Jpeg2ktopam

   Updated: 27 October 2002
   Table Of Contents

NAME

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

SYNOPSIS

   jpeg2ktopam [-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.

   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 Stan-
dard Output.

   The	JPEG-2000  specification specifies two different formats:
JP2 and
   JPEG-2000  code  stream  (JPC).  JP2	 represents  a visual im-
age 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_IM-
AGE_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 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 number 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 com-
ponent 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 sam-
ples.

   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 in-
stead. 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	 the   pamtojpeg2k  manual  for	 general  information  on
JPEG-2000 compression
   and the JPEG-2000 formats.

SEE ALSO

   jpctopam, pnmtopeg, ppm, pgm, pbm, pam,

History

   jpeg2ktopam was added to Netpbm  in	Release	 10.12	(November
2002).
     _________________________________________________________________



Table Of Contents

     * SYNOPSIS
     * DESCRIPTION
     * OPTIONS
     * EXAMPLES
     * SEE ALSO

UNIX/Linux commands referenced on this page:

1. convert
2. file
3. more
4. less
5. which
6. as
7. red
8. write
9. pamtojpeg2k