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Tifftopnm User Manual(0)			      Tifftopnm	User Manual(0)

NAME
       tifftopnm - convert a TIFF file into a PNM image

SYNOPSIS
       tifftopnm

       [-alphaout={alpha-filename,-}]  [-headerdump]  [-verbose] [-respectfil-
       lorder] [-byrow]	[-orientraw] [tiff-filename]

DESCRIPTION
       This program is part of Netpbm(1).

       tifftopnm reads a TIFF file as input and	produces a PNM image  as  out-
       put.   The  type	of the output file depends on the input	file - if it's
       black and white,	tifftopnm generates a PBM image; if it's grayscale, it
       generates a PGM image; otherwise, the output is PPM.  The program tells
       you which type it is writing.

       If the TIFF file	contains  multiple  images  (multiple  "directories"),
       tifftopnm  generates  a	multi-image  PNM output	stream.	 Before	Netpbm
       10.27 (March 2005), however, it would just ignore all but the first in-
       put image.

       The tiff-filename argument names	the file that contains the Tiff	image.
       If you specify "-" or don't specify this	argument, tifftopnm uses Stan-
       dard Input.

       In  either  case,  before  Netpbm  10.70	(March 2015), the file must be
       seekable.  That means no	pipe, but any regular file is fine.   In  cur-
       rent  Netpbm, the file need not be seekable, but	if it isn't, tifftopnm
       creates a temporary regular file	containing the entire  image,  so  you
       must have resources for that (and it may	defeat your reason for using a
       pipe).

   TIFF	Capability
       pamtotiff uses the Libtiff.org TIFF library (or whatever	equivalent you
       provide)	 to  interpret the TIFF	input.	So the set of files it is able
       to interpret is determined mostly by that library.

       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  transparency  channel),
       CMYK  (Cyan-Magenta-Yellow-Black	 ink color separation),	and color pal-
       ette 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 en-
       coding.	 Tiff  directory  information  may also	be either bigendian or
       littlendian.

       There are many TIFF formats that	tifftopnm can read only	if  the	 image
       is  small  enough  to fit in memory.  tifftopnm uses the	TIFF library's
       TIFFRGBAImageGet() function to process the TIFF image  if  it  can  get
       enough memory for TIFFRGBAImageGet() to store the whole image in	memory
       at once (that's what TIFFRGBAImageGet() does).  If not, tifftopnm  uses
       a  more primitive row-by-row conversion strategy	using the raw data re-
       turned by TIFFReadScanLine() and	native intelligence.  That native  in-
       telligence  does	 not  know as many formats as TIFFRGBAImageGet() does.
       And certain compressed formats simply cannot be read with TIFFReadScan-
       Line().

       Before  Netpbm  10.11  (October 2002), tifftopnm	never used TIFFRGBAIm-
       ageGet(), so it could not interpret many	of the formats it  can	inter-
       pret today.

       There  is  no fundamental reason	that this program could	not read other
       kinds of	TIFF files even	when they don't	fit in	memory	all  at	 once.
       The existing limitations	are mainly because no one has asked for	more.

   Output Image
       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  im-
       age  that  doesn't  need	a maxval > 255 doesn't have a maxval > 255, so
       when tifftopnm sees a non-colormapped maxval > 255, it takes  it	 seri-
       ously and produces a matching output maxval.

       Another exception is where the TIFF maxval is greater than 65535, which
       is the maximum allowed by the Netpbm formats.  In that case,  tifftopnm
       uses  a	maxval	of 65535, and you lose some information	in the conver-
       sion.

OPTIONS
       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.

       -alphaout=alpha-filename
	      tifftopnm	creates	a PGM file containing the alpha	channel	values
	      in the input image.  If the input	image doesn't contain a	trans-
	      parency channel,	the  alpha-filename  file  contains  all  zero
	      (transparent)  transparency  values.   If	you don't specify -al-
	      phaout,

	      tifftopnm	does not generate a transparency file, and if the  in-
	      put image	has an transparency channel, tifftopnm simply discards
	      it.

	      If you specify - as the filename,	tifftopnm writes the transpar-
	      ency output to Standard Output and discards the image.

	      See pamcomp(1) for one way to use	the transparency 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 en-
	      gaging discussion	of why tifftopnm works this way	and how	to use
	      the -respectfillorder option, see	the note on fillorder below.

       -byrow This option can make tifftopnm run faster.

	      tifftopnm	 has  two  ways	to do the conversion from Tiff to PNM,
	      using respectively two facilities	of the TIFF library:

       Whole Image
	      Decode the entire	image into memory at once,  using  TIFFRGBAIm-
	      ageGet(),	then convert to	PNM and	output row by row.

       Row By Row
	      Read,  convert, and output one row at a time using TIFFReadScan-
	      line()

	      Whole Image is preferable	because	the Tiff library does more  of
	      the  work,  which	 means	it understands more of the Tiff	format
	      possibilities now	and in the future.  Also, some compressed TIFF
	      formats don't allow you to extract an individual row.

