tifftopnm - convert a TIFF file into a portable anymap
SYNOPSIS
tifftopnm [--alphaout={alpha-filename,-}] [--headerdump]
tiff-filename
DESCRIPTION
Reads a TIFF file as input. Produces a portable anymap as
output. The type of the output file depends on the input
file - if it's black & white, generates a pbm file; if
it's grayscale, generates a pgm file; otherwise, a ppm
file. The program tells you which type it is writing.
This program cannot read every possible TIFF file -- there
are myriad variations of the TIFF format. However, it
does understand monochrome and gray scale, RGB, RGBA
(red/green/blue with alpha channel), CMYK (Cyan-Magenta-
Yellow-Black ink color separation), and color palette TIFF
files. An RGB file can have either single plane (inter
leaved) color or multiple plane format. The program reads
1-8 and 16 bit-per-sample input, the latter in either
bigendian or littlendian encoding. Tiff directory infor
mation may also be either bigendian or littendian.
One reason this program isn't as general as TIFF programs
often are is that it does not use the TIFFRGBAImageGet()
function of the TIFF library to read TIFF files. Rather,
it uses the more primitive TIFFReadScanLine() function and
decodes it itself.
There is no fundamental reason that this program could not
read other kinds of TIFF files; the existing limitations
are mainly because no one has asked for more.
The PNM output has the same maxval as the Tiff input,
except that if the Tiff input is colormapped (which
implies a maxval of 65535) the PNM output has a maxval of
255. Though this may result in lost information, such
input images hardly ever actually have more color resolu
tion than a maxval of 255 provides and people often cannot
deal with PNM files that have maxval > 255. By contrast,
a non-colormapped Tiff image that doesn't need a maxval >
255 doesn't have a maxval > 255, so when we see a non-col
ormapped maxval > 255, we take it seriously and produce a
matching output maxval.
The tiff-filename argument names the regular file that
contains the Tiff image. You cannot use Standard Input or
any other special file because the Tiff library must be
able to perform seeks on it.
--alphaout=alpha-filename
tifftopnm creates a PGM (portable graymap) file
containing the alpha channel values in the input
image. If the input image doesn't contain an alpha
channel, the alpha-filename file contains all zero
(transparent) alpha values. If you don't specify
--alphaout, tifftopnm does not generate an alpha
file, and if the input image has an alpha channel,
tifftopnm simply discards it.
If you specify - as the filename, tifftopnm writes
the alpha output to Standard Output and discards
the image.
See pnmcomp(1) for one way to use the alpha output
file.
--headerdump
Dump TIFF file information to stderr. This infor
mation may be useful in debugging TIFF file conver
sion problems.
All options can be abbreviated to their shortest unique
prefix.
SEE ALSO
pnmtotiff(1), pnmtotiffcmyk(1), pnmcomp(1), pnm(5)
AUTHOR
Derived by Jef Poskanzer from tif2ras.c, which is Copy
right (c) 1990 by Sun Microsystems, Inc. Author: Patrick
J. Naughton (naughton@wind.sun.com).
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