1Pnmtotiffcmyk User Manual(0) Pnmtotiffcmyk User Manual(0)
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6 pnmtotiffcmyk - convert a Netpbm image into a CMYK encoded TIFF file
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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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17 This program is part of Netpbm(1).
18 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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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.
30 -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.
38 -msb2lsb,-lsb2msb
41 These options control fill order (default is -msb2lsb).
42 -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.
49 -lowdotrange,-highdotrange
52 These options set tag values that may be useful for printers.
53 -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.
58 -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.
61 -konly sets all inks to the normal black value.
63 -default,-negative
66 These options control what ink levels pnmtotiffcmyk uses to represent
67 each input color.
68 -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.
73 -default is not necessary, unless you have to countermand a -negative
75 on the same command line.
76 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.
82 The options below modify this conversion.
84 -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.
94 -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.
103 -gammap n
106 This option controls the black replacement.
107 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.
112 Values of n from 0.01 to 10 are valid.
114 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.
118 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.
124
127 pnmtotiff(1), tifftopnm(1), pnm(1)
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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.
134 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:
140 Derived by Jef Poskanzer from ras2tif.c, which is:
143 Copyright (c) 1990 by Sun Microsystems, Inc.
145 Author: Patrick J. Naughton
147 naughton@wind.sun.com
148 Permission to use, copy, modify, and distribute this software and
150 its documentation for any purpose and without fee is hereby granted,
151 provided that the above copyright notice appear in all copies and that
152 both that copyright notice and this permission notice appear in
153 supporting documentation.
154 This file is provided AS IS with no warranties of any kind. The
156 author shall have no liability with respect to the infringement of
157 copyrights, trade secrets or any patents by this file or any part
158 thereof. In no event will the author be liable for any lost revenue
159 or profits or other special, indirect and consequential damages.
160netpbm documentation 07 February 2004 Pnmtotiffcmyk User Manual(0)