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Amiga Format CD 42
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Amiga Format AFCD42 (Issue 126, Aug 1999).iso
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pnmtoljpg.txt
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PNMTOLJPG(1) PNMTOLJPG(1)
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 Huff-
man 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 com-
pressed 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
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PNMTOLJPG(1) PNMTOLJPG(1)
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.
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