pnmtoljpg.1

很好的JPEG图象解码器,基于VC环境开发。

.TH PNMTOLJPG 1 "14 June 1994"
.SH NAME
pnmtoljpg \- compress a Portable Pixmap or Portable Graymap image \
file to a lossless JPEG file
.SH SYNOPSIS
.B pnmtoljpg
[
.B \-d
]
[
.B \-h
]
[
.B \-p#
]
[
.B \-r#
]
[
.B \-s{1..7}
]
[
.B \-v
]
[
.I filename ...
]
.LP
.SH DESCRIPTION
.LP
.B 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.
.SH OPTIONS
.TP
.B \-d
Use default Huffman table. If this flag is not specified, pnmtoljpg
will generate an optimal Huffman table.
.TP
.B \-h "--help"
Display a help screen and quit.
.TP
.B \-p#
The #, an integer less than sample precision bits, is the point
tranform parameter. 
.TP
.B \-r#
Restart at every # row(s).
.TP
.B \-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.
.TP
.B \-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.  
.SH EXAMPLES
.LP
This example compresses a PPM file foo.ppm with optimal Huffman  
table and the default PSV set. The output is foo.ljpg.
.IP
.B pnmtoljpg
.I foo.ppm foo.ljpg
.LP
Next example compresses a PGM file foo.pgm with default Huffman  
table and PSV 4. The output is saved as foo.ljpg.
.IP
.B pnmtoljpg
.I -d -s4
.B <
.I foo.ppm
.B >
.I foo.ljpg
.LP
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.
.IP
.B pnmtoljpg
.I -v -s246
.I foo.ppm
.B >
.I foo.ljpg
.SH SEE ALSO
.BR ljpgtopnm(1),
.BR ppm (5),
.BR pgm (5)
.br
Wallace, Gregory K.  "The JPEG Still Picture Compression Standard",
Communications of the ACM, April 1991 (vol. 34, no. 4), pp. 30-44.
.SH AUTHOR
Kongji Huang and Brian Smith
.SH BUGS
Arithmetic coding and multiple scans are not supported.
.PP
Comments in PPM/PGM files are not stored in the LJPG files.