readme.dist

实现了JPEG-LS的标准算法

SPMG/JPEG-LS IMPLEMENTATION V.2.1
=====================================
These programs are Copyright (c) University of British Columbia. All rights reserved. 
They may be freely redistributed in their entirety provided that this copyright
notice is not removed. THEY MAY NOT BE SOLD FOR PROFIT OR INCORPORATED IN 
COMMERCIAL PROGRAMS WITHOUT THE WRITTEN PERMISSION OF THE COPYRIGHT HOLDER.
Each program is provided as is, without any express or implied warranty,
without even the warranty of fitness for a particular purpose.

=========================================================
THIS SOFTWARE IS BASED ON HP's implementation of jpeg-ls:
=========================================================

LOCO-I/JPEG-LS IMPLEMENTATION V.0.90
-------------------------------------------------------------------------------
(c) COPYRIGHT HEWLETT-PACKARD COMPANY, 1995-1997.
     HEWLETT-PACKARD COMPANY ("HP") DOES NOT WARRANT THE ACCURACY OR 
COMPLETENESS OF THE INFORMATION GIVEN HERE.  ANY USE MADE OF, OR 
RELIANCE ON, SUCH INFORMATION IS ENTIRELY AT USER'S OWN RISK.
     BY DOWNLOADING THE LOCO-I/JPEG-LS COMPRESSORS/DECOMPRESSORS
("THE SOFTWARE") YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS
OF THIS LICENSING AGREEMENT.
     YOU MAY DOWNLOAD AND USE THE SOFTWARE FOR NON-COMMERCIAL PURPOSES
FREE OF CHARGE OR FURTHER OBLIGATION.  YOU MAY NOT, DIRECTLY OR
INDIRECTLY, DISTRIBUTE THE SOFTWARE FOR A FEE, INCORPORATE THIS 
SOFTWARE INTO ANY PRODUCT OFFERED FOR SALE, OR USE THE SOFTWARE 
TO PROVIDE A SERVICE FOR WHICH A FEE IS CHARGED.
     YOU MAY MAKE COPIES OF THE SOFTWARE AND DISTRIBUTE SUCH COPIES TO 
OTHER PERSONS PROVIDED THAT SUCH COPIES ARE ACCOMPANIED BY 
HEWLETT-PACKARD'S COPYRIGHT NOTICE AND THIS AGREEMENT AND THAT
SUCH OTHER PERSONS AGREE TO BE BOUND BY THE TERMS OF THIS AGREEMENT.
     THE SOFTWARE IS NOT OF PRODUCT QUALITY AND MAY HAVE ERRORS OR DEFECTS.
THE JPEG-LS STANDARD IS STILL UNDER DEVELOPMENT. THE SOFTWARE IS NOT A 
FINAL OR FULL IMPLEMENTATION OF THE STANDARD.  HP GIVES NO EXPRESS OR 
IMPLIED WARRANTY OF ANY KIND AND ANY IMPLIED WARRANTIES OF 
MERCHANTABILITY AND FITNESS FOR PURPOSE ARE DISCLAIMED.
     HP SHALL NOT BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL, INCIDENTAL, 
OR CONSEQUENTIAL DAMAGES ARISING OUT OF ANY USE OF THE SOFTWARE. 
-------------------------------------------------------------------------------


This software package contains an implementation of JPEG-LS, the
emerging lossless/near-lossless compression standard for continuous-tone 
images being developed by ISO/IEC JTC1/SC29/WG1 (draft document FCD14495 
as of November 1997). The names of the executables in the software package 
derive from the acronym LOCO, as the core of the new standard is
based on the LOCO-I algorithm (LOw COmplexity LOssless
COmpression for Images) developed at Hewlett-Packard Laboratories
(reference: M. Weinberger, G. Seroussi, G. Sapiro, "LOCO-I: A Low
Complexity, Context-Based, Lossless Image Compression Algorithm,"
Proc. IEEE Data Compression Conference, Snowbird, Utah, March-April 1996).

The term "near-lossless compression" refers to a lossy algorithm
for which each decompressed image sample differs from the corresponding
original image sample by not more than a pre-specified value, the (usually 
small) "loss."  Lossless compression corresponds to loss=0. 
Even though the term "continuous-tone image" refers in principle to any 
image whose components have more than one bit per sample, palletized images 
may require a reordering of the color palette for best compression results 
using LOCO-I on the array of color indices. This functionality is not 
implemented in the present software, although it is supported by the new 
standard, and is easy enough to implement with the tools given. Notice, 
however, that LOCO-I and JPEG-LS were not designed, and might not give 
optimal performance, for images that have been palletized through dithering. 

