Section: User Commands (1)
Updated: 9 December 1999
pnmtotiffcmyk [Compargs][Tiffargs][Convargs][ pnmfile ]
:Compargs[-none|-packbits|-lzw [-predictor n]]
:Tiffargs[-msb2lsb|-lsb2msb] [-rowsperstrip n]
[-lowdotrange n] [-highdotrange n]
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.
-kremove sets the black (K) layer to zero while -konly sets all inks to the black value.
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.
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.
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:
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