Mic’s Blog

Introduction to Libjpeg

The libjpeg package contains libraries that allow compression of image files based on the Joint Photographic Experts Group standard. It is a “lossy” compression algorithm.
如果安装ImageMagick，则需要安装libjpeg来启用jpeg格式支持，
libjpeg用于处理jpeg图片格式，相似的软件还有exiftran，libjpeg经常被php程序所调用，下面是安装方式：

Package Information

• Download (HTTP): http://www.photopost.com/jpegsrc.v6b.tar.gz
• Download (FTP): ftp://ftp.uu.net/graphics/jpeg/jpegsrc.v6b.tar.gz
• Download MD5 sum: dbd5f3b47ed13132f04c685d608a7547

Installation of Libjpeg

Install libjpeg by running the following commands:

./configure --prefix=/usr --enable-static --enable-shared && make

Now, as the root user:

make install

Command Explanations

–enable-static –enable-shared: These switches tell libjpeg to build both shared and static
libraries.

Configuring Libjpeg

Configuration Information
As with most libraries, there is no configuration to do, save that the library directory i.e., /opt/lib or
/usr/local/lib should appear in /etc/ld.so.conf so that ldd can find the shared libraries. After
checking that this is the case, /sbin/ldconfig should be run while logged in as root.

Contents

Installed Programs: cjpeg, djpeg, jpegtran, rdjpgcom, and wrjpgcom
Installed Library: libjpeg.[so,a]
Installed Directories: None

Short Descriptions

1. cjpeg 压制JPEG/JFIF文件 Currently supported input file formats are: PPM (PBMPLUS color format), PGM PBMPLUS gray-scale format), BMP, and Targa.
2. djpeg 还原JPEG/JFIF文件
3. jpegtran is used for lossless transformation of JPEG files.
4. rdjpgcom displays text comments from within a JPEG file.
5. wrjpgcom inserts text comments into a JPEG file.