At various points in the README file, we refer to the FCD14495 draft
standard. An electronic version of the draft is available from the official
JPEG Web site at <http://www.disc.org.uk/public/jpegnew.htm> (a very nice
site worth browsing in any case).


THIS PACKAGE CONTAINS:
----------------------

	README.DIST - this file
        Encoder - contains the encoder's source code. 
        Decoder - contains the dncoder's source code.
        JLSEncoder.exe - the executable of a Win95/NT based 
                         GUI implementation of the jpeg-ls codec
	(The images lena8b.jls and lena24b.jls are provided so that 
          you can immediately "play" with the executable.)

        Two table files which they can be used to test the mapping
        tables:
        "table_r" is for 8bpp PGM's which will reverse the colour.
        "table24_no_red" is also for 8bpp PGM's and converts it to 
         a RGB PPM file but has all its red values 0.  


IMAGE FORMATS:
--------------

	Encoder input (uncompressed) or decoder output (decompressed) 
	images are in either PGM (grayscale) or PPM (3-color) format. 
	These input/output formats are NOT part of the JPEG-LS standard, 
	and they were selected for the sake of simplicity in this 
	implementation.

	The PGM and PPM formats have an ASCII header consisting of 3 lines 
	of the following form:

	    * PGM (single component):

		P5
		cols rows
		maxval

	    * PPM (3 components)

		P6
		cols rows
		maxval
		
	P5 and P6 appear verbatim in the header. The parameters "cols," 
	"rows," and "maxval" are decimal numbers in ASCII representation.
	For PGM, the header is followed by cols*rows samples in binary format,
	where cols and rows are the number of columns and rows, respectively.
	For this implementation, each sample occupies one 8-bit byte if 
	maxval < 256, or two bytes if 256 <= maxval < 65536. In the case of 
	16-bit samples, BIG ENDIAN convention is used (most significant byte 
	first).

	For PPM, the header is followed by cols*rows TRIPLETS of symbols in
	binary format. Each symbol in a triplet represents a color plane 
	value (viewers usually interpret PPM triplets as RGB).

	A multi-component image can be specified to the encoder either as 
	a list of PGM files (each representing a color plane), or as a single 
	PPM-type file.

MULTIPLE-COMPONENT IMAGES:
--------------------------

	Three modes of operation are supported for multi-component images
	(images of the type RGB, CMYK, YUV, etc). This is a subset of the 
	more general scan-based structure supported by JPEG-LS, and is 
	briefly described next:

	   * Plane-by-plane (PbP) compression. The image components are 
	     compressed one after the other, in a completely independent 
	     manner (in JPEG terminology, there is one component per scan). 
	     In this mode, the input to the encoder is one PGM file per 
	     component (i.e., no PPM input is allowed). The same applies to 
	     the output of the decoder.

           * Line-interleaved (LI) compression. One row per image component 
	     is processed at a time, in an interleaved manner (in JPEG
	     terminology, all the components are encoded in the same 
	     scan).  Both multiple PGM file and single file PPM input 
	     (output) are supported by the encoder (decoder). LI mode is 
	     the default mode of this implementation. 

	   * Sample-interleaved (SI) compression. One sample per image 
	     component is processed at a time, in an interleaved manner
	     (again, all the components are encoded in the same scan). 
	     In this mode, the input to the encoder (output from the 
	     decoder) is always a single PPM file.

	Remarks:

        a) Sub-sampled components can be specified to the encoder in
	   PbP and LI modes (e.g., a YUV representation with the U and 
	   V components having a fraction of the number of columns of 
	   the Y component). For sub-sampled images, the input to the 
	   encoder must be given as a sequence of PGM files. JPEG-LS 
	   does not support sub-sampling in SI mode.

	b) Regardless of the input format, the output of the encoder (input 
	   to the decoder), is always a single JPEG-LS compressed bit-stream,
	   consisting of marker segments and compressed image data segments.

	c) The SI mode is recommended only for computer generated compound 
  	   documents. On other image types, this mode is likely to be slower,
	   and compress worse, than the other modes.

	d) For single-component images, the three modes are equivalent.
	   By default, the JPEG-LS header will indicate LI mode in this case.


COMMAND LINES:
--------------

	encoder:
	--------------------------

        locoe [flags] infile1 [infile2,infile3,...] [-ooutfile]

	FILES:
	infile1    : Input file -- must be in PGM or PPM format. If there 
		     are additional input files, then infile1 must be in 
		     PGM format.
	infile2,...: Additional input files for PbP or LI modes. Must be 
		     in PGM format.
	outfile    : Output file in JPEG-LS format. Default = locoe.jls.

