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       pnmtotiffcmyk - convert 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.   Optionally  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  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

              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.

              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 tested.

              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.

              -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

              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


       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

              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)