pnmtotiffcmyk  -  convert  a 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 bal­
       ance 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  algo­
       rithm  is selected then -default is assumed and the appro­
       priate options  (-theta,-gamma,-gammap)  can  appear  any­
       where.

       -none,-packbits,-lzw,-predictor
              Tiff  files  can  be  compressed.   By  default LZW
              decompression is used, but (apparently) some  read­
              ers  cannot  read this, so you may want to select a
              different  algorithm  (-none,-packbits).   For  LZW
              compression,  a  -predictor value of 2 forces hori­
              zontal 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.

              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 conver­
              sion  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 correc­
              tion  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

              can  make  high  contrast  areas,  like  lettering,
              appear fuzzy.

              By default, when -gammap is not given on  the  com­
              mand 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 sig­
              nificantly.

              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, acknowl­
       edges 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

              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, indi­
              rect and consequential damages.


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