Editing Cairo (graphics)

{{Short description|Vector graphics-based software library}}
{{DISPLAYTITLE:cairo (graphics)}}
{{Use mdy dates|date=October 2024}}
{{Infobox software
| name                   = Cairo
| title                  = 
| logo                   = Cairo banner closeup.svg
| logo size              = 150px
| logo caption           = [[File:Cairo graphics.svg|125px]]
| screenshot             =
| caption                =
| collapsible            =
| author                 = [[Keith Packard]], Carl Worth<ref>{{cite web |url= http://cworth.org/ |title=Carl's boring web pages  |work=cworth.org |year=2013 |access-date=July 11, 2014}}</ref>
| developer              = Carl Worth, [[Behdad Esfahbod]]
| released               = Before {{Start date and age|2003}}<ref name=xrols2003>{{cite web | title=Xr: Cross-device Rendering for Vector Graphics | url=http://cworth.org/~cworth/papers/xr_ols2003/html/ | access-date=June 8, 2009}}</ref>
| discontinued           =
| latest release version = {{Latest stable software release/cairo}}
| latest_preview_version =
| latest_preview_date =
| programming language   = [[C (programming language)|C]]
| operating system       = <!--Does not apply-->
| platform               = <!--Does not apply-->
| size                   =
| language               =
| language count         =
| language footnote      =
| status                 =
| genre                  = [[Graphics library]]
| license                = [[GNU Lesser General Public License]] version 2.1 (only) or [[Mozilla Public License]] 1.1
| alexa                  =
| website                = {{URL|https://www.cairographics.org}}
| repo                   = {{URL|https://gitlab.freedesktop.org/cairo/cairo}}
}}

'''Cairo''' (stylized as '''cairo''') is an [[Open-source software|open-source]] [[graphics library]] that provides a [[vector graphics]]-based, device-independent [[Application programming interface|API]] for [[software developer]]s. It provides primitives for [[Plane (mathematics)|two-dimensional]] drawing across a number of different [[front and back ends|backends]]. Cairo uses [[hardware acceleration]]<ref>{{cite web | url = http://cairographics.org/ | title = Cairo homepage | access-date = October 30, 2010}}</ref> when available.

== Software architecture ==
=== Language bindings ===
A library written in one programming language may be used in another language if [[language binding|bindings]] are written; Cairo has a range of bindings for various languages including [[C++]], [[C Sharp (programming language)|C#]] and other [[Common Language Infrastructure|CLI languages]], [[Delphi (programming language)|Delphi]], [[Eiffel (programming language)|Eiffel]], [[Fortran]], [[Factor (programming language)|Factor]], [[Harbour (programming language)|Harbour]], [[Haskell (programming language)|Haskell]], [[Julia (programming language)|Julia]], [[Lua (programming language)|Lua]], [[Perl]], [[PHP]], [[Python (programming language)|Python]], [[Ruby (programming language)|Ruby]], [[Rust (programming language)|Rust]], [[Scheme (programming language)|Scheme]], [[Smalltalk]] and several others like [[Gambas]] (Visual Basic like).<ref>{{cite web |url=http://cairographics.org/bindings/ |title=Cairo Language Bindings |access-date=April 16, 2014}}</ref>

=== 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 <code>--enable-cairo</code> compile switch).
* [[GTK]] began in 2005, with version 2.8, to use Cairo to render the majority of its [[Graphical control element (software)|graphical control elements]], and since version 3.0 all [[rendering (computer graphics)|rendering]] is done through Cairo.
* The Cairo development team maintains up-to-date instructions for rendering surfaces to [[Simple DirectMedia Layer|SDL]].<ref>{{cite web |url=http://cairographics.org/SDL/ |title=SDL |website=Cairo |date=February 17, 2009 |access-date=November 3, 2014}}</ref>

=== Available back-ends ===
Cairo supports output (including [[rasterisation]]) to a number of different [[front and back ends|back-ends]], known as "surfaces" in its code. Back-ends support includes output to the [[X Window System]], via both [[Xlib]] and [[XCB]], [[Graphics Device Interface|Win32 GDI]], [[Quartz Compositor|OS X Quartz Compositor]], the [[BeOS]] API, [[OS/2]], [[OpenGL]] contexts (directly<ref>{{cite web |url=http://lists.cairographics.org/archives/cairo/2009-July/017713.html |title=New OpenGL backend merged |author=Chris Wilson |date=July 22, 2009 |access-date=February 12, 2010}}</ref> and via glitz), local image buffers, [[Portable Network Graphics|PNG]] files, [[Portable document format|PDF]], [[PostScript]], [[DirectFB]] and [[Scalable Vector Graphics|SVG]] files.

