pnmtotiff - convert a PNM image to a TIFF file
SYNOPSIS
pnmtotiff [-none|-packbits|-lzw|-g3|-g4] [-2d] [-fill]
[-predictor n] [-msb2lsb|-lsb2msb] [-rowsperstrip n]
[-minisblack] [pnmfile]
Minimum unambiguous abbreviations of options are accept
able.
DESCRIPTION
Reads a PNM image as input. Produces a TIFF file as out
put.
OPTIONS
By default, pnmtotiff creates a TIFF file with no compres
sion. This is your best bet most of the time. If you
want to try another compression scheme or tweak some of
the other even more obscure output options, there are a
number of flags to play with.
Actually, the best default would be to use LZW compres
sion, which is what pnmtotiff used to do by default. How
ever, the Tiff library no longer does LZW compression due
to concerns with violating Unisys's patent on LZW compres
sion.
The -none, -packbits, -lzw, -g3, and -g4 options are used
to override the default and set the compression scheme
used in creating the output file. The CCITT Group 3 and
Group 4 compression algorithms can only be used with
bilevel data. -lzw doesn't really work because the Tiff
library doesn't do LZW compression. It used to, but its
developers removed the function out of concern about vio
lating Unisys's patent. This option remains in case you
use a Tiff library that cooperates, now or in the future.
The -2d and -fill options are meaningful only with Group 3
compression: -2d requests 2-dimensional encoding, while
-fill requests that each encoded scanline be zero-filled
to a byte boundry. The -predictor option is only meaning
ful with LZW compression: a predictor value of 2 causes
each scanline of the output image to undergo horizontal
differencing before it is encoded; a value of 1 forces
each scanline to be encoded without differencing.
By default, pnmtotiff creates a TIFF file with msb-to-lsb
fill order. The -msb2lsb and -lsb2msb options are used to
override the default and set the fill order used in creat
ing the file.
The -rowsperstrip option can be used to set the number of
By default, the output file has the number of rows per
strip set to a value that will ensure each strip is no
more than 8 kilobytes long.
The -minisblack option forces the output image to have a
"minimum is black" photometric even when using Group 3 or
Group 4 compression, in which case CCITT fax standards say
the proper photometric is "minimum is white."
Without the -minisblack option, pnmtotiff follows the
standard. This usually results in better compression and
is generally preferred for bilevel coding.
Before February 2001, pnmtotiff always produced "minimum
is black," due to a bug. In either case, pnmtotiff sets
the photometric interpretation tag in the TIFF output
according to which photometric is actually used.
NOTES
There are myriad variations of the TIFF format, and this
program generates only a few of them. pnmtotiff creates a
grayscale TIFF file if its input is a PBM (monochrome) or
PGM (grayscale) file. If the input is a PPM (color) file
and there are 256 colors or fewer, pnmtotiff generates a
color palette TIFF file. If there are more colors than
that, pnmtotiff generates an RGB (not RGBA) single plane
TIFF file. Use pnmtotiffcmyk to generate the cyan-
magenta-yellow-black ink color separation TIFF format.
SEE ALSO
tifftopnm(1), pnmtotiffcmyk(1), pnm(5)
AUTHOR
Derived by Jef Poskanzer from ras2tiff.c, which is Copy
right (c) 1990 by Sun Microsystems, Inc. Author: Patrick
J. Naughton (naughton@wind.sun.com).
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