Efficient coding of high resolution typographic characters

In modern phototypesetting equipments, it is necessary to digitize the typefonts with a very high resolution grid. An admissible typographic quality is obtained with a raster of 2048×2048 for a single character, leading thus to 4Mbits. In order to handle quickly a large number of styles in various typefonts of different size, it is mandatory to reduce this number a much as possible. Contour coding seems to be the most appropriate technique to achieve this goal. According to speed, memory size, quality, flexibility and simplicity criteria, expressing the contour in terms of line and circle segments seems to be an appropriate method. The number of segments necessary to approximate a large set of characters lies between 50 to 200. This leads to a compression ratio between 650:1 and 2600:1. Using the existing fast line and circle segment generation algorithms, a printing speed of 20 characters per second can be achieved at 2048×2048 resolution.