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



NAME
       pnmtotiffcmyk - convert a Netpbm image into a CMYK encoded TIFF file


SYNOPSIS
       pnmtotiffcmyk       [-none|-packbits|-lzw]       [-predictor n]      [-msb2lsb|-lsb2msb]      [-rowsperstrip n]
            [-lowdotrange n]      [-highdotrange  n]       [-knormal|-konly|-kremove]       [[-default]  [-theta  deg]
       [-gamma n] [-gammap n] |-negative]


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  dif-
       ferencing.


   -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 con-
       versions.

       -default is not necessary, unless you have to countermand 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
       values.  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 COPY-
       RIGHT 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, 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 naughtonATwind.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 February 2004   Pnmtotiffcmyk User Manual(0)