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按照官方的说法：Cairo is a vector graphics library with cross-device output support. 翻译过来

Cairo - Multi-platform 2D graphics library
http://cairographics.org

What is cairo
=============
Cairo is a 2D graphics library with support for multiple output
devices. Currently supported output targets include the X Window
System, win32, and image buffers. Experimental backends include OpenGL
(through glitz), Quartz, XCB, PostScript and PDF file output.

Cairo is designed to produce consistent output on all output media
while taking advantage of display hardware acceleration when available
(for example, through the X Render Extension).

The cairo API provides operations similar to the drawing operators of
PostScript and PDF. Operations in cairo including stroking and filling
cubic Bézier splines, transforming and compositing translucent images,
and antialiased text rendering. All drawing operations can be
transformed by any affine transformation (scale, rotation, shear,
etc.).

Cairo has been designed to let you draw anything you want in a modern
2D graphical user interface.  At the same time, the cairo API has been
designed to be as fun and easy to learn as possible. If you're not
having fun while programming with cairo, then we have failed
somewhere---let us know and we'll try to fix it next time around.

Cairo is free software and is available to be redistributed and/or
modified under the terms of either the GNU Lesser General Public
License (LGPL) version 2.1 or the Mozilla Public License (MPL) version
1.1.

Where to get more information about cairo
=========================================
The primary source of information about cairo is:

	http://cairographics.org/

The latest releases of cairo can be found at:

	http://cairographics.org/releases

Snapshots of in-development versions of cairo:

	http://cairographics.org/snapshots

The programming manual for using cairo:

	http://cairographics.org/manual

Mailing lists for contacting cairo users and developers:

	http://cairographics.org/lists

Answers to some frequently asked questions about cairo:

	http://cairographics.org/FAQ

Dependencies
============
The set of libraries needed to compile cairo depends on which backends
are enabled when cairo is configured. Here are the dependencies for
each backend:

Surface backends:

	image backend
	-------------
	no dependencies

	glitz backend
	-------------
	glitz >= 0.4.4 		http://freedesktop.org/Software/glitz

	pdf backend
	-----------
	freetype >= 2.1.4	http://freetype.org
	zlib			http://www.gzip.org/zlib

	postscript backend
	------------------
	freetype >= 2.1.4	http://freetype.org
	zlib			http://www.gzip.org/zlib

	quartz backend
	--------------
	[*]

	win32 backend
	-------------
	[*]

	xcb backend
	-----------
	XCB			http://xcb.freedesktop.org

	xlib backend
	------------
	Xrender >= 0.6		http://freedesktop.org/Software/xlibs

	beos backend
	------------
	No dependencies in itself other than an installed BeOS system, but cairo
	requires a font backend. See the freetype dependency list.

Font backends:

	freetype font backend
	---------------------
	freetype >= 2.1.4	http://freetype.org
	fontconfig		http://fontconfig.org

	win32 font backend
	------------------
	[*]

	atsui font backend
	------------------
	[*]

	[*] I don't know specifically what packages might need to be
	    installed on a Mac OS X system to use the Quartz and ATSUI
	    backends. As far as win32, the situation is rather complex:

	    The Win32 backend should work on Windows 2000 and newer
	    (excluding Windows Me.) Most testing has been done on
	    Windows XP. While some portions of the code have been
	    adapted to work on older versions of Windows, considerable
	    work still needs to done to get cairo running in these
	    environments.

	    Cairo can be compiled on Windows either with the GCC
	    toolchain (see http://www.mingw.org) or with Microsoft
	    Visual C++. Makefiles or project files for compiling with
	    MSVC are however not provided as of this release. We have
	    received reports that MSVC 6.0 compiles parts of cairo
	    incorrectly, (leading to incorrect color). MSVC 7.0 is
	    known to work.

Compiling
=========
See the INSTALL document for build instructions.

History
=======
Cairo was originally developed by Carl Worth <[e-mail]> and
Keith Packard <[e-mail]>. Many thanks are due to Lyle Ramshaw
without whose patient help our ignorance would be much more apparent.

Since the original development, many more people have contributed to
cairo. See the AUTHORS files for as complete a list as we've been able
to compile so far.