There are other back-ends in development targeting the graphics APIs [[OpenVG]],<ref>{{cite web |url=http://lists.freedesktop.org/archives/cairo/2008-January/012833.html |title=Announcing OpenVG backend |author=Øyvind Kolås |date=January 24, 2008 |access-date=February 12, 2010}}</ref> [[Qt (framework)|Qt]],<ref>{{cite web |url=http://blog.vlad1.com/2008/05/06/well-isnt-that-qt/ |title=Well Isn't That Qt |author=Vladimir Vukićević |date=May 6, 2008 |access-date=February 12, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100409072817/http://blog.vlad1.com/2008/05/06/well-isnt-that-qt/ |archive-date=April 9, 2010}}</ref> [[Skia Graphics Engine|Skia]],<ref>{{cite web |url=http://lists.cairographics.org/archives/cairo/2009-August/018052.html |title=Cool Stuff |author=Chris Wilson |date=August 31, 2009 |access-date=February 12, 2010}}</ref> and Microsoft's [[Direct2D]].<ref>{{cite web |url=http://www.basschouten.com/blog1.php/2009/11/22/direct2d-hardware-rendering-a-browser |title=Direct2D: Hardware Rendering a Browser |author=Bas Schouten |date=November 22, 2009 |access-date=February 12, 2010}}</ref> The BeOS, OS/2, DirectFB and OpenGL backends were dropped in 2022.<ref>{{cite web|url=https://www.phoronix.com/scan.php?page=news_item&px=Cairo-2022-Drops-Old-Code|title=Cairo graphics library drops many old backends|first=Michael|last=Larabel|publisher=Phoronix|date=February 27, 2022|accessdate=June 5, 2022}}</ref><ref>{{cite web |last1=Larabel |first1=Michael |title=Cairo Graphics Library Drops OpenGL Support After A Decade Of Inactivity |url=https://www.phoronix.com/news/Cairo-Drops-OpenGL |website=Phoronix |access-date=7 February 2025 |date=January 29, 2023}}</ref>

=== Drawing model ===
[[File:Cairo's drawing model.svg|thumb|The Cairo 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]] fonts, [[Bézier curve]]s, 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]] (SVG), which specifies the color of shapes with [[Cascading Style Sheets]] (CSS) rules.{{Citation needed|date=September 2021}} 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 <code>style</code> attribute. That said, the models are not incompatible; many SVG renderers use Cairo for heavy lifting.<ref>{{cite web |url=https://github.com/GNOME/librsvg |title=GNOME/librsvg |website=GitHub}}</ref><!-- Well, SVG 1.1. in fact provides a way to achieve similar result via filters. Checkout: https://www.w3.org/TR/SVG11/filters.html -->

==== Example ====
Quite complex "[[Hello world program|Hello world]]" graphics can be drawn with the help of Cairo with only a few lines of [[source code]]:
[[File:Cairo example.svg|thumb|none|180px|SVG picture generated by this example]]
<syntaxhighlight line lang="c">
#include <cairo-svg.h>
#include <stdio.h>

int main(int argc, char **argv) {
    cairo_surface_t *surface = cairo_svg_surface_create("Cairo_example.svg", 100.0, 100.0);
    cairo_t *cr = cairo_create(surface);

    /* Draw the squares in the background */
    for (int x = 0; x < 10; ++x)
        for (int y = 0; y < 10; ++y)
            cairo_rectangle(cr, x * 10.0, y * 10.0, 5, 5);

    cairo_pattern_t *pattern = cairo_pattern_create_radial(50, 50, 5, 50, 50, 50);
    cairo_pattern_add_color_stop_rgb(pattern, 0, 0.75, 0.15, 0.99);
    cairo_pattern_add_color_stop_rgb(pattern, 0.9, 1, 1, 1);

    cairo_set_source(cr, pattern);
    cairo_fill(cr);

    /* Writing in the foreground */
    cairo_set_font_size (cr, 15);
    cairo_select_font_face (cr, "Georgia", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_BOLD);
    cairo_set_source_rgb (cr, 0, 0, 0);

    cairo_move_to(cr, 10, 25);
    cairo_show_text(cr, "Hallo");

    cairo_move_to(cr, 10, 75);
    cairo_show_text(cr, "Wikipedia!");

    cairo_destroy(cr);
    cairo_surface_destroy(surface);
}
</syntaxhighlight>

== Notable usage ==
Cairo is popular in the open source community for providing cross-platform support for advanced 2D drawing.

