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Cairo (stylized as cairo) is an open-source
graphics library A graphics library is a program library designed to aid in rendering computer graphics to a monitor. This typically involves providing optimized versions of functions that handle common rendering tasks. This can be done purely in software and runn ...
that provides a
vector graphics Vector graphics is a form of computer graphics in which visual images are created directly from geometric shapes defined on a Cartesian plane, such as points, lines, curves and polygons. The associated mechanisms may include vector display ...
-based, device-independent
API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...
for software developers. It provides primitives for
two-dimensional In mathematics, a plane is a Euclidean ( flat), two-dimensional surface that extends indefinitely. A plane is the two-dimensional analogue of a point (zero dimensions), a line (one dimension) and three-dimensional space. Planes can arise as ...
drawing across a number of different back ends. Cairo uses hardware acceleration when available.


Software architecture


Language bindings

A library written in one programming language may be used in another language if bindings are written; Cairo has a range of bindings for various languages including
C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...
, C# and other
CLI languages CLI languages are computer programming languages that are used to produce libraries and programs that conform to the Common Language Infrastructure (CLI) specifications. With some notable exceptions, most CLI languages compile entirely to the Comm ...
, Delphi, Eiffel,
Factor Factor, a Latin word meaning "who/which acts", may refer to: Commerce * Factor (agent), a person who acts for, notably a mercantile and colonial agent * Factor (Scotland), a person or firm managing a Scottish estate * Factors of production, suc ...
, Harbour,
Haskell Haskell () is a general-purpose, statically-typed, purely functional programming language with type inference and lazy evaluation. Designed for teaching, research and industrial applications, Haskell has pioneered a number of programming lan ...
,
Julia Julia is usually a feminine given name. It is a Latinate feminine form of the name Julio and Julius. (For further details on etymology, see the Wiktionary entry "Julius".) The given name ''Julia'' had been in use throughout Late Antiquity (e.g ...
,
Lua Lua or LUA may refer to: Science and technology * Lua (programming language) * Latvia University of Agriculture * Last universal ancestor, in evolution Ethnicity and language * Lua people, of Laos * Lawa people, of Thailand sometimes referred t ...
,
Perl Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offic ...
,
PHP PHP is a general-purpose scripting language geared toward web development. It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. The PHP reference implementation is now produced by The PHP Group. ...
,
Python Python may refer to: Snakes * Pythonidae, a family of nonvenomous snakes found in Africa, Asia, and Australia ** ''Python'' (genus), a genus of Pythonidae found in Africa and Asia * Python (mythology), a mythical serpent Computing * Python (pro ...
,
Ruby A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called ...
,
Rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO( ...
, Scheme, Smalltalk and several others like
Gambas Gambas is the name of an object-oriented dialect of the BASIC programming language, as well as the integrated development environment that accompanies it. Designed to run on Linux and other Unix-like computer operating systems, its name is a re ...
(Visual Basic like).


Toolkit bindings

Since Cairo is only a drawing library, it can be quite useful to integrate it with a graphical user interface toolkit. * FLTK has full Cairo support (through --enable-cairo compile switch). *
GTK GTK (formerly GIMP ToolKit and GTK+) is a free and open-source cross-platform widget toolkit for creating graphical user interfaces (GUIs). It is licensed under the terms of the GNU Lesser General Public License, allowing both free and propriet ...
began in 2005, with version 2.8, to use Cairo to render the majority of its graphical control elements, and since version 3.0 all rendering is done through Cairo. * The Cairo development team maintains up-to-date instructions for rendering surfaces to SDL.


Available back-ends

Cairo supports output (including
rasterisation In computer graphics, rasterisation (British English) or rasterization (American English) is the task of taking an image described in a vector graphics format (shapes) and converting it into a raster image (a series of pixels, dots or lines, whi ...
) to a number of different back-ends, known as "surfaces" in its code. Back-ends support includes output to the
X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wi ...
, via both
Xlib Xlib (also known as libX11) is an X Window System protocol client library written in the C programming language. It contains functions for interacting with an X server. These functions allow programmers to write programs without knowing the ...
and
XCB XCB (''X protocol C-language Binding'') is a library implementing the client-side of the X11 display server protocol. XCB is written in the C programming language and distributed under the MIT License. The project was started in 2001 by B ...
, Win32 GDI, OS X Quartz Compositor, the BeOS API,
OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 r ...
, OpenGL contexts (directly and via glitz), local image buffers, PNG files, PDF, PostScript,
DirectFB DirectFB (Direct Frame Buffer) is a software library with a small memory footprint that provides graphics acceleration, input device handling and abstraction layer, and integrated windowing system with support for translucent windows and mult ...
and SVG files. There are other back-ends in development targeting the graphics APIs
OpenVG OpenVG is an application programming interface, API designed for Hardware acceleration, hardware-accelerated 2D computer graphics, 2D vector graphics. Its primary computing platform, platforms are mobile phones, gaming & media consoles and consume ...
, Qt, Skia, and Microsoft's
Direct2D Direct2D is a 2D vector graphics application programming interface (API) designed by Microsoft and implemented in Windows 10, Windows 8, Windows 7 and Windows Server 2008 R2, and also Windows Vista and Windows Server 2008 (with Platform Update i ...
. The BeOS, OS/2 and DirectFB backends were dropped in 2022.


