pnmtotiff


SYNOPSIS
       pnmtotiff  [-none|-packbits|-lzw|-g3|-g4]  [-2d] [-fill] [-predictor n]
       [-msb2lsb|-lsb2msb] [-rowsperstrip n] [-minisblack|-miniswhite] [-true-
       color] [-color] [-indexbits 1|2|4|8] [pnmfile]


       Minimum unambiguous abbreviations of options are acceptable.


DESCRIPTION
       Reads a PNM image as input.  Produces a TIFF file as output.

       The  output  goes  to  Standard  Output, which must be a seekable file.
       That means no pipes, but any regular file should work.



OPTIONS
       By default, pnmtotiff creates a TIFF file with no compression.  This is
       your best bet most of the time.  If you want to try another compression
       scheme or tweak some of the other even  more  obscure  output  options,
       there are a number of flags to play with.

       Actually,  the  best  default would be to use LZW compression, which is
       what pnmtotiff used to do by default.  However,  the  Tiff  library  no
       longer  does  LZW  compression  due to concerns with violating Unisys's
       patent on LZW compression.

       The -none, -packbits, -lzw, -g3, -g4, -flate,  and  -adobeflat  options
       are used to override the default and set the compression scheme used in
       creating the output file.  The CCITT Group 3 and  Group  4  compression
       algorithms  can  only  be  used with bilevel data.  -lzw doesn't really
       work because the Tiff library doesn't do LZW compression.  It used  to,
       but  its developers removed the function out of concern about violating
       Unisys's patent.  This option remains in case you use  a  Tiff  library
       that  cooperates,  now or in the future.  The -2d and -fill options are
       meaningful only with Group 3 compression:  -2d  requests  2-dimensional
       encoding,  while  -fill  requests  that  each encoded scanline be zero-
       filled to a byte boundry.  The -predictor  option  is  only  meaningful
       with  LZW  compression:  a predictor value of 2 causes each scanline of
       the output image  to  undergo  horizontal  differencing  before  it  is
       encoded;  a  value of 1 forces each scanline to be encoded without dif-
       ferencing.

       By default, pnmtotiff creates a TIFF file with msb-to-lsb  fill  order.
       The  -msb2lsb and -lsb2msb options are used to override the default and
       set the fill order used in creating the file.

       The fill order is the order in which pixels are packed into a  byte  in
       the  Tiff  raster, in the case that there are multiple pixels per byte.
       msb-to-lsb means that the leftmost columns go into the most significant
       bits  of  the  byte  in the Tiff image.  However, there is considerable
       confusion about the meaning of  fill  order.   Some  believe  it  means
       The -rowsperstrip option can be used to set the number of  rows  (scan-
       lines)  in each strip of data in the output file.  By default, the out-
       put file has the number of rows per strip set  to  a  value  that  will
       ensure each strip is no more than 8 kilobytes long.

       The -minisblack and -miniswhite option force the output image to have a
       "minimum is black" or "minimum is white" photometric, respectively.  If
       you  don't  specify either, pnmtotiff uses minimum is black except when
       using Group 3 or Group 4 compression, in which case  pnmtotiff  follows
       CCITT  fax standards and uses "minimum is white."  This usually results
       in better compression and is generally preferred for bilevel coding.

       Before February 2001, pnmtotiff always produced "minimum is black," due
       to  a  bug.  In either case, pnmtotiff sets the photometric interpreta-
       tion tag in the TIFF output according to which photometric is  actually
       used.

       -truecolor  tells pnmtotiff to produce the 24-bit RGB form of TIFF out-
       put if it is producing a color TIFF image.  Without this option, pnmto-
       tiff  produces  a  colormapped (paletted) 8-bit TIFF image unless there
       are more than 256 colors (and in the latter case, issues a warning).

       The -truecolor option can prevent  pnmtotiff  from  making  two  passes
       through the input file, thus improving speed and memory usage.  See the
       section MULTIPLE PASSES.

       If pnmtotiff produces a  grayscale  TIFF  image,  this  option  has  no
       effect.

       -color  tells  pnmtotiff  to  produce a color, as opposed to grayscale,
       TIFF image if the input is PPM, even if  it  contains  only  shades  of
       gray.   Without  this option, pnmtotiff produces a grayscale TIFF image
       if the input is PPM and contains only shades of gray, and at  most  256
       shades.   Otherwise,  it produces a color TIFF output.  For PBM and PGM
       input, pnmtotiff always produces grayscale TIFF output and this  option
       has no effect.

       The  -color option can prevent pnmtotiff from making two passes through
       the input file, thus improving speed and memory usage.  See the section
       MULTIPLE PASSES.

       The  -indexbits  option is meaningful only for a colormapped (paletted)
       image. In this kind of image, the  raster  contains  values  which  are
       indexes  into  a table of colors, with the indexes normally taking less
       space that the color description in the table. pnmtotiff  can  generate
       indexes  of 1, 2, 4, or 8 bits. By default, it will use 8, because many
       programs that interpret TIFF images can't handle any other width.


NOTES
       There are myriad variations of the TIFF format, and this program gener-
       ates  only  a  few of them.  pnmtotiff creates a grayscale TIFF file if
       its input is a PBM (monochrome) or  PGM  (grayscale)  file.   pnmtotiff
       also  creates a grayscale file if it input is PPM (color), but there is


   Multiple Passes
       pnmtotiff  reads  the  input image once if it can, and otherwise twice.
       It needs that second pass to analyze the colors in the image and gener-
       ate a color map (pallette) and determine if the image is grayscale.  So
       the second pass only happens when the input is PPM.  And you can  avoid
       it then by specifying both the -truecolor and -color options.

       If  the input image is small enough to fit in your system's file cache,
       the second pass is very fast.  If not, it requires  reading  from  disk
       twice, which can be slow.

       When the input is from a file that cannot be rewound and reread, pnmto-
       tiff reads the entire input image into a temporary file which can,  and
       works from that.  Even if it only needs one pass.


SEE ALSO
       tifftopnm(1), pnmtotiffcmyk(1), pnmdepth(1), pnm(5)


AUTHOR
       Derived  by  Jef Poskanzer from ras2tiff.c, which is Copyright (c) 1990
       by   Sun   Microsystems,   Inc.    Author:    Patrick    J.    Naughton
       (naughton@wind.sun.com).



                                24 January 2001                   pnmtotiff(1)
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