* [[GTK]], starting in 2005 with version 2.8, uses Cairo to render the majority of its [[Graphical control element (software)|graphical control elements]].<ref>{{cite web |url=http://developers.slashdot.org/article.pl?sid=05/02/04/2021236 |title=GTK+ to Use Cairo Vector Engine |date=February 5, 2005 |access-date=December 27, 2009}}</ref> Since GTK version 3, all the rendering is done using Cairo.
** A program called {{tt|gtk-vector-screenshot}} found in [[Debian]] allows for taking vector (SVG, PDF, or PostScript) [[screenshot]]s of GTK 3 applications.<ref>{{cite web |title=Details of package gtk-vector-screenshot in stretch |url=https://packages.debian.org/stretch/gtk-vector-screenshot |website=Debian}} [https://github.com/nomeata/gtk-vector-screenshot GitHub]</ref>
* The [[Mono (software)|Mono Project]],<ref>{{cite web |url=http://www.mono-project.com/Drawing |title=Mono - Drawing |access-date=December 27, 2009}}</ref> including [[Moonlight (runtime)|Moonlight]],<ref>{{cite web |url=http://www.mono-project.com/MoonlightNotes#Rendering |title=Moonlight Notes |access-date=December 27, 2009}}</ref> has been using Cairo since very early in conception to power the back-ends of its [[GDI+]] (libgdiplus) and System.Drawing [[namespaces]].
* The [[Mozilla]] project has made use of Cairo in its [[Gecko (software)|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]] 1.0, used Cairo to render SVG and [[Canvas element|<canvas>]] content. Gecko 1.9,<ref>{{cite web |url=https://wiki.mozilla.org/Gecko_1.9_Roadmap#cairo_Graphics_Substrate |title=Gecko 1.9 Roadmap |access-date=December 27, 2009}}</ref> the release of Gecko that serves as the basis of [[Mozilla Firefox 3|Firefox 3]], uses Cairo as the graphics back-end for rendering both web page content and the [[user interface]] (or "chrome").
* The [[WebKit]] framework uses Cairo for all rendering in the [[GTK]] and [[Enlightenment Foundation Libraries|EFL]] ports. Support has also been added for SVG and <canvas> content using Cairo.{{cn|date=October 2024}}
* The [[Poppler (software)|Poppler]] library uses Cairo to render PDF documents. Cairo enables the drawing of antialiased vector graphics and transparent objects.{{cn|date=October 2024}}
* The vector graphics application [[Inkscape]] uses the Cairo library for its outline mode display, as well as for [[Portable Document Format|PDF]] and [[PostScript]] export since release 0.46.<ref>{{cite web |url=http://wiki.inkscape.org/wiki/index.php/ReleaseNotes046 |title=ReleaseNotes046 |work=Inkscape Wiki |access-date=March 31, 2008}}</ref>
* The original version of [[Manim]] referred to as ManimCairo, a mathematical animation engine used in the animations of 3Blue1Brown's YouTube Videos. Manim has since moved to using [[OpenGL]]. This version is referred to as ManimGL.<ref>{{Cite web |title=ManimCE tutorial by TheoremOfBeethoven — ManimCE tutorial by TB documentation |url=https://zavden.github.io/manimce-tutorial/docs/html/index.html |access-date=January 29, 2023 |website=zavden.github.io}}</ref>
* [[MorphOS]] 2.5 features a shared library implementation of Cairo, which was available as stand-alone release for earlier MorphOS versions.{{cn|date=October 2024}}
* [[AmigaOS]] 4.1 supports a shared object library of Cairo (libcairo.so) in its default installation.{{cn|date=October 2024}}
* [[FontForge]] enabled Cairo by default for rendering in mid-October 2008.{{cn|date=October 2024}}
* [[R (programming language)|R]] can output plots in [[Portable Document Format|PDF]], [[PostScript]] and [[Scalable Vector Graphics|SVG]] formats using Cairo if available.{{cn|date=October 2024}}
* [[Gnuplot]] 4.4 now uses Cairo for rendering [[Portable Document Format|PDF]] and [[Portable Network Graphics|PNG]] output.<ref>{{cite web | url = http://www.gnuplot.info/announce.4.4.0 | title = Gnuplot version 4.4.0 announcement | work = Gnuplot homepage | access-date = February 22, 2011 | archive-url = https://web.archive.org/web/20110514115341/http://www.gnuplot.info/announce.4.4.0 | archive-date = May 14, 2011 | url-status = dead }}</ref>
* Internet Browser for PlayStation 3 uses Cairo since system software update 4.10.{{cn|date=October 2024}}
* [[Synfig]] 0.64 now supports optional Cairo rendering.{{cn|date=October 2024}}
* On-demand graphing of time series data in [[Graphite (software)|Graphite]].{{cn|date=October 2024}}
* The Konfabulator/Yahoo widget engine uses Cairo for identical output to both Win32 and Quartz on [[Mac OS/X]].{{cn|date=October 2024}}
*[[SolveSpace]], free and open source 2D and [[3D CAD]] software.{{cn|date=October 2024}}

