信息技术.视听对象编码.第22部分:开放字体格式

[中文适用范围]： 本部分规定了开放字体格式（OFF）规范、TrueType 和紧凑字体格式（CFF）轮廓格式以及 TrueType 提示语言。文档中大量引用了 TrueType 和 PostScript，因为开放字体格式字体结合了这两种技术。注：本规范基于 OpenType 字体格式规范，在技术上与该规范等效。多媒体应用程序需要广泛的多媒体相关标准。除了典型的音频和视频应用程序外，多媒体演示还包括支持全球所有语言的 2D 图形和文本。忠实再现可缩放的 multimedia 内容需要额外的组件，包括可缩放字体技术。开放字体格式是 TrueType 字体格式的扩展，增加了对 PostScript 字体数据的支持。OFF 字体和操作系统服务使用户能够简单地安装和使用字体，无论字体包含 TrueType 轮廓还是 CFF（PostScript）轮廓。开放字体格式旨在实现以下目标：更广泛的跨平台支持；对国际字符集的出色支持；对字体数据的出色保护；更小的文件大小以提高字体分发的效率；对高级排版控制的出色支持。包含在 OFF 字体中的 PostScript 数据可以直接光栅化或转换为 TrueType 轮廓格式进行渲染，具体取决于主机操作系统中安装的光栅化器。但用户模型是相同的：OFF 字体即插即用。用户无需了解 OFF 字体中轮廓数据的类型。字体创作者可以使用他们认为能提供最佳功能集的轮廓格式，而无需担心限制字体的可用性。OFF 字体可以包含 OFF 布局表，允许字体创作者设计更广泛的国际和高端排版字体。OFF 布局表包含字形替换、字形定位、对齐和基线定位的信息，使文本处理应用程序能够改进文本布局。与 TrueType 字体一样，OFF 字体允许使用 Unicode 编码处理大型字形集。这种编码允许广泛的国际支持，以及对排版字形变体的支持。此外，OFF 字体可以包含数字签名，使操作系统和浏览应用程序能够在使用字体文件（包括从 Web 文档中获得的嵌入字体）之前识别字体文件的来源和完整性。字体开发者还可以编码嵌入限制，这些限制在开发者签名的字体中无法更改。 [外文原描述]： ISO/IEC 14496-22:2009 specifies the Open Font Format (OFF) specification, the TrueType™ and Compact Font Format (CFF) outline formats, and the TrueType hinting language. It makes references to both TrueType and PostScript, as Open Font Format fonts combine the two technologies. Multimedia applications require a broad range of media-related standards. In addition to the typical audio and video applications, multimedia presentations include scalable 2D graphics and text supporting all languages of the world. Faithful reproduction of scalable multimedia content requires additional components including scalable font technology. The Open Font Format is an extension of the TrueType font format, adding support for PostScript font data. OFF fonts and the operating system services which support OFF fonts provide users with a simple way to install and use fonts, whether the fonts contain TrueType outlines or CFF (PostScript) outlines. The Open Font Format addresses the following goals: broader multi-platform support; excellent support for international character sets; excellent protection for font data; smaller file sizes to make font distribution more efficient; excellent support for advanced typographic control. PostScript® data included in OFF fonts may be directly rasterized or converted to the TrueType outline format for rendering, depending on which rasterizers have been installed in the host operating system. But the user model is the same: OFF fonts just work. Users will not need to be aware of the type of outline data in OFF fonts. And font creators can use whichever outline format they feel provides the best set of features for their work, without worrying about limiting a font's usability. OFF fonts can include the OFF Layout tables, which allow font creators to design broader international and high-end typographic fonts. The OFF Layout tables contain information on glyph substitution, glyph positioning, justification, and baseline positioning, enabling text-processing applications to improve text layout. As with TrueType fonts, OFF fonts allow the handling of large glyph sets using Unicode encoding. Such encoding allows broad international support, as well as support for typographic glyph variants. Additionally, OFF fonts may contain digital signatures, which enable operating systems and browsing applications to identify the source and integrity of font files, including embedded font files obtained in web documents, before using them. Also, font developers can encode embedding restrictions in OFF fonts which cannot be altered in a font signed by the developer.