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Pamtojpeg2k User Manual(0)					       Pamtojpeg2k User Manual(0)

NAME
       pamtojpeg2k - convert PAM/PNM image to a JPEG-2000 code stream

SYNOPSIS
       pamtojpeg2k  [-imgareatlx=column] [-imgareatly=row] [-tilegrdtlx=column] [-tilegrdtly=row]
       [-tilewidth=columns]  [-tileheight=rows]  [-prcwidth=columns]  [-prcheight=rows]   [-cblk-
       width=columns]	 [-cblkheight=rows]    [-mode={integer|int|real}]    [-compression=ratio]
       [-ilyrrates=ratestring]	  [-numrlvls=number]	[-progression={lrcp|rlcp|rpcl|pcrl|cprl}]
       [-numgbits=number] [-nomct] [-sop] [-eph] [-lazy] [-termall] [-segsym] [-vcausal] [-pterm]
       [-resetprob] [-verbose] [-debuglevel=number] filename

       Minimum unique abbreviation of option is acceptable.  You may use double  hyphens  instead
       of  single  hyphen to denote options.  You may use white space in place of the equals sign
       to separate an option name from its value.

DESCRIPTION
       This program is part of Netpbm(1)

       pamtojpeg2k converts the named PBM, PGM, PPM, or PAM file, or Standard Input if no file is
       named, to a JPEG-2000 code stream (JPC) file on Standard Output.

       The JPEG-2000 specification specifies two different formats: JP2 and JPEG-2000 code stream
       (JPC).  JP2 represents a visual image quite specifically, whereas JPC is a  more  or  less
       arbitrary  array of codes.  pamtojpeg2k can't produce a JP2, but the JPC image that pamto-
       jpeg2k produces is very similar to a JP2 if the input is a  PBM,  PGM,  or  PPM	image  or
       equivalent  PAM	image.	One difference is that the RGB intensity values in a JP2 are SRGB
       values, while pamtojpeg2k produces ITU-R Recommendation BT.709  values.	 Those	are  very
       similar,  but  not identical.  Another difference is that a JP2 can contain extra informa-
       tion about an image that JPC cannot.

       When the input is a PAM image other than a PBM, PGM, or PPM  equivalent,  the  JPC  raster
       produced contains whatever the PAM raster does.	It can have any number of planes with any
       meanings; the planes are in the same order in the JPC output as in the PAM input.

       A JPC image has a "precision," which is the number of bits used for each code  (in  Netpbm
       lingo,  "sample").  Actually, it has a separate precision for each component.  pamtojpeg2k
       uses for the precision of every component the least number of bits that can represent  the
       maxval  of  the	input image.  A JPC image does not have an independent concept of maxval;
       the maxval of a JPC sample is the maximum value that the number of bits specified  by  the
       precision  can  represent  in pure binary code.	E.g. if the precision is 4, the maxval is
       15.  pamtojpeg2k does of course scale the sample values from the input maxval to the  out-
       put  maxval.  Example: The input maxval is 99.  This means JPC precision is 7 bits and the
       JPC maxval is 127.  A sample value of 33 in the input becomes a sample value of 43 in  the
       output.

       pamtojpeg2k    generates    the	 JPC   output	with   the   Jasper   JPEG-2000   library
       <http://www.ece.uvic.ca/~mdadams/jasper/> .  See documentation of the library for  details
       on  what pamtojpeg2k produces.  Note that the Jasper library contains facilities for read-
       ing PNM images, but pamtojpeg2k does not use those.  It uses the Netpbm	library  instead.
       Note  that  the	makers	of the Jasper library write it "JasPer," but Netpbm documentation
       follows standard American English typography rules, which don't allow that kind	of  capi-
       talization.

       Use jpeg2ktopam to convert in the other direction.

       The  program  jasper,  which  is packaged with the Jasper JPEG-2000 library, also converts
       between JPEG-2000 and PNM formats.  Because it's packaged with the library, it may exploit
       it  better, especially recently added features.	However, since it does not use the Netpbm
       library to read and write the Netpbm formats, it doesn't do as good a job on that side.

