pnmtotiffcmyk

pnmtotiffcmyk(1)            General Commands Manual           pnmtotiffcmyk(1)

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 (-de-
       fault,-negative).  If no algorithm is selected then -default is assumed
       and the appropriate 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 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  differ-
              encing of scanlines before encoding; a value of 1 forces no dif-
              ferencing.

       -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  algo-
              rithm, which is included as an example in the source to help im-
              plementors 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  al-
              tering the options listed below.

              The  CMYKTiff  web site includes tests on the conversion parame-
              ters.  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 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.

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 conse-
              quential damages.

                                9 December 1999               pnmtotiffcmyk(1)