Jpeg2ktopam User Manual(1) General Commands Manual Jpeg2ktopam User Manual(1)
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 represents 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_IM-
AGE_CS_GRAY), jpeg2ktopam generates a PGM image, unless the image con-
tains 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 encod-
ing. 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 un-
signed). The PAM plane numbers are identical to the JPC component num-
bers.
A JPEG-2000 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 JPEG-2000 precision of the
JPEG-2000 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 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 ]8;;http://www.ece.uvic.ca/~mdadams/jasper/\Jasper JPEG-2000 li-
brary]8;;\ . 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
In addition to the options common to all programs based on libnetpbm
(most notably -quiet, see ]8;;index.html#commonoptions\ Common Options]8;;\ ), jpeg2ktopam recognizes the
following command line 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 the pamtojpeg2k manual(1) for general information on JPEG-2000 com-
pression and the JPEG-2000 formats.
SEE ALSO
pamtojpeg2k(1), jpegtopnm(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.
DOCUMENT SOURCE
This manual page was generated by the Netpbm tool 'makeman' from HTML
source. The master documentation is at
http://netpbm.sourceforge.net/doc/jpeg2ktopam.html
netpbm documentation 08 October 2009 Jpeg2ktopam User Manual(1)
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