Provided by: netpbm_10.0-15.4_amd64 
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)