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ClearType is Microsoft's implementation of subpixel rendering technology in rendering text in a font system. ClearType attempts to improve the appearance of text on certain types of computer display screens by sacrificing color fidelity for additional intensity variation. This trade-off is asserted to work well on LCD flat panel monitors. ClearType was first announced at the November 1998 COMDEX exhibition. The technology was first introduced in software in January 2000 as an always-on feature of Microsoft Reader, which was released to the public in August 2000. ClearType was significantly changed with the introduction of DirectWrite in Windows 7. ==Background== Computer displays where the positions of individual pixels are permanently fixed—such as most modern flat panel displays—can show saw-tooth edges when displaying small, high-contrast graphic elements, such as text. ClearType uses spatial anti-aliasing at the subpixel level to reduce visible artifacts on such displays when text is rendered, making the text appear "smoother" and less jagged. ClearType also uses very heavy font hinting to force the font to fit into the pixel grid. This increases edge contrast and readability of small fonts at the expense of font rendering fidelity and has been criticized by graphic designers for making different fonts look similar . Like most other types of subpixel rendering, ClearType involves a compromise, sacrificing one aspect of image quality (color or ''chrominance'' detail) for another (light and dark or ''luminance'' detail). The compromise can improve text appearance when luminance detail is more important than chrominance. Only user and system applications render application of ClearType. ClearType does not alter other graphic display elements (including text already in bitmaps). For example, ClearType enhancement renders text on the screen in Microsoft Word, but text placed in a bitmapped image in a program such as Adobe Photoshop is not. In theory, the method (called "RGB Decimation" internally) can enhance the anti-aliasing of any digital image.〔Betrisey et al., "Displaced Filtering for Patterned Displays", Proc. Society for Information Display Symposium, 2000〕 ClearType is not used when printing text. Most printers already use such small pixels that aliasing is rarely a problem, and they don't have the addressable fixed subpixels ClearType requires. Nor does ClearType affect text stored in files. ClearType only applies any processing to the text while it is being rendered onto the screen. ClearType was invented in the Microsoft e-Books team by Bert Keely and Greg Hitchcock. It was then analyzed by researchers in the company, and signal processing expert John Platt designed an improved version of the algorithm.〔Platt, J.C., "(Optimal Filtering for Patterned Displays )", IEEE Signal Processing Letters, 7(7), 2000, pp. 179-180〕 Dick Brass, a Vice President at Microsoft from 1997 to 2004, complained that the company was slow in moving ClearType to market in the portable computing field.〔(Microsoft’s Creative Destruction )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ClearType」の詳細全文を読む スポンサード リンク
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