Rasterisation

In 2D computer graphics called screening, also called rendering or scan conversion, the conversion of a vector in a raster graphics.

Method

There are a variety of algorithms for rasterization of graphic primitives such as lines, circles, and so on, see:

• Rasterization of lines
• Rasterization of polygons
• Screening of circles
• Screening of ellipses

A well-known problem of screening is the staircase effect. Represents to be generated raster graphics, a color depth of more than 1 bpp available, so this effect by means of " anti-aliasing " ( antialiasing) are reduced. There are several methods, some of which work unweighted, some use a special reconstruction filter. In the rasterization of text are facing specific problems that can be avoided by means of hinting.

Screening thicker primitives

In screening of primitives of a certain thickness, there is, provided it is not already supported by the anti-aliasing algorithm is used, a number of ways. Polygons here the connection between the individual line segments must be noted, refer to rasterization of polygons.

Deletion of primitives

Already drawn characters can be selectively deleted by being again drawn with the background color. However, this does not work if they overlap other figures, as this unwanted parts of the image can be deleted. An effective way of avoiding this, or minimax Boxing tests. Here, it is first checked whether in the plane spanned by the character to be deleted rectangle are other figures. Only if this is the case, tested for intersection and, optionally, the entire area to be redrawn.