jpeg2ktopam



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




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 dou-
       ble 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  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.
       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 gener-
       ates  PBM.   If  the color space is RGB (JAS_IMAGE_CS_RGB), jpeg2ktopam
       generates  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 intensity values in
       the input image have the same meaning as for PGM and  PPM.   One  thing
       that  implies  is  the  ITU-R  Recommendation BT.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 number you can represent in the JPC precision of the JPC compo-
       nent  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 component 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 documentation 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 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

       -verbose
              This option causes jpeg2ktopam to issue  informational  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 com-
       pression 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 (November 2002).



netpbm documentation            27 October 2002     Jpeg2ktopam User Manual(0)

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