Drawing model

The Cairo drawing model relies on a three-layer model. Any drawing process takes place in three steps: # First a mask is created, which includes one or more vector primitives or forms, i.e., circles, squares,
TrueType TrueType is an outline font standard developed by Apple in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript. It has become the most common format for fonts on the classic Mac OS, macOS, and Microsoft Windows operating ...
fonts, Bézier curves, etc. # Then source must be defined, which may be a color, a color gradient, a bitmap or some vector graphics, and from the painted parts of this source a die cut is made with the help of the above defined mask. # Finally the result is transferred to the destination or surface, which is provided by the back-end for the output. This constitutes a fundamentally different approach from
Scalable Vector Graphics Scalable Vector Graphics (SVG) is an XML-based vector image format for defining two-dimensional graphics, having support for interactivity and animation. The SVG specification is an open standard developed by the World Wide Web Consortium sinc ...
(SVG), which specifies the color of shapes with Cascading Style Sheets (CSS) rules. Whereas Cairo would create a mask of a shape, then make a source for it, and then transfer them onto the surface, an SVG file would simply specify the shape with a style attribute. That said, the models are not incompatible; many SVG renderers use Cairo for heavy lifting.


Example

Quite complex "
Hello world ''Hello'' is a salutation or greeting in the English language. It is first attested in writing from 1826. Early uses ''Hello'', with that spelling, was used in publications in the U.S. as early as the 18 October 1826 edition of the '' Norwich ...
" graphics can be drawn with the help of Cairo with only a few lines of
source code In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the w ...
: #include #include int main(int argc, char **argv)


Notable usage

Cairo is popular in the open source community for providing cross-platform support for advanced 2D drawing. *
GTK GTK (formerly GIMP ToolKit and GTK+) is a free and open-source cross-platform widget toolkit for creating graphical user interfaces (GUIs). It is licensed under the terms of the GNU Lesser General Public License, allowing both free and propriet ...
, starting in 2005 with version 2.8, uses Cairo to render the majority of its graphical control elements. Since GTK version 3, all the rendering is done using Cairo. ** A program called found in Debian allows for taking vector (SVG, PDF, or PostScript) screenshots of GTK 3 applications. * The
Mono Project Mono is a free and open-source .NET Framework-compatible software framework. Originally by Ximian, it was later acquired by Novell, and is now being led by Xamarin, a subsidiary of Microsoft and the .NET Foundation. Mono can be run on many softwa ...
, including Moonlight, has been using Cairo since very early in conception to power the back-ends of its
GDI+ The Graphics Device Interface (GDI) is a legacy component of Microsoft Windows responsible for representing graphical objects and transmitting them to output devices such as monitors and printers. Windows apps use Windows API to interact with G ...
(libgdiplus) and System.Drawing
namespaces In computing, a namespace is a set of signs (''names'') that are used to identify and refer to objects of various kinds. A namespace ensures that all of a given set of objects have unique names so that they can be easily identified. Namespaces ...
. * The
Mozilla Mozilla (stylized as moz://a) is a free software community founded in 1998 by members of Netscape. The Mozilla community uses, develops, spreads and supports Mozilla products, thereby promoting exclusively free software and open standards, w ...
project has made use of Cairo in its Gecko layout engine, used for rendering the graphical output of Mozilla products. Gecko 1.8, the layout engine for Mozilla Firefox 2.0 and
SeaMonkey SeaMonkey is a free and open-source Internet suite. It is the continuation of the former Mozilla Application Suite, based on the same source code, which itself grew out of Netscape Communicator and formed the base of Netscape 6 and Netscape ...
1.0, used Cairo to render SVG and content. Gecko 1.9, the release of Gecko that serves as the basis of
Firefox 3 Mozilla Firefox 3.0 is a version of the Firefox web browser released on June 17, 2008, by the Mozilla Corporation. Firefox 3.0 uses version 1.9 of the Gecko layout engine for displaying web pages. This version fixes many bugs, improves standard ...
, uses Cairo as the graphics back-end for rendering both web page content and the
user interface In the industrial design field of human–computer interaction, a user interface (UI) is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine f ...
(or "chrome"). * The
WebKit WebKit is a browser engine developed by Apple and primarily used in its Safari web browser, as well as on the iOS and iPadOS version of any web browser. WebKit is also used by the BlackBerry Browser, PlayStation consoles beginning from the P ...
framework uses Cairo for all rendering in the
GTK GTK (formerly GIMP ToolKit and GTK+) is a free and open-source cross-platform widget toolkit for creating graphical user interfaces (GUIs). It is licensed under the terms of the GNU Lesser General Public License, allowing both free and propriet ...
and EFL ports. Support has also been added for SVG and content using Cairo. * The Poppler library uses Cairo to render PDF documents. Cairo enables the drawing of antialiased vector graphics and transparent objects. * The vector graphics application
Inkscape Inkscape is a free and open-source vector graphics editor used to create vector images, primarily in Scalable Vector Graphics (SVG) format. Other formats can be imported and exported. Inkscape can render primitive vector shapes (e.g. rec ...
uses the Cairo library for its outline mode display, as well as for PDF and PostScript export since release 0.46. * Manim, a mathematical animation engine used in the animations of 3Blue1Brown's YouTube Videos. *
MorphOS MorphOS is an AmigaOS-like computer operating system (OS). It is a mixed proprietary and open source OS produced for the Pegasos PowerPC (PPC) processor based computer, PowerUP accelerator equipped Amiga computers, and a series of Freescale dev ...
2.5 features a shared library implementation of Cairo, which was available as stand-alone release for earlier MorphOS versions. *
AmigaOS AmigaOS is a family of proprietary native operating systems of the Amiga and AmigaOne personal computers. It was developed first by Commodore International and introduced with the launch of the first Amiga, the Amiga 1000, in 1985. Early versions ...
4.1 supports a shared object library of Cairo (libcairo.so) in its default installation. * FontForge enabled Cairo by default for rendering in mid-October 2008. * R can output plots in PDF, PostScript and SVG formats using Cairo if available. *
Gnuplot gnuplot is a command-line and GUI program that can generate two- and three-dimensional plots of functions, data, and data fits. The program runs on all major computers and operating systems (Linux, Unix, Microsoft Windows, macOS, FreeDOS, ...
4.4 now uses Cairo for rendering PDF and PNG output. * Internet Browser for PlayStation 3 uses Cairo since system software update 4.10. *
Synfig Synfig Studio (also known as Synfig) is a free and open-source vector-based 2D animation software. It is created by Robert Quattlebaum with additional contributions by Adrian Bentley. Synfig began as the custom animation platform for Voria Stu ...
0.64 now supports optional Cairo rendering. * On-demand graphing of time series data in
Graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on lar ...
. * The Konfabulator/Yahoo widget engine uses Cairo for identical output to both Win32 and Quartz on Mac OS/X. * SolveSpace, free and open source 2D and
3D CAD In 3D computer graphics, 3D modeling is the process of developing a mathematical coordinate-based representation of any surface of an object (inanimate or living) in three dimensions via specialized software by manipulating edges, vertices, an ...
software.


