1Jpeg2ktopam User Manual(0) Jpeg2ktopam User Manual(0)
2
6 jpeg2ktopam - convert JPEG-2000 code stream to PAM/PNM
7
10 jpeg2ktopam [-verbose] [-debuglevel=number] filename
11
14 Minimum unique abbreviation of option is acceptable. You may use dou‐
15 ble hyphens instead of single hyphen to denote options. You may use
16 white space in place of the equals sign to separate an option name from
17 its value.
18
21 This program is part of Netpbm(1).
22 jpeg2ktopam converts the named JPEG-2000 file (JP2 or JPC), or Standard
24 Input if no file is named, to a PBM, PGM, PPM, or PAM file on Standard
25 Output.
26 The JPEG-2000 specification specifies two different formats: JP2 and
28 JPEG-2000 code stream (JPC). JP2 represents a visual image quite
29 specifically, whereas JPC is a more or less arbitrary array of codes.
30 A JP2 image contains a JPC stream and metadata describing how that
31 stream represents a visual image. jpeg2ktopam converts both.
32 If the color space identified in the image is grayscale
34 (JAS_IMAGE_CS_GRAY), jpeg2ktopam generates a PGM image, unless the
35 image contains only one bit per pixel, in which case jpeg2ktopam gener‐
36 ates PBM. If the color space is RGB (JAS_IMAGE_CS_RGB), jpeg2ktopam
37 generates a PPM image. If the input image is anything else,
38 jpeg2ktopam generates a PAM image with no tuple type identified.
39 In the PGM and PPM cases, jpeg2ktopam assumes the intensity values in
41 the input image have the same meaning as for PGM and PPM. One thing
42 that implies is the ITU-R Recommendation BT.709 color space, which
43 means the assumption is false for JP2 input. JP2 input uses SRGB color
44 encoding. So if you use jpeg2ktopam to convert a JP2 image to PPM, it
45 changes the visual image (slightly) -- the colors in the output are not
46 the same as in the input.
47 In the PAM image, the output samples are numerically identical to the
49 input samples. If the input samples are signed, they are represented
50 in two's complement form in the output (because PAM samples are always
51 unsigned). The PAM plane numbers are identical to the JPC component
52 numbers.
53 A JPEG-2000 image has a "precision," which is the number of bits used
55 for each code (in Netpbm lingo, "sample"). Actually, each component
56 has a separate precision. The maxval of a PGM, PPM, or PAM output is
57 the largest number you can represent in the JPEG-2000 precision of the
58 JPEG-2000 component with the greatest precision. The samples in all
59 components are scaled to that maxval. So if the red component has a
60 precision of 4 bits and the green component has a precision of 6 bits,
61 the maxval is 63 and the red component codes from the JPEG-2000 image
62 are multiplied by 63/15 to generate the output samples.
63 jpeg2ktopam interprets the JPEG-2000 input with the Jasper JPEG-2000
65 library ⟨http://www.ece.uvic.ca/~mdadams/jasper/⟩ . See documentation
66 of the library for details on what jpeg2ktopam handles. Note that the
67 Jasper library contains facilities for writing PNM images, but
68 jpeg2ktopam does not use those. It uses the Netpbm library instead.
69 Note that the makers of the Jasper library write it "JasPer," but
70 Netpbm documentation follows standard American English typography
71 rules, which don't allow that kind of capitalization.
72 Use pamtojpeg2k to convert in the other direction.
74 The program jasper, which is packaged with the Jasper JPEG-2000
76 library, also converts between JPEG-2000 and PNM formats. Because it's
77 packaged with the library, it may exploit it better, especially
78 recently added features. However, since it does not use the Netpbm
79 library to read and write the Netpbm formats, it doesn't do as good a
80 job on that side.
81
84 -verbose
85 This option causes jpeg2ktopam to issue informational messages
86 about the conversion process.
87 -debuglevel=number
90 This option controls debug messages from the Jasper library.
91 jpeg2ktopam passes number as the debug level to the Jasper
92 JPEG-2000 decoder.
93
98 jpeg2ktopam myimg.jpc >myimg.ppm
99
103 See thepamtojpeg2kmanual(1) for general information on JPEG-2000 com‐
104 pression and the JPEG-2000 formats.
105
109 jpctopam(1), pnmtopeg(1), ppm(1), pgm(1), pbm(1), pam(1),
110
113 jpeg2ktopam was added to Netpbm in Release 10.12 (November 2002).
114 Before Netpbm 10.49 (December 2009), jpeg2ktopam could not convert a
116 JP2 file -- only JPC.
117netpbm documentation 08 October 2009 Jpeg2ktopam User Manual(0)