1Tifftopnm User Manual(0)                              Tifftopnm User Manual(0)
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NAME

6       tifftopnm - convert a TIFF file into a PNM image
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8

SYNOPSIS

10       tifftopnm
11
12       [-alphaout={alpha-filename,-}]  [-headerdump]  [-verbose] [-respectfil‐
13       lorder] [-byrow] [-orientraw] [tiff-filename]
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15
16

DESCRIPTION

18       This program is part of Netpbm(1).
19
20       tifftopnm reads a TIFF file as input and produces a PNM image  as  out‐
21       put.   The  type of the output file depends on the input file - if it's
22       black and white, tifftopnm generates a PBM image; if it's grayscale, it
23       generates a PGM image; otherwise, the output is PPM.  The program tells
24       you which type it is writing.
25
26       If the TIFF file contains  multiple  images  (multiple  "directories"),
27       tifftopnm  generates  a  multi-image  PNM output stream.  Before Netpbm
28       10.27 (March 2005), however, it would just ignore  all  but  the  first
29       input image.
30
31       The tiff-filename argument names the file that contains the Tiff image.
32       If you specify "-" or don't specify this argument, tifftopnm uses Stan‐
33       dard Input.
34
35       In  either  case,  before  Netpbm  10.70 (March 2015), the file must be
36       seekable.  That means no pipe, but any regular file is fine.   In  cur‐
37       rent  Netpbm, the file need not be seekable, but if it isn't, tifftopnm
38       creates a temporary regular file containing the entire  image,  so  you
39       must have resources for that (and it may defeat your reason for using a
40       pipe).
41
42
43
44   TIFF Capability
45       pamtotiff uses the Libtiff.org TIFF library (or whatever equivalent you
46       provide)  to  interpret the TIFF input.  So the set of files it is able
47       to interpret is determined mostly by that library.
48
49       This program cannot read every possible TIFF file -- there  are  myriad
50       variations  of the TIFF format.  However, it does understand monochrome
51       and gray scale, RGB, RGBA (red/green/blue with  transparency  channel),
52       CMYK  (Cyan-Magenta-Yellow-Black  ink color separation), and color pal‐
53       ette TIFF files.  An RGB file can  have  either  single  plane  (inter‐
54       leaved)  color  or multiple plane format.  The program reads 1-8 and 16
55       bit-per-sample input, the latter in  either  bigendian  or  littlendian
56       encoding.   Tiff  directory information may also be either bigendian or
57       littlendian.
58
59       There are many TIFF formats that tifftopnm can read only if  the  image
60       is  small  enough  to fit in memory.  tifftopnm uses the TIFF library's
61       TIFFRGBAImageGet() function to process the TIFF image  if  it  can  get
62       enough memory for TIFFRGBAImageGet() to store the whole image in memory
63       at once (that's what TIFFRGBAImageGet() does).  If not, tifftopnm  uses
64       a  more  primitive  row-by-row  conversion  strategy using the raw data
65       returned by TIFFReadScanLine() and native  intelligence.   That  native
66       intelligence  does not know as many formats as TIFFRGBAImageGet() does.
67       And certain compressed formats simply cannot be read with TIFFReadScan‐
68       Line().
69
70       Before  Netpbm  10.11  (October 2002), tifftopnm never used TIFFRGBAIm‐
71       ageGet(), so it could not interpret many of the formats it  can  inter‐
72       pret today.
73
74       There  is  no fundamental reason that this program could not read other
75       kinds of TIFF files even when they don't fit in  memory  all  at  once.
76       The existing limitations are mainly because no one has asked for more.
77
78
79   Output Image
80       The  PNM  output  has the same maxval as the Tiff input, except that if
81       the Tiff input is colormapped (which implies a maxval of 65535) the PNM
82       output  has  a  maxval of 255.  Though this may result in lost informa‐
83       tion, such input images hardly ever actually have more color resolution
84       than  a  maxval  of  255 provides and people often cannot deal with PNM
85       files that have maxval > 255.   By  contrast,  a  non-colormapped  Tiff
86       image  that doesn't need a maxval > 255 doesn't have a maxval > 255, so
87       when tifftopnm sees a non-colormapped maxval > 255, it takes  it  seri‐
88       ously and produces a matching output maxval.
89
90       Another exception is where the TIFF maxval is greater than 65535, which
91       is the maximum allowed by the Netpbm formats.  In that case,  tifftopnm
92       uses  a  maxval  of 65535, and you lose some information in the conver‐
93       sion.
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95

