Computer illustration or digital illustration is the use of digital tools to produce images under the direct manipulation of the artist, usually through a pointing device such as a tablet

Graphics tablet

A graphics tablet is a computer input device that enables a user to hand-draw images and graphics, similar to the way a person draws images with a pencil and paper. These tablets may also be used to capture data or handwritten signatures...

 or a mouse. It is distinguished from computer-generated art, which is produced by a computer using mathematical models created by the artist. It is also distinct from digital manipulation of photographs, in that it is an original construction "from scratch". (Photographic elements may be incorporated into such works, but they are not the primary basis or source for them.)

Pointing devices

Mice

Mouse (computing)

In computing, a mouse is a pointing device that functions by detecting two-dimensional motion relative to its supporting surface. Physically, a mouse consists of an object held under one of the user's hands, with one or more buttons...

 are not very precise for drawing, so a graphics tablet

Graphics tablet

A graphics tablet is a computer input device that enables a user to hand-draw images and graphics, similar to the way a person draws images with a pencil and paper. These tablets may also be used to capture data or handwritten signatures...

 is often preferred. A hybrid graphics tablet/screen would be optimal, since it gives the ability to see more accurately where the strokes are laid out in the image.

Illustration software

There are two main types of tools used for digital illustration: bitmap

Raster graphics

In computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...

ped and vector

Vector graphics

Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygon, which are all based on mathematical expressions, to represent images in computer graphics...

. With bitmapped tools, the content is stored digitally in fixed rows, columns, and layers, containing information about each pixel's hue, luminance, and sometimes filter settings. With vector-based tools, the content is stored digitally as resolution-independent mathematical formulae describing lines, shapes, and color gradients. Digital illustrations may include both raster and vector graphics in the same work.

Other programs - such as GraphicsMagick

GraphicsMagick

GraphicsMagick is a fork of ImageMagick, emphasizing stability of both programming API and command-line options. It was branched off ImageMagick's version 5.5.2 in 2002 after irreconcilable differences emerged in the developers' group....

, ImageMagick

ImageMagick

ImageMagick is an open source software suite for displaying, converting, and editing raster image files. It can read and write over 100 image file formats. ImageMagick is licensed under the Apache 2.0 license.- Features and capabilities:...

 and PhotoLine - have a more "programmatic approach" to illustration.

Online drawing

There are online drawing communities that allow people to draw include:

• drawball.com - the first collaborative canvas. main canvas is now locked.
• drawsum.com - anyone can draw on for free. collaborative. also has a facebook app.
• webcanvas.com - infinite collaborative canvas.
• Sumo Paint
  Sumo Paint
  Sumo Paint is a free online Flash-based image editor created in 2007, which is developed by Sumo Ltd., formerly Snap Group LLC. It is very similar to Photoshop, in that it features many of the same tools, but Sumo Paint is geared towards illustration, where other software such as Photoshop are more...
  
  - drawing tool and community.
• coloring4all.com
• Groupboard - multi-user java whiteboard, chat and conferencing.
• RateMyDrawings.com - Online drawing community.
• iScribble.net - draw with your friends online in real time.
• graffitiwall - a popular Facebook application, that allows users to draw on their or others profiles.
• Slimber.com - An online drawing application. Allows users to draw online, replay and save their drawings.
• deviantART muro - a professional art tool that features dynamic brushes, layers and multi-user collaboration. When finished, users can save their work either locally or online.