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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)