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Polycom CMA Desktop Help Book
30
rdjpgcom, and wrjpgcom.
*.1 Unix-style man pages for programs (same info as usage.txt).
wizard.txt Advanced usage instructions for JPEG wizards only.
change.log Version-to-version change highlights.
Programmer and internal documentation:
libjpeg.txt How to use the JPEG library in your own programs.
example.c Sample code for calling the JPEG library.
structure.txt Overview of the JPEG library's internal structure.
filelist.txt Road map of IJG files.
coderules.txt Coding style rules --- please read if you contribute code.
Please read at least the files install.txt and usage.txt. Some information can also be found in the JPEG FAQ
(Frequently Asked Questions) article. See ARCHIVE LOCATIONS below to find out where to obtain the FAQ article.
If you want to understand how the JPEG code works, we suggest reading one or more of the REFERENCES, then
looking at the documentation files (in roughly the order listed) before diving into the code.
OVERVIEW
This package contains C software to implement JPEG image encoding, decoding, and transcoding. JPEG
(pronounced "jay-peg") is a standardized compression method for full-color and gray-scale images.
This software implements JPEG baseline, extended-sequential, and progressive compression processes. Provision
is made for supporting all variants of these processes, although some uncommon parameter settings aren't
implemented yet. We have made no provision for supporting the hierarchical or lossless processes defined in the
standard.
We provide a set of library routines for reading and writing JPEG image files, plus two sample applications "cjpeg"
and "djpeg", which use the library to perform conversion between JPEG and some other popular image file formats.
The library is intended to be reused in other applications.
In order to support file conversion and viewing software, we have included considerable functionality beyond the bare
JPEG coding/decoding capability; for example, the color quantization modules are not strictly part of JPEG decoding,
but they are essential for output to colormapped file formats or colormapped displays. These extra functions can be
compiled out of the library if not required for a particular application.
We have also included "jpegtran", a utility for lossless transcoding between different JPEG processes, and
"rdjpgcom" and "wrjpgcom", two simple applications for inserting and extracting textual comments in JFIF files.
The emphasis in designing this software has been on achieving portability and flexibility, while also making it fast
enough to be useful. In particular, the software is not intended to be read as a tutorial on JPEG. (See the
REFERENCES section for introductory material.) Rather, it is intended to be reliable, portable, industrial-strength
code. We do not claim to have achieved that goal in every aspect of the software, but we strive for it.
We welcome the use of this software as a component of commercial products. No royalty is required, but we do ask
for an acknowledgement in product documentation, as described under LEGAL ISSUES.
LEGAL ISSUES
In plain English:
1. We don't promise that this software works. (But if you find any bugs, please let us know!)
2. You can use this software for whatever you want. You don't have to pay us.
3. You may not pretend that you wrote this software. If you use it in a program, you must acknowledge
somewhere in your documentation that you've used the IJG code.
In legalese: