Pnmtotiffcmyk User Manual(0)       Pnmtotiffcmyk User Manual(0)



Table Of Contents


NAME
       pnmtotiffcmyk  -  convert  a  Netpbm  image  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
       This program is part of Netpbm(1).

       pnmtotiffcmykreads a PNM image as input and  produces  a
       CMYK  encoded  TIFF file as output.  It optionally modi-
       fies the color balance and  black  level,  and  modifies
       removal of 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 you
       don't  select  an   algorithm,   pnmtotiffcmyk   assumes
       -default      and      the      appropriate      options
       (-theta,-gamma,-gammap) can appear anywhere.


   -none,-packbits,-lzw,-predictor
       Tiff files can be compressed.  By default, pnmtotiffcmyk
       uses  LZW  decompression,  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 options 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.


   -knormal,-kremove,-konly
       These  options  control  the calculation of the CMYK ink
       levels.  They are useful only for testing and  debugging
       the code.

       -kremove sets the black (K) levels to zero while leaving
       the other ink levels as they would be if the black level
       were normal.

       -konly sets all inks to the normal black value.


   -default,-negative
       These options control what ink levels pnmtotiffcmyk uses
       to represent each input color.

       -negative selects a simple algorithm  that  generates  a
       color  negative.  None of the following options apply to
       this algorithm.  The algorithm is included as an example
       in the source code to help implementors of other conver-
       sions.

       -default is not necessary, unless you have  to  counter-
       mand a -negative on the same command line.

       The  default  conversion from RGB to CMYK is as follows:
       The basic values of the 3 pigments are C = 1-R, M = 1-G,
       Y  =  1-B.  From this, pnmtotiffcmyk chooses a black (K)
       level which is the minimum  of  those  three.   It  then
       replaces  that  much  of  the 3 pigments with the black.
       I.e. it substracts K from each of the basic C, M, and  Y
       values.

       The options below modify this conversion.


   -theta deg
       -theta  provides  a simple correction for any color bias
       that may occur in the printed image  because,  in  prac-
       tice, inks do not exactly complement the primary colors.
       It rotates the colors (before black replacement) by  deg
       degrees  in  the  color wheel.  Unless you are trying to
       produce unusual effects you will need to use small  val-
       ues.   Try  generating  three  images  at  -10,  0  (the
       default) and 10 degrees and see which has the best color
       balance.


   -gamma n
       -gamma applies a gamma correction to the black (K) value
       described above.  Specifically, instead  of  calculating
       the  K  value  as  min(C,M,Y), pnmtotiffcmyk raises that
       value (normalised to the range 0 to 1) 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 black replacement.

       If you specify -gammap, pnmtotiffcmyk uses the specified
       gamma value in computing how much ink to remove from the
       3 pigments, but  still  uses  the  regular  gamma  value
       (-gamma  option)  to generate the actual amount of black
       ink with which to replace it.

       Values of n from 0.01 to 10 are valid.

       For example, it may be best to only subtract black  from
       the  colored  inks in the very darkest regions.  In that
       case, n should be a large value, such as 5.

       As a special case, if n is -1,  pnmtotiffcmyk  does  not
       remove any pigment (but still adds the black ink).  This
       means dark areas are  even  darker.   Furthermore,  when
       printed,  dark areas contain a lot of ink which can make
       high contrast areas, like lettering, appear fuzzy.  It's
       hard to see what the utility of this is.


SEE ALSO
       pnmtotiff(1), tifftopnm(1), pnm(1)


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 uses ideas from other Netpbm  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 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.




netpbm documentation    07 FebruaryPnmtotiffcmyk User Manual(0)
