Jpeg2ktopam User Manual(0)           Jpeg2ktopam User Manual(0)



Table Of Contents


NAME
       jpeg2ktopam - convert JPEG-2000 code stream to PAM/PNM


SYNOPSIS
       jpeg2ktopam [-verbose] [-debuglevel=number] filename


OPTION USAGE
       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).

       jpeg2ktopam converts the  named  JPEG-2000  code  stream
       file,  or  Standard Input if no file is named, to a PBM,
       PGM, PPM, or PAM file on Standard Output.

       The JPEG-2000 specification specifies two different for-
       mats:  JP2  and JPEG-2000 code stream (JPC).  JP2 repre-
       sents a visual image quite specifically, whereas JPC  is
       a more or less arbitrary array of codes.  JP2 images are
       a subset of JPC images.  jpeg2ktopam  converts  any  JPC
       image.   If  the  color space identified in the image is
       grayscale (JAS_IMAGE_CS_GRAY), jpeg2ktopam  generates  a
       PGM  image,  unless  the image contains only one bit per
       pixel, in which case jpeg2ktopam generates PBM.  If  the
       color  space is RGB (JAS_IMAGE_CS_RGB), jpeg2ktopam gen-
       erates a PPM image.  If  the  input  image  is  anything
       else,  jpeg2ktopam  generates  a PAM image with no tuple
       type identified.

       In the PGM and PPM cases, jpeg2ktopam assumes the inten-
       sity  values in the input image have the same meaning as
       for PGM and PPM.  One thing that implies is the ITU Rec.
       709 color space, which means the assumption is false for
       JP2 input.  JP2 input uses SRGB color encoding.   So  if
       you  use  jpeg2ktopam  to convert a JP2 image to PPM, it
       changes the visual image (slightly) -- the colors in the
       output are not the same as in the input.

       In  the  PAM  image,  the output samples are numerically
       identical to the input samples.  If  the  input  samples
       are  signed,  they  are  represented in two's complement
       form in the  output  (because  PAM  samples  are  always
       unsigned).   The  PAM plane numbers are identical to the
       JPC component numbers.

       A JPC image has a "precision," which is  the  number  of
       bits  used  for  each  code (in Netpbm lingo, "sample").
       Actually, each component has a separate precision.   The
       maxval  of a PGM, PPM, or PAM output is the largest num-
       ber you can represent in the JPC precision  of  the  JPC
       component  with  the greatest precision.  The samples in
       all components are scaled to that maxval.  So if the red
       component has a precision of 4 bits and the green compo-
       nent has a precision of 6 bits, the maxval is 63 and the
       red component codes from the JPC image are multiplied by
       63/15 to generate the output samples.

       jpeg2ktopam interprets the JPC  input  with  the  Jasper
       JPEG-2000  library  .   See documentation of the library
       for details on what jpeg2ktopam handles.  Note that  the
       Jasper  library  contains  facilities  for  writing  PNM
       images, but jpeg2ktopam does not use those.  It uses the
       Netpbm  library  instead.   Note  that the makers of the
       Jasper library write it "JasPer," but Netpbm  documenta-
       tion follows standard American English typography rules,
       which don't allow that kind of capitalization.

       Use pamtojpeg2k 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 fea-
       tures.  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
       -verbose
              This option causes jpeg2ktopam to issue  informa-
              tional messages about the conversion process.


       -debuglevel=number
              This  option  controls  debug  messages  from the
              Jasper library.  jpeg2ktopam passes number as the
              debug level to the Jasper JPC decoder.




EXAMPLES
         jpeg2ktopam myimg.jpc >myimg.ppm



ABOUT JPEG-2000
       See  thepamtojpeg2kmanual(1)  for general information on
       JPEG-2000 compression and the JPEG-2000 formats.




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


History
       jpeg2ktopam was added to Netpbm in Release 10.12 (Novem-
       ber 2002).



netpbm documentation    27 October 20Jpeg2ktopam User Manual(0)