History

Keith Packard Keith Packard (born April 16, 1963) is a software developer, best known for his work on the X Window System. Packard is responsible for many X extensions and technical papers on X. He has been heavily involved in the development of X since the ...
and Carl Worth founded the Cairo project for use in the
X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wi ...
. It was originally (until at least 2003) called Xr or Xr/Xc. The name was changed to emphasize the idea of a cross-platform library to access
display server In computing, a windowing system (or window system) is software that manages separately different parts of display screens. It is a type of graphical user interface (GUI) which implements the WIMP (windows, icons, menus, pointer) paradigm for ...
, not tied to the
X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wi ...
. The name ''Cairo'' derives from the original name ''Xr'', interpreted as the Greek letters chi and
rho Rho (uppercase Ρ, lowercase ρ or ; el, ρο or el, ρω, label=none) is the 17th letter of the Greek alphabet. In the system of Greek numerals it has a value of 100. It is derived from Phoenician letter res . Its uppercase form uses the sa ...
.


Complex text layout

Cairo handles Latin and CJK based fonts, but does not support
complex text layout Complex text layout (CTL) or complex text rendering is the typesetting of writing systems in which the shape or positioning of a grapheme depends on its relation to other graphemes. The term is used in the field of software internationalizatio ...
fonts, which require shaping the glyphs.


See also

*
Display PostScript Display PostScript (or DPS) is a 2D graphics engine system for computers which uses the PostScript (PS) imaging model and language (originally developed for computer printing) to generate on-screen graphics. To the basic PS system, DPS adds a num ...
and Quartz 2D *
Skia Graphics Engine The Skia Graphics Engine or Skia is an open-source 2D graphics library written in C++. Skia abstracts away platform-specific graphics API (which differ from one to another). Skia Inc. originally developed the library; Google acquired it in 2005, ...
*
Starling Framework Starling is an open source game framework used to create 2D games that run both on mobile and desktop platforms. It recreates the traditional Flash display list architecture on top of accelerated graphics hardware. Several commercial games have ...
*
WebGL WebGL (Short for Web Graphics Library) is a JavaScript API for rendering interactive 2D and 3D graphics within any compatible web browser without the use of plug-ins. WebGL is fully integrated with other web standards, allowing GPU-accelera ...
* ThorVG


References


External links

* * – CFFI-based Cairo bindings for Python * * * * * {{Freedesktop.org Free computer libraries Free software programmed in C Freedesktop.org Freedesktop.org libraries GNOME libraries GTK Software using the LGPL license Software using the Mozilla license