20 .BI \-n \ number
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21 ]
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22 [
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23 .BI \-o \ ofile
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24 ]
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25 [
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26 .BI \-q \ number
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27 ]
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28 [
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29 .BI \-v \ number
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30 ]
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31 .br
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32 .BI \-s \ sfile
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33 .I file
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34 .SH DESCRIPTION
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35 .B wm_cox_d
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36 is a program to extract a signature from the DCT coefficients of the watermarked image
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37 .I file.
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38 The
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39 .B cmp_cox_sig
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40 program is used to test the extracted signature against the original signature.
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41 The input image is in PGM (portable graymap) format.
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42 .PP
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43 If
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44 .I file
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45 or
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46 .I ofile
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47 is not specified, then standard input or standard output is
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48 used.
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49 .PP
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50 .B gen_cox_sig
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51 is used to generate a signature file,
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52 .B wm_cox_e
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53 embeds the signature into an image.
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54 .PP
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55 Please refer to Ingemar J. Cox's paper "Secure Spread Spectrum
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56 Watermarking for Multimedia", 1995, to get an idea about the algorithm.
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57 .PP
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58 .SH OPTIONS
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59 .TP
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60 .BI \-a \ number
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61 Alpha factor that determines embedding strength of the signature.
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62 Allows to override the setting in the signature file.
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63 .TP
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64 .B \-h
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65 Print a help message.
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66 .TP
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67 .BI \-i \ ifile
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68 The original image.
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69 .TP
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70 .BI \-o \ ofile
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71 Output watermarked image to the specified
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72 .I file
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73 instead of standard output.
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74 .TP
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75 .BI \-q \ number
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76 Set quantization/quality factor. Overrides the setting in the signature
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77 file.
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78 .TP
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79 .BI \-v \ number
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80 Verbosity level. Default value: 0.
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81 .TP
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82 .BI \-s \ sfile
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83 The signature file to embed into the input image. See
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84 .B gen_cox_sig
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85 (1) for a description of the file format. Mandatory parameter.
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86 .IR file
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87 Input image in PGM format to sign (watermark). Default: standard input.
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88 .TP
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89 .I
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90 The watermarked image file in PGM format.
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91 .PP
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92 .SH OUTPUT
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93 The signed (watermarked) image in PGM format is written to standard output
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94 or ,optionally, to
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95 .I ofile.
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96 The embedding process may take some time on large images since the DCT
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97 is performed on the whole image in one step (not block-wise).
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98 .PP
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99 .PP
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100 The output file has the following format:
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101 .TP
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102 .B CXSG
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103 Magic to identify file type.
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104 .TP
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105 .I number
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106 The length of the signature in bits.
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107 .TP
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108 .I number
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109 The alpha factor (embedding strength).
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110 .TP
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111 .I number
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112 The quantization/quality factor.
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113 .TP
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114 .I numbers
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115 The actual normal distributed signature values, one per line.
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116 .PP
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117 .SH AUTHOR
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118 Peter Meerwald.
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119 Email bug reports to pmeerw@cosy.sbg.ac.at.
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120 .SH AVAILABILITY
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121 The most recent released version of
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122 .B wm_cox_d
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123 is always available
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124 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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125 directory /pub/people/pmeerw/Watermarking.
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126 .SH "SEE ALSO"
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127 .BR gen_cox_sig
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128 (1),
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129 .BR wm_cox_e
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130 (1),
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131 .BR cmp_cox_sig
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132 (1)
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