The TrueType font technology consists of two parts: the description of the fonts themselves (the TrueType font files), and the program which reads the font description and generates the bitmaps (the TrueType Rasterizer).

The TrueType Rasterizer is a computer program which is typically incorporated as part of an operating system or printer control software. With this in mind, it has been written with a well defined client interface, and a clean modular structure in portable C.

The job of the TrueType Rasterizer is to generate character bitmaps for screens and printers (otherwise known as raster devices). It accomplishes this by performing the following tasks:

• Reading the outline description of the character (lines and splines) from the TrueType font file.
• Scaling the outline description of the character to the requested size and device resolution.
• Adjusting the outline description to the pixel grid (based on hinting information).
• Filling the adjusted outline with pixels (scan conversion).