OPTIONS

97       You may abbreviate any option to its shortest unique prefix.   You  may
98       use  two hyphens instead of one in options.  You may separate an option
99       and its value either by an equals sign or white space.
100
101
102
103       -alphaout=alpha-filename
104              tifftopnm creates a PGM file containing the alpha channel values
105              in the input image.  If the input image doesn't contain a trans‐
106              parency channel,  the  alpha-filename  file  contains  all  zero
107              (transparent)   transparency   values.   If  you  don't  specify
108              -alphaout,
109
110              tifftopnm does not generate a  transparency  file,  and  if  the
111              input  image  has an transparency channel, tifftopnm simply dis‐
112              cards it.
113
114              If you specify - as the filename, tifftopnm  writes  the  trans‐
115              parency output to Standard Output and discards the image.
116
117              See pamcomp(1) for one way to use the transparency output file.
118
119
120       -respectfillorder
121              By  default,  tifftopnm  ignores the "fillorder" tag in the TIFF
122              input, which means it may incorrectly interpret the  image.   To
123              make  it  follow  the  spec, use this option.  For a lengthy but
124              engaging discussion of why tifftopnm works this way and  how  to
125              use  the  -respectfillorder  option,  see  the note on fillorder
126              below.
127
128
129       -byrow This option can make tifftopnm run faster.
130
131              tifftopnm has two ways to do the conversion from  Tiff  to  PNM,
132              using respectively two facilities of the TIFF library:
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134
135
136
137       Whole Image
138              Decode  the  entire image into memory at once, using TIFFRGBAIm‐
139              ageGet(), then convert to PNM and output row by row.
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141
142       Row By Row
143              Read, convert, and output one row at a time using  TIFFReadScan‐
144              line()
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146
147
148              Whole  Image is preferable because the Tiff library does more of
149              the work, which means it understands more  of  the  Tiff  format
150              possibilities now and in the future.  Also, some compressed TIFF
151              formats don't allow you to extract an individual row.
152
153              Row By Row uses far less memory, which means with large  images,
154              it can run in environments where Whole Image cannot and may also
155              run faster.  And because Netpbm code does more of the work, it's
156              possible  that  it  can be more flexible or at least give better
157              diagnostic information if there's something wrong with the TIFF.
158
159              The Netpbm native code may do something correctly that the  TIFF
160              library does incorrectly, or vice versa.
161
162              In Netpbm, we stress function over performance, so by default we
163              try Whole Image first, and if we can't get enough memory for the
164              decoded  image  or TIFFRGBAImageGet() fails, we fall back to Row
165              By Row.  But if you specify the -byrow  option,  tifftopnm  will
166              not attempt Whole Image.  If Row By Row does not work, it simply
167              fails.
168
169              See Color Separation (CMYK) TIFFs ⟨#cmyk⟩  for a description  of
170              one  way  Row  By  Row  makes  a  significant difference in your
171              results.
172
173              Whole Image costs you precision when your TIFF image  uses  more
174              than 8 bits per sample.  TIFFRGBAImageGet() converts the samples
175              to 8 bits.  tifftopnm then scales them back to maxval 65535, but
176              the lower 8 bits of information is gone.
177
178              In  many  versions  of the TIFF library, TIFFRGBAImageGet() does
179              not correctly interpret TIFF files in which the raster  orienta‐
180              tion  is  column-major  (i.e. a row of the raster is a column of
181              the image).  With such a TIFF library and  file,  you  must  use
182              -byrow to get correct output.
183
184              Before  Netpbm 10.11 (October 2002), tifftopnm always did Row By
185              Row.  Netpbm 10.12 always tried Whole Image first.  -byrow  came
186              in with Netpbm 10.13 (January 2003).
187
188
189       -orientraw
190              A  TIFF stream contains raster data which can be arranged in the
191              stream various ways.  Most commonly, it  is  arranged  by  rows,
192              with the top row first, and the pixels left to right within each
193              row, but many other orientations are possible.
194
195              The common orientation is the same one the Netpbm  formats  use,
196              so  tifftopnm  can  do  its jobs quite efficiently when the TIFF
197              raster is oriented that way.
198
199              But if the TIFF raster is oriented any other way, it can take  a
200              considerable amount of processing for tifftopnm to convert it to
201              Netpbm format.
202
203              -orientraw says to produce an output image that  represents  the
204              raw  raster  in  the  TIFF stream rather than the image the TIFF
205              stream is supposed to represent.  In the output,  the  top  left
206              corner  corresponds  to  the  start of the TIFF raster, the next
207              pixel to the right is the next pixel in the  TIFF  raster,  etc.
208              tifftopnm  can do this easily, but you don't get the right image
209              out.  You can use pamflip to turn the output into the image  the
210              TIFF stream represents (but if you do that, you pretty much lose
211              the benefit of -orientraw).
212
213              With this option, tifftopnm always uses the Row  By  Row  method
214              (see -byrow).
215
216              This  option was new in Netpbm 10.42 (March 2008).  Before that,
217              tifftopnm generally produces arbitrary results with TIFF  images
218              that have an orientation other than the common one.
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220
221       -verbose
222              Print extra messages to Standard Error about the conversion.
223
224
225       -headerdump
226              Dump  TIFF  file information to stderr.  This information may be
227              useful in debugging TIFF file conversion problems.
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229
230
231