	      Row  By Row uses far less	memory,	which means with large images,
	      it can run in environments where Whole Image cannot and may also
	      run faster.  And because Netpbm code does	more of	the work, it's
	      possible that it can be more flexible or at  least  give	better
	      diagnostic information if	there's	something wrong	with the TIFF.

	      The  Netpbm native code may do something correctly that the TIFF
	      library does incorrectly,	or vice	versa.

	      In Netpbm, we stress function over performance, so by default we
	      try Whole	Image first, and if we can't get enough	memory for the
	      decoded image or TIFFRGBAImageGet() fails, we fall back  to  Row
	      By  Row.	 But  if you specify the -byrow	option,	tifftopnm will
	      not attempt Whole	Image.	If Row By Row does not work, it	simply
	      fails.

	      See  Color Separation (CMYK) TIFFs <#cmyk>  for a	description of
	      one way Row By Row makes a significant difference	 in  your  re-
	      sults.

	      Whole  Image  costs you precision	when your TIFF image uses more
	      than 8 bits per sample.  TIFFRGBAImageGet() converts the samples
	      to 8 bits.  tifftopnm then scales	them back to maxval 65535, but
	      the lower	8 bits of information is gone.

	      In many versions of the TIFF  library,  TIFFRGBAImageGet()  does
	      not  correctly interpret TIFF files in which the raster orienta-
	      tion is column-major (i.e. a row of the raster is	 a  column  of
	      the  image).   With  such	 a TIFF	library	and file, you must use
	      -byrow to	get correct output.

	      Before Netpbm 10.11 (October 2002), tifftopnm always did Row  By
	      Row.   Netpbm 10.12 always tried Whole Image first.  -byrow came
	      in with Netpbm 10.13 (January 2003).

       -orientraw
	      A	TIFF stream contains raster data which can be arranged in  the
	      stream  various  ways.   Most  commonly, it is arranged by rows,
	      with the top row first, and the pixels left to right within each
	      row, but many other orientations are possible.

	      The  common  orientation is the same one the Netpbm formats use,
	      so tifftopnm can do its jobs quite  efficiently  when  the  TIFF
	      raster is	oriented that way.

	      But  if the TIFF raster is oriented any other way, it can	take a
	      considerable amount of processing	for tifftopnm to convert it to
	      Netpbm format.

	      -orientraw  says	to produce an output image that	represents the
	      raw raster in the	TIFF stream rather than	 the  image  the  TIFF
	      stream  is  supposed  to represent.  In the output, the top left
	      corner corresponds to the	start of the  TIFF  raster,  the  next
	      pixel  to	 the  right is the next	pixel in the TIFF raster, etc.
	      tifftopnm	can do this easily, but	you don't get the right	 image
	      out.   You can use pamflip to turn the output into the image the
	      TIFF stream represents (but if you do that, you pretty much lose
	      the benefit of -orientraw).

	      With  this  option,  tifftopnm always uses the Row By Row	method
	      (see -byrow).

	      This option was new in Netpbm 10.42 (March 2008).	 Before	 that,
	      tifftopnm	 generally produces arbitrary results with TIFF	images
	      that have	an orientation other than the common one.

       -verbose
	      Print extra messages to Standard Error about the conversion.

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

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 de-
       scription 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 significant bit to least
       significant 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  as-
       sumed  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.
       <ftp://weather.noaa.gov.>  They are apparently  created	by  a  program
       called faxtotiff.

       This note was written on	January	1, 2002.

   Color Separation (CMYK) TIFFs
       Some  TIFF  images  contain color information in	CMYK form, whereas PNM
       images use RGB.	There are  various  formulas  for  converting  between
       these two forms,	and tifftopnm can use either of	two.

       The  TIFF  library  (Version 3.5.4 from libtiff.org) uses Y=(1-K)*(1-B)
       (similar	 for  R	 and  G)  in  its  TIFFRGBAImageGet()  service.	  When
       tifftopnm  works	 in  Whole Image mode, it uses that service, so	that's
       the conversion you get.

       But when	tifftopnm runs in Row By Row mode, it does not use TIFFRGBAIm-
       ageGet(),  and you get what appears to be more useful: Y=1-(B+K).  This
       is the inverse of what pnmtotiffcmyk does.

       See the -byrow option for more information on Whole Image versus	Row By
       Row mode.

       Before Netpbm 10.21 (March 2004), tifftopnm used	the Y=(1-K)*(1-B) for-
       mula always.

SEE ALSO
       pnmtotiff(1), pnmtotiffcmyk(1), pamcomp(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).

DOCUMENT SOURCE
       This manual page	was generated by the Netpbm tool 'makeman'  from  HTML
       source.	The master documentation is at

	      http://netpbm.sourceforge.net/doc/tifftopnm.html

netpbm documentation		02 January 2015	      Tifftopnm	User Manual(0)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | NOTES | SEE ALSO | AUTHOR | DOCUMENT SOURCE

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