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NAME

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

SYNOPSIS

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

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

       Tiffargs:
              [-msb2lsb|-lsb2msb] [-rowsperstrip n]
              [-lowdotrange n] [-highdotrange n]
              [-knormal|-konly|-kremove]

       Convargs:
              [[-default][Defargs]|-negative]

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

DESCRIPTION

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

OPTIONS

       The order of most  options  is  not  important,  but  options  for  particular  conversion
       algorithms  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.

       -none,-packbits,-lzw,-predictor
              Tiff  files  can  be  compressed.   By  default  LZW  decompression  is  used,  but
              (apparently) some readers cannot read this, so you may want to select  a  different
              algorithm  (-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 flags 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.  They have not been
              tested.

       -knormal,-kremove,-konly
              These options modify the values written to  the  Tiff  file  after  the  conversion
              calculations (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
              value.

       -default,-negative
              -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
              conversion 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
              explanation clearer.

       -theta deg
              The  basic  conversion  from  RGB  to  CMY  uses C = 1-R, M = 1-G, Y = 1-B.  -theta
              provides 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
              balance.

       -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
              (normalised  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
              fuzziness 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.

BUGS

       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).

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 (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
              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.

                                         9 December 1999                         pnmtotiffcmyk(1)