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Pnmtotiffcmyk User Manual(0)					     Pnmtotiffcmyk User Manual(0)

NAME
       pnmtotiffcmyk - convert a Netpbm image into a CMYK encoded TIFF file

SYNOPSIS
       pnmtotiffcmyk	   [-none|-packbits|-lzw]	[-predictor  n]       [-msb2lsb|-lsb2msb]
	    [-rowsperstrip  n]	     [-lowdotrange   n]        [-highdotrange	n]	  [-knor-
       mal|-konly|-kremove]	 [[-default] [-theta deg] [-gamma n] [-gammap n] |-negative]

DESCRIPTION
       This program is part of Netpbm(1)

       pnmtotiffcmykreads  a  PNM image as input and produces a CMYK encoded TIFF file as output.
       It optionally modifies the color balance and black level, and modifies removal of CMY from
       under K.

OPTIONS
       The  order  of  most options is not important, but options for particular conversion algo-
       rithms must appear after the algorithm is selected  (-default,-negative).   If  you  don't
       select	an   algorithm,  pnmtotiffcmyk	assumes  -default  and	the  appropriate  options
       (-theta,-gamma,-gammap) can appear anywhere.

   -none,-packbits,-lzw,-predictor
       Tiff files can be compressed.  By  default,  pnmtotiffcmyk  uses  LZW  decompression,  but
       (apparently)  some  readers  cannot read this, so you may want to select a different algo-
       rithm (-none,-packbits).  For LZW compression, a -predictor value of 2  forces  horizontal
       differencing of scanlines before encoding; a value of 1 forces no differencing.

   -msb2lsb,-lsb2msb
       These options control fill order (default is -msb2lsb).

   -rowsperstrip
       This  sets  the number of rows in an image strip (data in the Tiff files generated by this
       program is stored in strips - each strip is compressed individually).  The default gives a
       strip size of no more than 8 kb.

   -lowdotrange,-highdotrange
       These options set tag values that may be useful for printers.

   -knormal,-kremove,-konly
       These  options  control	the calculation of the CMYK ink levels.  They are useful only for
       testing and debugging the code.

       -kremove sets the black (K) levels to zero while leaving the  other  ink  levels  as  they
       would be if the black level were normal.

       -konly sets all inks to the normal black value.

   -default,-negative
       These options control what ink levels pnmtotiffcmyk uses to represent each input color.

       -negative selects a simple algorithm that generates a color negative.  None of the follow-
       ing options apply to this algorithm.  The algorithm is  included  as  an  example  in  the
       source code to help implementors of other conversions.

       -default  is not necessary, unless you have to countermand a -negative on the same command
       line.

       The default conversion from RGB to CMYK is as follows: The basic values of the 3  pigments
       are  C  = 1-R, M = 1-G, Y = 1-B.  From this, pnmtotiffcmyk chooses a black (K) level which
       is the minimum of those three.  It then replaces that much of  the  3  pigments	with  the
       black.  I.e. it substracts K from each of the basic C, M, and Y values.

       The options below modify this conversion.

   -theta deg
       -theta provides a simple correction for any color bias that may occur in the printed image
       because, in practice, inks do not exactly complement the primary colors.  It  rotates  the
       colors  (before black replacement) by deg degrees in the color wheel.  Unless you are try-
       ing to produce unusual effects you will need to use small values.   Try	generating  three
       images at -10, 0 (the default) and 10 degrees and see which has the best color balance.

   -gamma n
       -gamma  applies	a gamma correction to the black (K) value described above.  Specifically,
       instead of calculating the K value as min(C,M,Y), pnmtotiffcmyk raises  that  value  (nor-
       malised	to  the  range	0  to  1) to the nth power.  In practice, this means that a value
       greater than 1 makes the image lighter and a value less than 1  makes  the  image  darker.
       The range of allowed values is 0.1 to 10.

   -gammap n
       This option controls the black replacement.

       If you specify -gammap, pnmtotiffcmyk uses the specified gamma value in computing how much
       ink to remove from the 3 pigments, but still uses the regular gamma value (-gamma  option)
       to generate the actual amount of black ink with which to replace it.

       Values of n from 0.01 to 10 are valid.

       For example, it may be best to only subtract black from the colored inks in the very dark-
       est regions.  In that case, n should be a large value, such as 5.

       As a special case, if n is -1, pnmtotiffcmyk does not remove any pigment (but  still  adds
       the  black  ink).  This means dark areas are even darker.  Furthermore, when printed, dark
       areas contain a lot of ink which can make high  contrast  areas,  like  lettering,  appear
       fuzzy.  It's hard to see what the utility of this is.

SEE ALSO
       pnmtotiff(1) , tifftopnm(1) , pnm(5)

AUTHOR
       Copyright (c) 1999 Andrew Cooke (Jara Software).  Released under the GPL with no warranty.
       See source or COPYRIGHT and LICENCE files in distribution for full details.

       Much of the code uses ideas from other Netpbm programs, written by Jef  Poskanzer  (thanks
       go  to him and libtiff maintainer Sam Leffler).	A small section of the code - some of the
       tiff tag settings - is derived directly from pnmtotiff, by Jef Poskanzer, which, in  turn,
       acknowledges Patrick Naughton with the following text:

       Derived by Jef Poskanzer from ras2tif.c, which is:

       Copyright (c) 1990 by Sun Microsystems, Inc.

       Author: Patrick J. Naughton
       naughton@wind.sun.com

       Permission to use, copy, modify, and distribute this software and
       its documentation for any purpose and without fee is hereby granted,
       provided that the above copyright notice appear in all copies and that
       both that copyright notice and this permission notice appear in
       supporting documentation.

       This file is provided AS IS with no warranties of any kind.  The
       author shall have no liability with respect to the infringement of
       copyrights, trade secrets or any patents by this file or any part
       thereof.  In no event will the author be liable for any lost revenue
       or profits or other special, indirect and consequential damages.

netpbm documentation			 07 February 2004	     Pnmtotiffcmyk User Manual(0)
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