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1 .\"
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2 .\" cmp_ppm.1 - the *roff document processor man page source
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3 .\"
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4 .TH cmp_ppm 1 "98/07/08" "Watermarking, Version 1.0"
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5 .SH NAME
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6 cmp_ppm \- a program to create the difference image of two PGM images
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7 .SH SYNOPSIS
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8 .B cmp_ppm
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9 [
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10 .BI \-c \ name
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11 ]
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12 [
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13 .B \-h
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14 ]
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15 [
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16 .BI \-m \ number
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17 ]
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18 [
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19 .BI \-o \ ofile
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20 ]
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21 .BI \-i \ ifile
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22 .I file
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23 .SH DESCRIPTION
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24 .B cmp_ppm
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25 is a program to create the difference image of two PPM (portable pixmap)
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26 RGB color images. To compare PGM (portable graymap) grayscale images, use
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27 the
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28 .B cmp_pgm
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29 program.
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30 .PP
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31 The color components to compare are specified with the
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32 .BI \-c \ name
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33 option, where
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34 .I name
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35 is one of the following:
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36 .TP
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37 .B red
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38 The red color component.
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39 .TP
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40 .B green
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41 The green color component.
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42 .TP
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43 .B blue
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44 The blue color component.
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45 .PP
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46 Multiple color components are allowed. Specifying only the inital letter
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47 of a color component is sufficient.
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48 Per default
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49 .B cmp_ppm
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50 compares the luminance value of the images. This operation may be
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51 selected explicitly with the
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52 .BI \-c \ luminance
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53 option.
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54 .PP
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55 If
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56 .I file
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57 or
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58 .I ofile
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59 is not specified, then standard input or standard output is
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60 used.
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61 .PP
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62 .SH OPTIONS
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63 .TP
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64 .BI \-c \ name
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65 Specifies color component(s) or luminance to compare. Default: luminance.
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66 .TP
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67 .B \-h
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68 Print a help message.
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69 .TP
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70 .BI \-i \ ifile
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71 The original image. Mandatory.
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72 .TP
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73 .BI \-m \ number
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74 Multiplication factor to magnify differences between the to
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75 original and input image.
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76 Default value: 16.
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77 .TP
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78 .BI \-o \ ofile
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79 Output image file to contain the difference image in PPM format.
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80 .TP
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81 .I file
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82 Input image that is compared against
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83 .I ifile.
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84 Default: standard input.
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85 .SH OUTPUT
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86 The difference image in PPM format is written to standard output or,
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87 optionally, to
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88 .I ofile.
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89 .SH AUTHOR
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90 Peter Meerwald.
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91 Email bug reports to pmeerw@cosy.sbg.ac.at.
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92 .SH AVAILABILITY
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93 The most recent released version of
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94 .B cmp_ppm
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95 is always available
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96 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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97 directory /pub/people/pmeerw/Watermarking.
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98 .SH "SEE ALSO"
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99 .B cmp_ppm
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100 (1)
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