== History ==
[[Keith Packard]] and Carl Worth founded the Cairo project for use in the [[X Window System]].<ref name=xrols2003 /> 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]], not tied to the [[X Window System]].<ref>
{{cite web | title=Mailing list thread about the Cairo name change | date=July 15, 2003 | url=http://lists.cairographics.org/archives/cairo/2003-July/000192.html | access-date=June 8, 2009}}</ref>
The name ''Cairo'' derives from the original name ''Xr'', interpreted as the Greek letters [[chi (letter)|chi]] and [[rho (letter)|rho]].<ref>
{{cite web | title=Mailing list thread about the Cairo name change | date=July 12, 2003 | url=http://lists.freedesktop.org/archives/cairo/2003-July/000184.html | access-date=December 2, 2006}}
</ref>
==Complex text layout==
Cairo handles Latin and CJK based fonts, but does not directly support [[complex text layout]] fonts, which require shaping the glyphs. The Cairo developers recommend using [[Pango]], which provides complex text layout and can integrate with Cairo.<ref>{{Cite web | url=https://www.cairographics.org/FAQ/#using_pango | title=How do I use Pango instead of Cairo's "toy" text API? | access-date=March 20, 2024}}</ref>

== See also ==
{{Portal|Free and open-source software}}
* [[Display PostScript]] and [[Quartz 2D]]
* [[Skia Graphics Engine]]
* [[Starling Framework]]
* [[WebGL]]

== References ==
{{Reflist|30em}}

== External links ==
{{Commons category}}
* {{Official website|https://www.cairographics.org}}
* {{github|SimonSapin/cairocffi}} – CFFI-based Cairo bindings for Python
* {{cite web | url = http://cairographics.org/manual/ | title = Cairo API reference manual}}
* {{cite web | work = Linux.Ars | url = https://arstechnica.com/articles/columns/linux/linux-20050822.ars | title = Cairo here, there and everywhere | date = August 23, 2005 | publisher = [[Ars Technica]]}}
* {{cite web | url = http://www.ibm.com/developerworks/linux/library/l-cairo/ | title = Cross-platform graphics with cairo| website = [[IBM]]}}
* {{cite web | url = http://kore-nordmann.de/blog/comparision_of_php_image_libraries.html | title = Comparison of PHP image libraries}}
* {{cite web | url = http://zetcode.com/gfx/cairo/ | title = The Cairo graphics tutorial}}

{{Freedesktop.org}}

[[Category:Cairo (graphics)| ]]
[[Category:Free computer libraries]]
[[Category:Free software programmed in C]]
[[Category:Freedesktop.org]]
[[Category:Freedesktop.org libraries]]
[[Category:GNOME libraries]]
[[Category:GTK]]
[[Category:Software using the GNU Lesser General Public License]]
[[Category:Software using the Mozilla Public License]]