OPTIONS
       Most of the options are identical in name and function to options that the Jasper  library
       JPC	 encoder       subroutine	takes.	      See	Jasper	    documentation
       <http://www.ece.uvic.ca/~mdadams/jasper/>  for details.	Here, we  document  only  options
       that are not direct analogs of Jasper options.

       -compression=ratio
	      ratio is a floating point number that specifies the compression ratio.  pamtojpeg2k
	      will adjust quality as necessary to ensure that you  get	this  compression  ratio.
	      E.g.  4  means  the  output will be about one fourth the size in bytes of the input
	      file.

	      The ratio concerns just the raster part of the image, with  the  denominator  being
	      what  the  raster would take if it were encoded the most naive way possible (e.g. 3
	      bytes per pixel in 8-bit-per-sample RGB).  It does, however, include metadata  that
	      is  part of the compressed raster.  Because of that, it may not be possible to give
	      you your requested compression ratio at any  quality.   If  it  isn't,  pamtojpeg2k
	      fails with a message saying so.

	      If you don't specify this option, pamtojpeg2k gives you the best compression it can
	      without losing any quality.  Because of the metadata issue  described  above,  this
	      may mean, for a small image, the image actually expands.

	      Note  that though the Jasper library takes a compression factor, this option speci-
	      fies a compression ratio.  The compression factor is the multiplicative inverse  of
	      (1 divided by) the compression ratio.

	      Before  Netpbm 10.61 (December 2012), the default was a compression ratio of 1, and
	      if pamtojpeg2k could not make the output that small, it just made it as small as it
	      could, with zero quality.  You know this is happening when you see the warning mes-
	      sage, 'empty layer generated.'

       -verbose
	      This option causes pamtojpeg2k to issue informational messages about the conversion
	      process.

       -debuglevel=number
	      This  option  controls  debug messages from the Jasper library.  pamtojpeg2k passes
	      number as the debug level to the Jasper JPC encoder.

EXAMPLES
       This example compresses losslessly.

	 pamtojpeg2k myimg.ppm >myimg.jpc

       jpeg2ktopam will recreate myimg.ppm exactly.

       This example compresses the file to one tenth its original size, throwing away information
       as necessary.

	 pamtojpeg2k -compression=10 myimg.pgm >myimg.jpc

ABOUT JPEG-2000
       JPEG-2000  is  a  format  that compresses a visual image (or a similar set of data) into a
       minimal number of bytes for storage or transmission.  In that,  its  goal  is  similar  to
       JPEG.  It has two main differences from JPEG.

       One  difference	is that it does a much better job on most images of throwing out informa-
       tion in order to achieve a smaller output.  That means when you reconstruct the image from
       the  resulting  compressed  file,  it  looks  a	lot  closer to the image you started with
       JPEG-2000 than with JPEG, for the same compressed file size.  Or, looked at  another  way,
       with JPEG-2000 you get a much smaller file than with JPEG for the same image quality.

       The second difference is that with JPEG-2000, you decide how much compression you want and
       the compressor adjusts the quality to meet your requirement, whereas with JPEG, you decide
       how  much  quality you want and the compressor adjusts the size of the output to meet your
       requirement.  I.e. with JPEG-2000, the quality of the result depends on the  compressibil-
       ity  of the input, but with JPEG, the size of the result depends on the compressibility of
       the input.

       With JPEG-2000, you can specify lossless compression, thus making it compete with GIF  and
       PNG.   With standard JPEG, you always lose something.  (There are rumored to be variations
       of JPEG around that are lossless, though).

       JPEG is much older than JPEG-2000 and far more popular.	JPEG is one  of  the  half  dozen
       most  popular  graphics	formats  and  virtually  all  graphics	facilities understand it.
       JPEG-2000 is virtually unknown.

       There is no compatibility between JPEG and JPEG-2000.  Programs	that  read  JPEG  do  not
       automatically read JPEG-2000 and vice versa.

SEE ALSO
       jpeg2ktopam(1) , pnmtopeg(1) , ppm(1) , pgm(1) , pbm(1) , pam(1) ,

History
       pamtojpeg2k was added to Netpbm in Release 10.12 (November 2002).

netpbm documentation			 27 October 2002	       Pamtojpeg2k User Manual(0)
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