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pnmtotiffcmyk(1)								 pnmtotiffcmyk(1)

       pnmtotiffcmyk - convert a a portable anymap into a CMYK encoded TIFF file

       pnmtotiffcmyk [Compargs][Tiffargs][Convargs][ pnmfile ]

	      [-none|-packbits|-lzw [-predictor n]]

	      [-msb2lsb|-lsb2msb] [-rowsperstrip n]
	      [-lowdotrange n] [-highdotrange n]


	      [-theta deg] [-gamma n] [-gammap -1|-gammap n]

       Reads  a  portable anymap as input.  Produces a CMYK encoded TIFF file as output.  Option-
       ally modifies the colour balance and black level, and removes CMY from under K.

       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 no algorithm
       is selected then -default is assumed and the appropriate  options  (-theta,-gamma,-gammap)
       can appear anywhere.

	      Tiff  files  can	be compressed.	By default LZW decompression is used, but (appar-
	      ently) 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 hori-
	      zontal differencing of scanlines before encoding; a value of 1 forces no differenc-

	      These flags control fill order (default is -msb2lsb).

	      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.

	      These  options  set tag values that may be useful for printers.  They have not been

	      These options modify the values written to the Tiff file after the conversion  cal-
	      culations  (described  below)  are completed.  They are useful only for testing and
	      debugging the code.

	      -kremove sets the black (K) layer to zero while -konly sets all inks to  the  black

	      -negative selects a simple algorithm that generates a colour negative.  None of the
	      following options apply to this algorithm, which is included as an example  in  the
	      source  to  help implementors of other conversions.  -default is not needed, unless
	      it is used to countermand a -negative on the same command line.  The  default  con-
	      version from RGB to CMYK can be modified by altering the options listed below.

	      The CMYKTiff web site includes tests on the conversion parameters.  The test images
	      illustrate the command line options in practice and may make the following explana-
	      tion clearer.

       -theta deg
	      The  basic  conversion from RGB to CMY uses C = 1-R, M = 1-G, Y = 1-B.  -theta pro-
	      vides a simple correction for any colour bias that may occur in the  printed  image
	      because,	in  practice,  inks  do  not  exactly complement the primary colours.  It
	      rotates the colours by the amount given (deg) in degrees.  Unless you are trying to
	      produce  unusual	effects  you  will need to use small values (try generating three
	      images at -10, 0 (the default) and 10 degrees and seeing which has the best  colour

       -gamma n
	      The black (K) component of the image is calculated as min(C,Y,M).  -gamma applies a
	      gamma correction to this level.  In other words, the final black level is  K  (nor-
	      malised  to the range 0 to 1) raised 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 removal of CMY under K.	If n is -1 then no removal occurs
	      and C, M, Y and K are calculated as above.  This means  that,  when  printed,  dark
	      areas  contain  all  four inks, which can make high contrast areas, like lettering,
	      appear fuzzy.

	      By default, when -gammap is not given on the command line, the colours are  reduced
	      in  dark	areas by subtracting the black level.  The value subtracted is calculated
	      with the same gamma correction given by -gamma.  Hopefully this will reduce  fuzzi-
	      ness without changing the appearance of the image significantly.

	      If  -gammap n is given, with n between 0.01 and 10, then black is still subtracted,
	      but the subtracted value is calculated using n rather than any value supplied  with
	      -gamma.	For example, it may be best to only subtract black from the coloured inks
	      in the very darkest regions.  In that case, n should be a large value, such as 5.

       This program is not self-contained.  It must be used  with  NetPbm  and	libtiff  must  be
       available (libtiff is included in the 1mar94 release of NetPbm).

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

       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 (and man page!) uses ideas  from  other  pnm  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  copy-
	      right notice appear in all copies and that both that copyright notice and this per-
	      mission 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 dam-

					 9 December 1999			 pnmtotiffcmyk(1)
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