Cairo (graphics)

Last updated
Original author(s) Keith Packard, Carl Worth [1]
Developer(s) Carl Worth, Behdad Esfahbod
Initial releaseBefore 2003;21 years ago (2003) [2]
Stable release
1.18.0 (September 23, 2023;5 months ago (2023-09-23) [3] ) [±] }
Repository gitlab.freedesktop.org/cairo/cairo
Written in C
Type Graphics library
License GNU Lesser General Public License version 2.1 (only) or Mozilla Public License 1.1
Website www.cairographics.org

Cairo (stylized as cairo) is an open-source graphics library that provides a vector graphics-based, device-independent API for software developers. It provides primitives for two-dimensional drawing across a number of different backends. Cairo uses hardware acceleration [4] when available.

Contents

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# and other CLI languages, Delphi, Eiffel, Fortran, Factor, Harbour, Haskell, Julia, Lua, Perl, PHP, Python, Ruby, Rust, Scheme, Smalltalk and several others like Gambas (Visual Basic like). [5]

Toolkit bindings

Since Cairo is only a drawing library, it can be quite useful to integrate it with a graphical user interface toolkit.

Available back-ends

Cairo supports output (including rasterisation) to a number of different back-ends, known as "surfaces" in its code. Back-ends support includes output to the X Window System, via both Xlib and XCB, Win32 GDI, OS X Quartz Compositor, the BeOS API, OS/2, OpenGL contexts (directly [7] and via glitz), local image buffers, PNG files, PDF, PostScript, DirectFB and SVG files.

There are other back-ends in development targeting the graphics APIs OpenVG, [8] Qt, [9] Skia, [10] and Microsoft's Direct2D. [11] The BeOS, OS/2 and DirectFB backends were dropped in 2022. [12]

Drawing model

The Cairo drawing model Cairo's drawing model.svg
The Cairo drawing model

The Cairo drawing model relies on a three-layer model.

Any drawing process takes place in three steps:

  1. First a mask is created, which includes one or more vector primitives or forms, i.e., circles, squares, TrueType fonts, Bézier curves, etc.
  2. 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.
  3. 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 ] 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. [13]

Example

SVG picture generated by this example Cairo example.svg
SVG picture generated by this example

Quite complex "Hello world" graphics can be drawn with the help of Cairo with only a few lines of source code:

#include<cairo-svg.h>#include<stdio.h>intmain(intargc,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(intx=0;x<10;++x)for(inty=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);}

Notable usage

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

History

Keith Packard and Carl Worth founded the Cairo project for use in the X Window System. [2] 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. [22] The name Cairo derives from the original name Xr, interpreted as the Greek letters chi and rho. [23]

Complex text layout

Cairo handles Latin and CJK based fonts, but does not support complex text layout fonts, which require shaping the glyphs. [24]

See also

Related Research Articles

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References

  1. ↑ "Carl's boring web pages". cworth.org. 2013. Retrieved 11 July 2014.
  2. 1 2 "Xr: Cross-device Rendering for Vector Graphics" . Retrieved 2009-06-08.
  3. ↑ "Cairo 1.18 Released - First Stable Release In Five Years". www.phoronix.com. Retrieved 2023-09-23.
  4. ↑ "Cairo homepage" . Retrieved 2010-10-30.
  5. ↑ "Cairo Language Bindings" . Retrieved 2014-04-16.
  6. ↑ "SDL". Cairo. 2009-02-17. Retrieved 2014-11-03.
  7. ↑ Chris Wilson (2009-07-22). "New OpenGL backend merged" . Retrieved 2010-02-12.
  8. ↑ Øyvind Kolås (2008-01-24). "Announcing OpenVG backend" . Retrieved 2010-02-12.
  9. ↑ Vladimir Vukićević (2008-05-06). "Well Isn't That Qt". Archived from the original on 2010-04-09. Retrieved 2010-02-12.
  10. ↑ Chris Wilson (2009-08-31). "Cool Stuff" . Retrieved 2010-02-12.
  11. ↑ Bas Schouten (2009-11-22). "Direct2D: Hardware Rendering a Browser" . Retrieved 2010-02-12.
  12. ↑ Larabel, Michael (2022-02-27). "Cairo graphics library drops many old backends". Phoronix. Retrieved 2022-06-05.
  13. ↑ "GNOME/librsvg". GitHub.
  14. ↑ "GTK+ to Use Cairo Vector Engine" . Retrieved 2009-12-27.
  15. ↑ "Details of package gtk-vector-screenshot in stretch". Debian. GitHub
  16. ↑ "Mono - Drawing" . Retrieved 2009-12-27.
  17. ↑ "Moonlight Notes" . Retrieved 2009-12-27.
  18. ↑ "Gecko 1.9 Roadmap" . Retrieved 2009-12-27.
  19. ↑ "ReleaseNotes046". Inkscape Wiki. Retrieved 2008-03-31.
  20. ↑ "ManimCE tutorial by TheoremOfBeethoven — ManimCE tutorial by TB documentation". zavden.github.io. Retrieved 2023-01-29.
  21. ↑ "Gnuplot version 4.4.0 announcement". Gnuplot homepage. Archived from the original on 2011-05-14. Retrieved 2011-02-22.
  22. ↑ "Mailing list thread about the Cairo name change". 15 July 2003. Retrieved 2009-06-08.
  23. ↑ "Mailing list thread about the Cairo name change". 12 July 2003. Retrieved 2006-12-02.
  24. ↑ "Text". Readthedocs. Retrieved 2022-03-11.
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