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 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.) Mice are not very precise for drawing, so a graphics tablet 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.
There are two main types of tools used for digital illustration: bitmapped and vector. 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.