The Research Of Text Showing On Embedded Platform

With the advent of the information age, the display of text takes a large proportion in the output of digital devices. Therefore, how to deal with the display effectiveness of text, and continue to optimize it, has become a very important issue. The words processing technology has made substantial progress on the PC platform in the past few decades. There have been appear the dot-matrix'words, vector words and curve words. Because of it's limited resources, embedded system primarily use the dot matrix fonts to display text currently. On the other hand with the development of embedded technology, the display precision of output device on the embedded system is becoming higher. So it is difficult for the dot-matrix characters to meet the requirements of high-resolution display. Therefore, to replace the dot-matrix words and realize the display of TrueType fonts on high-definition products are the development trend of embedded technology. However, there is a lag problem for the display of subtitles srt when we use the open source TrueType engine, the FreeType libraries, on embedded high-definition movie player. This article focuse on the display of text on the embedded platform. It can be divided into two aspects: First, to improve and optimize the dot-matrix words display; Second, develop a efficient TrueType fonts driver to improve the quality of text display and promote product's upgrading.The main research work and results of this paper are as follows:(1) The display of dot-matrix words on embedded platform are very simple. This article mainly study the change processing for the dot-matrix words in order to enrich it's diversity on the high-definition player. It include scaling processing and contour modification. The latter will produce a black contour profile for the fonts to give prominence to their display.(2) To resolve the srt subtitles lag problem caused by the FreeType library, this paper proposes establishment memory database for glyf fonts. It can speed up the extraction process of fonts data, thereby increase the speed of display. Hense, the two key technologies in the development of TrueType driver are the establishment of indexes for fonts and the establishment memory database for fonts'glyf respectively. First, it need to establish local indexes which are consecutive for all the fonts; and then read the TrueType fonts file according to the indexes to get the size of data that needed to store, finally we allocate the corresponding memory and put the data into the memory to complete fonts'glyf memory database. In drawing text, convert the coding index to the local index and get the data from the memory database, the driver can draw the outline of the text, and then filled the area between the contour lines by scanning lines, finally, the TrueType fonts image can be seen.Test shows that if we scale the dot-matrix words limitly, the result is good and there is any distortion; while the contour modification can improve display greatly. What is more, the newly developed TrueType driver is stable and reliable. It not only can display the text clearly and beautifully, but also solve the srt subtitles lag problem when playback high-definition video. Hereby, it is ideal for resource-constrained embedded platforms.