tifftopnm man page on Knoppix

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tifftopnm(1)							  tifftopnm(1)

NAME
       tifftopnm - convert a TIFF file into a portable anymap

SYNOPSIS
       tifftopnm  [-alphaout={alpha-filename,-}]  [-headerdump]	 [-respectfil‐
       lorder] [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	 TIFF‐
       ReadScanLine() 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 informa‐
       tion, such input images hardly ever actually have more color resolution
       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	seriously  and
       produce a matching output maxval.

       The  tiff-filename  argument  names  the regular file that contains the
       Tiff image.  If	you  specify  "-"  or  don't  specify  this  argument,
       tfftopnm	 uses  Standard	 Input. In either case, the file must be seek‐
       able.  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-filename  file  con‐
	      tains 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.

       -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	repre‐
       sented 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 fil‐
       lorder.	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 fillorder tag unless you tell it not to.	(It does, how‐
       ever, 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 fillorder 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@wind.sun.com).

				 02 April 2000			  tifftopnm(1)
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