        FLAGS, PARAMETERS: 
	(*** NOTE: no spaces allowed between a flag and its argument ***)

	-i<infile> : Alternate input specification, use -i- for stdin.
	-o<outfile>: Output specification, use -o- for stdout 
		     (default=locoe.jls).
	-c<num>    : Mode for multi-component images (program default=1):
		     0:plane-by-plane  
		     1:line-interleaved  
		     2:sample-interleaved.
        -n<error> or
        -e<error>  : Max allowed loss per symbol (default = 0, lossless).

	-h         : Print help.

        OTHER FLAGS AND PARAMETERS:
	The following optional flags allow for overriding of JPEG-LS
	default parameters. Please refer to JPEG-LS specification (FCD14495)
	for details.  *** Use only if you know what you are doing! ***

	-r<num>	   : reset frequency
	-Ta<num>,
	-Tb<num>,
	-Tc<num>   : context modeling thresholds
        -m<table>  : Use mapping table where <table> is a file in the
                     format:
                     1st byte of <table> is the Table ID, 2nd byte
                     of <table> is the Width of each table entry (in bytes),
                     3rd - 6th byte of <table> is the Max Table Index Value
                     specified as an integer (4 bytes), 7th byte and on
                     are the table entries.
        -t<num>    : Use Restart Markers where <num> is the restart interval
                     (ie. number of MCU's between restart markers).


	decoder:
	--------------------------

	locod [flags] [infile] [outfile1 [outfile2,outfile3,...]]

	FILES:
	infile   : Input file in JPEG-LS format. Default = locoe.jls.
	outfile[1,2,...] : Output files. If a single PPM file is generated
		   for a multi-component image (in LI or SI modes), the
		   default name is locod.out. In all other cases, the
		   default names for the of PGM output files are
		   locod1.out, locod2.out, locod3.out, ...

	FLAGS, PARAMETERS:
	-i<infile> : Alternate input specification, use -i- for stdin.
	-o<outfile>: Alternate output specification, use -o- for stdout.
	-P         : Generate single PPM output file for SI or LI modes. This 
		     is the default for SI mode. The default for LI mode (and 
		     only option for PbP mode) is a sequence of PGM files.


EXAMPLES:
---------

	For the examples, assume:
	* red.pgm, green.pgm, and blue.pgm are 3 PGM components of a color
	  image, of the same size.
	* color.ppm is the color PPM image corresponding to red.pgm, 
	  green.pgm, blue.pgm
	* hotely.pgm, hotelu.pgm, hotelv.pgm are 3 components of a color 
	  image sub-sampled in the horizontal direction 2:1:1


	a) locoe red.pgm green.pgm blue.pgm

	   Compresses the three components using the program default color 
	   mode (LI, c=1). Compressed bit-stream is locoe.jls

	   locod

	   Decompresses locoe.jls into 3 PGM files:
	   locod1.out, locod2.out, locod3.out

	   locod locoe.jls a.pgm b.pgm c.pgm

 	   Decompresses locoe.jls into 3 PGM files: a.pgm, b.pgm, c.pgm

 	   locod -P

 	   Decompresses locoe.jls into one PPM file: locod.out


	b) locoe color.ppm
      
 	   Same as (a), using single input


	c) locoe -c0 red.pgm green.pgm blue.pgm

 	   Compresses the three components in PbP mode. Compressed
	   bit-stream is locoe.jls

 	   locod

 	   Decompresses locoe.jls into 3 PGM files: locod1.out, locod2.out, 
 	   locod3.out.

 	   locod -P

	   Since c=0, this command will produce an error.

	d) locoe -c2 color.ppm

           Compresses color.ppm in SI mode. Only one (PPM) input file
	   can be specified in this mode. Compressed bit stream is locoe.jls.

 	   locod

 	   Decompresses locoe.jls into locod.out, a PPM file.
	   Note that -P needs not be specified in this case.

	g) locoe -Ta5 -Tb9 red.pgm

 	   Compresses red.pgm with context thresholds Ta=5, Tb=9, 
	   and Tc=DEFAULT

	h) locoe -r128 green.pgm

 	   Compresses green.pgm with RESET=128.


OTHER CAVEATS, LIMITATIONS, ANNOYANCES, BUGS (?)
=================================================

	* Annoyance: no spaces are allowed between flags and their arguments.
          This will be fixed in a future version.
	* Other bugs, annoyances: guaranteed to exist. Please tell us
	  if you find significant ones. We will be thankful. However, we
	  cannot guarantee that we will maintain the code or that we will
	  satisfy requests for added functionality, recompilation,
	  executables for other operating systems, etc.

Feedback to the SPMG/JPEGLS at UBC:
www.spmg.ece.ubc.ca, or

LOCO-I/JPEG-LS team at HP Labs:
http://www.hpl.hp.com/loco