1Pnmtotiffcmyk User Manual(0)                      Pnmtotiffcmyk User Manual(0)
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NAME

6       pnmtotiffcmyk - convert a Netpbm image into a CMYK encoded TIFF file
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SYNOPSIS

10       pnmtotiffcmyk          [-none|-packbits|-lzw]         [-predictor    n]
11            [-msb2lsb|-lsb2msb]      [-rowsperstrip n]       [-lowdotrange  n]
12            [-highdotrange n]      [-knormal|-konly|-kremove]      [[-default]
13       [-theta deg] [-gamma n] [-gammap n] |-negative]
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DESCRIPTION

17       This program is part of Netpbm(1).
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19       pnmtotiffcmykreads a PNM image as input and  produces  a  CMYK  encoded
20       TIFF  file  as  output.   It  optionally modifies the color balance and
21       black level, and modifies removal of CMY from under K.
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OPTIONS

25       The order of most options is not important, but options for  particular
26       conversion  algorithms  must  appear  after  the  algorithm is selected
27       (-default,-negative).  If you don't select an algorithm,  pnmtotiffcmyk
28       assumes  -default  and  the appropriate options (-theta,-gamma,-gammap)
29       can appear anywhere.
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32   -none,-packbits,-lzw,-predictor
33       Tiff files can be  compressed.   By  default,  pnmtotiffcmyk  uses  LZW
34       decompression,  but  (apparently) some readers cannot read this, so you
35       may want to select a different algorithm  (-none,-packbits).   For  LZW
36       compression,  a -predictor value of 2 forces horizontal differencing of
37       scanlines before encoding; a value of 1 forces no differencing.
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40   -msb2lsb,-lsb2msb
41       These options control fill order (default is -msb2lsb).
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44   -rowsperstrip
45       This sets the number of rows in an image strip (data in the Tiff  files
46       generated  by  this  program  is  stored in strips - each strip is com‐
47       pressed individually).  The default gives a strip size of no more  than
48       8 kb.
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51   -lowdotrange,-highdotrange
52       These options set tag values that may be useful for printers.
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55   -knormal,-kremove,-konly
56       These options control the calculation of the CMYK ink levels.  They are
57       useful only for testing and debugging the code.
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59       -kremove sets the black (K) levels to zero while leaving the other  ink
60       levels as they would be if the black level were normal.
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62       -konly sets all inks to the normal black value.
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65   -default,-negative
66       These  options  control what ink levels pnmtotiffcmyk uses to represent
67       each input color.
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69       -negative selects a simple algorithm that generates a  color  negative.
70       None  of  the following options apply to this algorithm.  The algorithm
71       is included as an example in the source code to  help  implementors  of
72       other conversions.
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74       -default  is  not necessary, unless you have to countermand a -negative
75       on the same command line.
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77       The default conversion from RGB to CMYK is as follows: The basic values
78       of  the  3  pigments  are C = 1-R, M = 1-G, Y = 1-B.  From this, pnmto‐
79       tiffcmyk chooses a black (K) level which is the minimum of those three.
80       It  then  replaces that much of the 3 pigments with the black.  I.e. it
81       substracts K from each of the basic C, M, and Y values.
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83       The options below modify this conversion.
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86   -theta deg
87       -theta provides a simple correction for any color bias that  may  occur
88       in  the printed image because, in practice, inks do not exactly comple‐
89       ment the primary colors.  It rotates the colors (before black  replace‐
90       ment) by deg degrees in the color wheel.  Unless you are trying to pro‐
91       duce unusual effects you will need to use small values.  Try generating
92       three  images  at -10, 0 (the default) and 10 degrees and see which has
93       the best color balance.
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96   -gamma n
97       -gamma applies a gamma correction to  the  black  (K)  value  described
98       above.  Specifically, instead of calculating the K value as min(C,M,Y),
99       pnmtotiffcmyk raises that value (normalised to the range 0 to 1) to the
100       nth  power.   In practice, this means that a value greater than 1 makes
101       the image lighter and a value less than 1 makes the image darker.   The
102       range of allowed values is 0.1 to 10.
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105   -gammap n
106       This option controls the black replacement.
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108       If you specify -gammap, pnmtotiffcmyk uses the specified gamma value in
109       computing how much ink to remove from the 3 pigments,  but  still  uses
110       the  regular  gamma value (-gamma option) to generate the actual amount
111       of black ink with which to replace it.
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113       Values of n from 0.01 to 10 are valid.
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115       For example, it may be best to only subtract  black  from  the  colored
116       inks  in  the  very darkest regions.  In that case, n should be a large
117       value, such as 5.
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119       As a special case, if n is -1, pnmtotiffcmyk does not remove  any  pig‐
120       ment  (but  still  adds the black ink).  This means dark areas are even
121       darker.  Furthermore, when printed, dark areas contain  a  lot  of  ink
122       which can make high contrast areas, like lettering, appear fuzzy.  It's
123       hard to see what the utility of this is.
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SEE ALSO

127       pnmtotiff(1), tifftopnm(1), pnm(1)
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AUTHOR

131       Copyright (c) 1999 Andrew Cooke (Jara Software).   Released  under  the
132       GPL  with  no  warranty.   See source or COPYRIGHT and LICENCE files in
133       distribution for full details.
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135       Much of the code uses ideas from other Netpbm programs, written by  Jef
136       Poskanzer  (thanks  go  to  him and libtiff maintainer Sam Leffler).  A
137       small section of the code - some of the tiff tag settings - is  derived
138       directly from pnmtotiff, by Jef Poskanzer, which, in turn, acknowledges
139       Patrick Naughton with the following text:
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142              Derived by Jef Poskanzer from ras2tif.c, which is:
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144              Copyright (c) 1990 by Sun Microsystems, Inc.
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146              Author: Patrick J. Naughton naughton@wind.sun.com
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148              Permission to use, copy, modify, and  distribute  this  software
149              and  its documentation for any purpose and without fee is hereby
150              granted, provided that the above copyright notice appear in  all
151              copies  and  that both that copyright notice and this permission
152              notice appear in supporting documentation.
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154              This file is provided AS IS with no warranties of any kind.  The
155              author  shall have no liability with respect to the infringement
156              of copyrights, trade secrets or any patents by this file or  any
157              part  thereof.   In  no  event will the author be liable for any
158              lost revenue or profits or other special,  indirect  and  conse‐
159              quential damages.
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164netpbm documentation           07 February 2004   Pnmtotiffcmyk User Manual(0)
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