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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 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
       ⟨http://www.ece.uvic.ca/~mdadams/jasper/⟩ .  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	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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