Glitz is a software library for 2D graphics

2D computer graphics

2D computer graphics is the computer-based generation of digital images—mostly from two-dimensional models and by techniques specific to them...

 which provides hardware acceleration

Hardware acceleration

In computing, Hardware acceleration is the use of computer hardware to perform some function faster than is possible in software running on the general-purpose CPU...

 using OpenGL

OpenGL

OpenGL is a standard specification defining a cross-language, cross-platform API for writing applications that produce 2D and 3D computer graphics. The interface consists of over 250 different function calls which can be used to draw complex three-dimensional scenes from simple primitives. OpenGL...

, an API

Application programming interface

An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...

 for 3D graphics

3D computer graphics

3D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images...

. Glitz is open-source software, licensed under (an old variant of) the MIT License

MIT License

The MIT License is a free software license originating at the Massachusetts Institute of Technology . It is a permissive license, meaning that it permits reuse within proprietary software provided all copies of the licensed software include a copy of the MIT License terms...

. Development is hosted at freedesktop.org

Freedesktop.org

freedesktop.org is a project to work on interoperability and shared base technology for free software desktop environments for the X Window System on Linux and other Unix-like operating systems. It was founded by Havoc Pennington from Red Hat in March 2000.The organisation focuses on the user....

, but has largely ceased.

Facilities provided

Glitz was designed to provide the same facilities as XRender

XRender

The X Rendering Extension is an X Window System extension to implement Porter-Duff image compositing in the X server, to allow efficient display of transparent images.- History :...

:

• Alpha compositing
  Alpha compositing
  In computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial or full transparency. It is often useful to render image elements in separate passes, and then combine the resulting multiple 2D images into a single, final image in a...
  
  
• Anti-aliasing
  Anti-aliasing
  In digital signal processing, spatial anti-aliasing is the technique of minimizing the distortion artifacts known as aliasing when representing a high-resolution image at a lower resolution...
  
  
• Subpixel rendering
  Subpixel rendering
  Subpixel rendering is a way to increase the apparent resolution of a computer's liquid crystal display or Organic Light Emitting Diode display by rendering pixels to take into account the screen type's physical properties...
  
  
• Rendering geometrical figures and text
• Geometric transformations such as translation
  Translation (geometry)
  In Euclidean geometry, a translation moves every point a constant distance in a specified direction. A translation can be described as a rigid motion, other rigid motions include rotations and reflections. A translation can also be interpreted as the addition of a constant vector to every point, or...
  
  , rotation
  Rotation
  A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...
  
   and scaling
  Scaling (geometry)
  In Euclidean geometry, uniform scaling is a linear transformation that enlarges or shrinks objects by a scale factor that is the same in all directions. The result of uniform scaling is similar to the original...
  
  

As with XRender, the key operation that Glitz provides is Porter-Duff composition

Alpha compositing

In computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial or full transparency. It is often useful to render image elements in separate passes, and then combine the resulting multiple 2D images into a single, final image in a...

.

Glitz also provides some facilities that XRender does not:

• Color gradient
  Color gradient
  In computer graphics, a color gradient specifies a range of position-dependent colors, usually used to fill a region. For example, many window managers allow the screen background to be specified as a gradient...
  
  s
• Convolution
  Convolution
  In mathematics and, in particular, functional analysis, convolution is a mathematical operation on two functions f and g, producing a third function that is typically viewed as a modified version of one of the original functions. Convolution is similar to cross-correlation...
  
   filters

All of this is implemented using OpenGL features such as multitexturing, shader

Shader

In the field of computer graphics, a shader is a computer program that is used primarily to calculate rendering effects on graphics hardware with a high degree of flexibility...

s, vertex buffers, frame buffer objects. In fact, a substantial part of Glitz is a wrapper around OpenGL that allows the programmer to think in terms of "drawable surfaces" rather than windows, pbuffers or frame buffer objects.

Software that uses Glitz

Glitz is the key component of the Xgl

Xgl

Xgl was an X server architecture designed to take advantage of modern graphics cards via their OpenGL drivers, layered on top of OpenGL via glitz. It supported hardware acceleration of all X, OpenGL and XVideo applications and graphical effects by a compositing window manager such as Compiz or...

 X server, which used to be shipped with most Linux distribution

Linux distribution

A Linux distribution is a member of the family of Unix-like operating systems built on top of the Linux kernel. Such distributions are operating systems including a large collection of software applications such as word processors, spreadsheets, media players, and database applications...

s. However, Xgl has now been mostly superseded by Accelerated Indirect GLX

AIGLX

Accelerated Indirect GLX is an open source project founded by Red Hat and the Fedora community, led by Kristian Høgsberg, to allow accelerated indirect GLX rendering capabilities to the X.Org Server and DRI drivers...

 (AIGLX).

The increasingly popular cairo graphics library supports Glitz as a backend

Front-end and back-end

Front end and back end are generalized terms that refer to the initial and the end stages of a process. The front end is responsible for collecting input in various forms from the user and processing it to conform to a specification the back end can use...

, meaning that a few lines of code will enable any of the applications and toolkits which use cairo to take advantage of graphics hardware. However, glitz support in cairo has bitrotted and does not work for the 1.8.x versions of cairo. Instead, future versions of Cairo will have an OpenGL backend.