PNMTOLJPG
Section: User Commands (1)
Updated: 14 June 1994
Index
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NAME
pnmtoljpg - compress a Portable Pixmap or Portable Graymap image file to a lossless JPEG file
SYNOPSIS
pnmtoljpg
[
-d
]
[
-h
]
[
-p#
]
[
-r#
]
[
-s{1..7}
]
[
-v
]
[
filename ...
]
DESCRIPTION
pnmtoljpg
compresses a PPM (Portable Pixmap) or a PGM (Portable Graymap) image,
and produces a lossless JPEG (LJPG) file. If no files are specified,
the standard input is compressed to the standard output.
OPTIONS
- -d
-
Use default Huffman table. If this flag is not specified, pnmtoljpg
will generate an optimal Huffman table.
- -h --help
-
Display a help screen and quit.
- -p#
-
The #, an integer less than sample precision bits, is the point
tranform parameter.
- -r#
-
Restart at every # row(s).
- -s{1..7}
-
Supply a prediction selection value (PSV) set, {1..7}. The pnmtoljpg
tries all PSVs in the set and select the best one. A PSV is an integer
between 1 and 7 inclusively. If a "-s" flag is not provided,
pnmtoljpg will try all seven PSVs.
- -v verbose
-
Display data about image format, image size, sample precision, total
bytes category symbols, total bytes of additional symbols, original
and compressed file size, and compress ratio.
EXAMPLES
This example compresses a PPM file foo.ppm with optimal Huffman
table and the default PSV set. The output is foo.ljpg.
-
pnmtoljpg
foo.ppm foo.ljpg
Next example compresses a PGM file foo.pgm with default Huffman
table and PSV 4. The output is saved as foo.ljpg.
-
pnmtoljpg
-d -s4
<
foo.ppm
>
foo.ljpg
The last example compresses a PPM file foo.ppm with optimal Huffman
table and a PSV set {246}. The verbose flag is on, and the output is
saved as foo.ljpg.
-
pnmtoljpg
-v -s246
foo.ppm
>
foo.ljpg
SEE ALSO
ljpgtopnm(1),
ppm(5),
pgm(5)
Wallace, Gregory K. "The JPEG Still Picture Compression Standard",
Communications of the ACM, April 1991 (vol. 34, no. 4), pp. 30-44.
AUTHOR
Kongji Huang and Brian Smith
BUGS
Arithmetic coding and multiple scans are not supported.
Comments in PPM/PGM files are not stored in the LJPG files.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- EXAMPLES
-
- SEE ALSO
-
- AUTHOR
-
- BUGS
-
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