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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 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 file (JP2 or JPC), 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  repre-
       sents  a  visual image quite specifically, whereas JPC is a more or less arbitrary array of codes.  A JP2 image
       contains a JPC stream and metadata describing how that stream represents a visual image.  jpeg2ktopam  converts
       both.

       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 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 JPEG-2000 image has a "precision," which is the number of bits used for each code  (in  Netpbm  lingo,  "sam-
       ple").   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 JPEG-2000 precision of the JPEG-2000 component with the greatest preci-
       sion.   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
       JPEG-2000 image are multiplied by 63/15 to generate the output samples.

       jpeg2ktopam  interprets  the  JPEG-2000  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  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 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 JPEG-2000 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 (November 2002).

       Before Netpbm 10.49 (December 2009), jpeg2ktopam could not convert a JP2 file -- only JPC.



netpbm documentation            08 October 2009     Jpeg2ktopam User Manual(0)