tifftopnm(1) - man - phpMan

Che Dong

tifftopnm(1) General Commands Manual tifftopnm(1)

NAME
tifftopnm - convert a TIFF file into a portable anymap

SYNOPSIS
tifftopnm [-alphaout={alpha-filename,-}] [-headerdump] [-respectfillorder] [tiff-filename]

You may abbreviate any option to its shortest unique prefix. You may use two hyphens instead
of one in options. You may separate an option and its value either by an equals sign or
white space.

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 (interleaved) 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 information 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 col‐
ormapped (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 reso‐
lution 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-colormapped maxval > 255, we take it seri‐
ously and produce a matching output maxval.

The tiff-filename argument names the regular file that contains the Tiff image. If you spec‐
ify "-" or don't specify this argument, tfftopnm uses Standard Input. In either case, the
file must be seekable. That means no pipe, but any regular file is fine.

OPTIONS
-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-file‐
name file contains all zero (transparent) alpha values. If you don't specify -al‐‐
phaout, 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.

-respectfillorder
By default, tifftopnm ignores the "fillorder" tag in the TIFF input, which means it
may incorrectly interpret the image. To make it follow the spec, use this option.
For a lengthy but engaging discussion of why tifftopnm works this way and how to use
the -respectfillorder option, see the note on fillorder below.

-headerdump
Dump TIFF file information to stderr. This information may be useful in debugging
TIFF file conversion problems.

All options can be abbreviated to their shortest unique prefix.

NOTES
Fillorder
There is a piece of information in the header of a TIFF image called "fillorder." The TIFF
specification quite clearly states that this value tells the order in which bits are arranged
in a byte in the description of the image's pixels. There are two options, assuming that the
image has a format where more than one pixel can be represented by a single byte: 1) the byte
is filled from most signficant bit to least signficant bit going left to right in the image;
and 2) the opposite.

However, there is confusion in the world as to the meaning of fillorder. Evidence shows that
some people believe it has to do with byte order when a single value is represented by two
bytes.

These people cause TIFF images to be created that, while they use a MSB-to-LSB fillorder,
have a fillorder tag that says they used LSB-to-MSB. A program that properly interprets a
TIFF image will not end up with the image that the author intended in this case.

For a long time, tifftopnm did not understand fillorder itself and assumed the fillorder was
MSB-to-LSB regardless of the fillorder tag in the TIFF header. And as far as I know, there
is no legitimate reason to use a fillorder other than MSB-to-LSB. So users of tifftopnm were
happily using those TIFF images that had incorrect fillorder tags.

So that those users can continue to be happy, tifftopnm today continues to ignore the fil‐
lorder tag unless you tell it not to. (It does, however, warn you when the fillorder tag
does not say MSB-to-LSB that the tag is being ignored).

If for some reason you have a TIFF image that actually has LSB-to-MSB fillorder, and its fil‐
lorder tag correctly indicates that, you must use the -respectfillorder option on tifftopnm
to get proper results.

Examples of incorrect TIFF images are at ftp://weather.noaa.gov. They are apparently created
by a program called faxtotiff.

This note was written on January 1, 2002.

SEE ALSO
pnmtotiff(1), pnmtotiffcmyk(1), pnmcomp(1), pnm(5)

AUTHOR
Derived by Jef Poskanzer from tif2ras.c, which is Copyright (c) 1990 by Sun Microsystems,
Inc. Author: Patrick J. Naughton (naughton AT wind.com).

02 April 2000 tifftopnm(1)