Truetype Font Engine

The technique dealing with information of computer font is the special domain which researches how to describe, store and output font symbol in different form on the computer. From the seventies of the last century, the computer broke through the simple calculating application in science calculating and disposing data. It can be used to transaction processing, word processing and so on. And there is a problem that how to store the kinds of words. So the digital font plays an important role in the development of the computer applications. Along with the appearance and development of the raster equipment, as the important part of the technique dealing with information of computer font, the technique is laid store by people, which is used to revert and output the computer font.Result of the wild use of the TrueType font, the TrueType font engine is main member in the font engine family and important part in the printer driver, which transforms the characters described by TrueType font into bitmap. There is the significance to investigate and implement the TrueType font engine. Meanwhile it is more agility and useful because of it is independent of Microsoft font engine, which is advanced by this disquisition.For this purpose, this disquisition introduced the TrueType technique and the basic structure of the TrueType file. Proceed with this we research the key concepts about the TrueType font engine. At last we found out a design of the TrueType font engine, which is dependent of Microsoft font engine and can also be used in printer driver.As a member of the project group, I participated in the whole design of the project and all analysis of the datum. Then I am with responsibility for the design and implement the raster module.In this process, I improved on the traditional polygon scan line filling algorithm in reasons, base on the reaching of the algorithm which be used to judge the points which are inside the outline or not. In the end I found out a design of the polygon scan line filling algorithm, which applies to TrueType font character outlines that may be cross between outlines. It has several characteristics. One of them is scanning vertically and horizontally. It can improve filling precision and predigest disposal. Another one is "virtually portrayal". It can record the vertexes of the outline and the cross points between outlines and scan lines. And more important point is that it can record the direction when the scan line crosses the outline. With this information we can use winding number easily.