The Independent JPEG Group's JPEG software
==========================================
README for release 6b of 27-Mar-1998
====================================
This distribution contains the sixth public release of the Independent JPEG
Group's free JPEG software. You are welcome to redistribute this software and
to use it for any purpose, subject to the conditions under LEGAL ISSUES, below.
Serious users of this software (particularly those incorporating it into
larger programs) should contact IJG at jpeg-info@uunet.uu.net to be added to
our electronic mailing list. Mailing list members are notified of updates
and have a chance to participate in technical discussions, etc.
This software is the work of Tom Lane, Philip Gladstone, Jim Boucher,
Lee Crocker, Julian Minguillon, Luis Ortiz, George Phillips, Davide Rossi,
Guido Vollbeding, Ge' Weijers, and other members of the Independent JPEG
Group.
IJG is not affiliated with the official ISO JPEG standards committee.
DOCUMENTATION ROADMAP
=====================
This file contains the following sections:
OVERVIEW General description of JPEG and the IJG software.
LEGAL ISSUES Copyright, lack of warranty, terms of distribution.
REFERENCES Where to learn more about JPEG.
ARCHIVE LOCATIONS Where to find newer versions of this software.
RELATED SOFTWARE Other stuff you should get.
FILE FORMAT WARS Software *not* to get.
TO DO Plans for future IJG releases.
Other documentation files in the distribution are:
User documentation:
install.doc How to configure and install the IJG software.
usage.doc Usage instructions for cjpeg, djpeg, jpegtran,
rdjpgcom, and wrjpgcom.
*.1 Unix-style man pages for programs (same info as usage.doc).
wizard.doc Advanced usage instructions for JPEG wizards only.
change.log Version-to-version change highlights.
Programmer and internal documentation:
libjpeg.doc How to use the JPEG library in your own programs.
example.c Sample code for calling the JPEG library.
structure.doc Overview of the JPEG library's internal structure.
filelist.doc Road map of IJG files.
coderules.doc Coding style rules --- please read if you contribute code.
Please read at least the files install.doc and usage.doc. Useful 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 compression and
decompression. JPEG (pronounced "jay-peg") is a standardized compression
method for full-color and gray-scale images. JPEG is intended for compressing
"real-world" scenes; line drawings, cartoons and other non-realistic images
are not its strong suit. JPEG is lossy, meaning that the output image is not
exactly identical to the input image. Hence you must not use JPEG if you
have to have identical output bits. However, on typical photographic images,
very good compression levels can be obtained with no visible change, and
remarkably high compression levels are possible if you can tolerate a
low-quality image. For more details, see the references, or just experiment
with various compression settings.
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.
For legal reasons, we are not distributing code for the arithmetic-coding
variants of JPEG; see LEGAL ISSUES. 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:
The authors make NO WARRANTY or representation, either express or implied,
with respect to this software, its quality, accuracy, merchantability, or
fitness for a particular purpose. This software is provided "AS IS", and you,
its user, assume the entire risk as to its quality and accuracy.
This software is copyright (C) 1991-1998, Thomas G. Lane.
All Rights Reserved except as specified below.
Permission is hereby granted to use, copy, modify, and distribute this
software (or portions thereof) for any purpose, without fee, subject to these
conditions:
(1) If any part of the source code for this software is distributed, then this
README file must be included, with this copyright and no-warranty notice
unaltered; and any additions, deletions, or changes to the original files
must be clearly indicated in accompanying documentation.
(2) If only executable code is distributed, then the accompanying
documentation must state that "this software is based in part on the work of
the Independent JPEG Group".
(3) Permission for use of this software is granted only if the user accepts
full responsibility for any undesirable consequences; the authors accept
NO LIABILITY for damages of any kind.
These conditions apply to any software derived from or based on the IJG code,
not just to the unmodified library. If you use our work, you ought to
acknowledge us.
Permission is NOT granted for the use of any IJG author's name or company name
in advertising or publicity relating to this software or products derived from
it. This software may be referred to only as "the Independent JPEG Group's
software".
We specifically permit and encourage the use of this software as the basis of
commercial products, provided that all warranty or liability claims are
assumed by the product vendor.
ansi2knr.c is included in this distribution by permission of
CxImage的VC源码
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**标题与描述解析**
标题"CxImage的VC源码"指的是一个专为Visual C++(VC)开发的图像处理库的源代码,该库名为CxImage。它允许开发者在C++环境中处理各种图像格式,包括但不限于JPG、EJPG和TAG等。这通常涉及到图像的读取、显示、编辑和保存等一系列功能。
描述中提到"CxImage是一个用于处理各种图像格式的VC类",这暗示了CxImage是一个基于面向对象编程的库,它通过类和对象的方式来封装图像处理的复杂逻辑,提供了一套接口供开发者调用。它支持多种常见的图像格式,意味着开发者无需了解每种格式的底层细节,就可以实现对不同格式图片的高效操作。
**知识点详解**
1. **面向对象编程**:CxImage是基于C++的面向对象设计,这意味着它由一系列类组成,每个类代表图像处理中的特定概念或功能。例如,可能有一个类专门负责图像的加载,另一个类则专注于图像的滤波效果。
2. **图像格式处理**:CxImage库的核心功能是支持多种图像格式的读取和写入,如JPEG(JPG)、Enhanced JPEG(EJPG)和Tagged Image File Format(TIFF,通常写作TAG)。这些格式各有特点,例如JPEG适用于高质量的有损压缩,EJPG可能是一种增强型的JPEG格式,而TIFF则是无损格式,适合于专业图像编辑。
3. **图像操作接口**:这个库提供了丰富的API接口,使得开发者可以进行图像的基本操作,如调整尺寸、旋转、裁剪、颜色转换,以及应用滤镜效果等。例如,可以使用API来调整图像的亮度、对比度,或者应用模糊、锐化等效果。
4. **内存管理**:在处理图像时,CxImage可能涉及内存管理,包括加载图像到内存、在内存中操作图像,以及将结果保存回磁盘。这需要有效地管理和优化内存使用,避免内存泄漏和性能瓶颈。
5. **性能优化**:由于图像处理往往涉及大量计算,所以库的设计会考虑性能优化,如使用缓存策略、多线程处理、硬件加速等技术。
6. **跨平台性**:虽然题目主要提及VC环境,但许多C++库都致力于跨平台兼容,这意味着CxImage可能也能在其他操作系统上运行,如Linux或macOS,前提是它们支持必要的图形库。
7. **集成到项目**:将CxImage库整合到VC项目中,可能涉及到设置头文件路径、链接库文件、处理编译和链接选项,以及理解库的API文档以正确使用其功能。
8. **错误处理**:在实际应用中,开发者还需要关注错误处理,如读取文件失败、格式不支持、内存不足等情况,确保程序的健壮性。
9. **版本更新与社区支持**:作为一个开源库,CxImage可能会有持续的版本更新,修复问题,增加新功能,并且有社区的支持,开发者可以通过社区获取帮助,交流经验。
CxImage是一个强大的图像处理工具,它简化了开发者在C++环境中处理图像的工作,提供了丰富的功能和良好的可扩展性。通过理解和熟练使用它的API,开发者可以构建出各种图像处理应用,满足不同的需求。
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