NOTES

233   Fillorder
234       There is a piece of information in the header of a  TIFF  image  called
235       "fillorder."  The  TIFF  specification  quite  clearly states that this
236       value tells the order in which bits are  arranged  in  a  byte  in  the
237       description  of  the  image's  pixels.  There are two options, assuming
238       that the image has a format where more than one  pixel  can  be  repre‐
239       sented  by  a  single byte: 1) the byte is filled from most significant
240       bit to least significant bit going left to right in the image;  and  2)
241       the opposite.
242
243       However,  there  is  confusion  in  the world as to the meaning of fil‐
244       lorder.  Evidence shows that some people believe it has to do with byte
245       order when a single value is represented by two bytes.
246
247       These  people  cause  TIFF  images to be created that, while they use a
248       MSB-to-LSB fillorder, have a fillorder tag that says they used  LSB-to-
249       MSB.   A  program that properly interprets a TIFF image will not end up
250       with the image that the author intended in this case.
251
252       For a long time, tifftopnm did  not  understand  fillorder  itself  and
253       assumed the fillorder was MSB-to-LSB regardless of the fillorder tag in
254       the TIFF header.  And as far as I know, there is no  legitimate  reason
255       to  use  a fillorder other than MSB-to-LSB.  So users of tifftopnm were
256       happily using those TIFF images that had incorrect fillorder tags.
257
258       So that those users can continue to be happy, tifftopnm today continues
259       to  ignore the fillorder tag unless you tell it not to.  (It does, how‐
260       ever, warn you when the fillorder tag does not say MSB-to-LSB that  the
261       tag is being ignored).
262
263       If  for  some reason you have a TIFF image that actually has LSB-to-MSB
264       fillorder, and its fillorder tag correctly indicates that, you must use
265       the -respectfillorder option on tifftopnm to get proper results.
266
267       Examples  of  incorrect  TIFF  images  are  at  ftp://weather.noaa.gov.
268       ⟨ftp://weather.noaa.gov.⟩  They are apparently  created  by  a  program
269       called faxtotiff.
270
271       This note was written on January 1, 2002.
272
273
274
275   Color Separation (CMYK) TIFFs
276       Some  TIFF  images  contain color information in CMYK form, whereas PNM
277       images use RGB.  There are  various  formulas  for  converting  between
278       these two forms, and tifftopnm can use either of two.
279
280       The  TIFF  library  (Version 3.5.4 from libtiff.org) uses Y=(1-K)*(1-B)
281       (similar  for  R  and  G)  in  its  TIFFRGBAImageGet()  service.   When
282       tifftopnm  works  in  Whole Image mode, it uses that service, so that's
283       the conversion you get.
284
285       But when tifftopnm runs in Row By Row mode, it does not use TIFFRGBAIm‐
286       ageGet(),  and you get what appears to be more useful: Y=1-(B+K).  This
287       is the inverse of what pnmtotiffcmyk does.
288
289       See the -byrow option for more information on Whole Image versus Row By
290       Row mode.
291
292       Before Netpbm 10.21 (March 2004), tifftopnm used the Y=(1-K)*(1-B) for‐
293       mula always.
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295
296

SEE ALSO

298       pnmtotiff(1), pnmtotiffcmyk(1), pamcomp(1), pnm(1)
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300

AUTHOR

302       Derived by Jef Poskanzer from tif2ras.c, which is Copyright (c) 1990 by
303       Sun     Microsystems,     Inc.     Author:    Patrick    J.    Naughton
304       (naughton@wind.sun.com).
305

DOCUMENT SOURCE

307       This manual page was generated by the Netpbm tool 'makeman'  from  HTML
308       source.  The master documentation is at
309
310              http://netpbm.sourceforge.net/doc/tifftopnm.html
311
312netpbm documentation            02 January 2015       Tifftopnm User Manual(0)
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