信息技术 计算机图形 存储和传送图片描述信息的元文卷 第1部分:功能规范

[中文适用范围]： ISO/IEC 8632 提供了适合存储和检索图片描述信息的文件格式。 文件格式由一组有序的元素组成，这些元素可用于以在不同体系结构的系统之间兼容、与不同功能和设计的设备兼容并且对应用程序群体有意义的方式来描述图片。 该图片描述包括描述静态图像的能力。 指定的元素提供了在各种图形设备上表示各种图片。 这些元素被组织成组，这些组界定主要结构（图元文件、图片和应用程序结构），指定图元文件中使用的表示形式，控制图片的显示，执行基本绘图操作，控制基本图形的属性。 绘图操作，允许将特定于应用程序的结构叠加在图形内容上，并提供对非标准设备功能的访问。 图元文件的定义方式是，除了对整个图元文件的顺序访问之外，还明确定义了对各个图片和各个上下文无关的应用程序结构的随机访问。 需要随机访问图片和/或图片内的上下文无关的应用程序结构的应用程序可以在元文件内定义这些图片和/或上下文无关的应用程序结构的目录。 然后可以打开并随机访问图元文件，而无需解释整个图元文件。 除了功能规范之外，还指定了图元文件语法的两种标准编码。 这些编码满足了需要较小图元文件大小、生成和解释最少工作量以及图元文件人类读者或编辑者最大灵活性的应用程序的需求。 ISO/IEC 8632 的这一部分使用抽象语法描述了格式。 ISO 8632 的其余部分指定了符合此语法的标准化编码： ISO/IEC 8632-3 指定了二进制编码； ISO/IEC 8632-4 指定了明文编码。 [外文原描述]： ISO/IEC 8632 provides a file format suitable for the storage and retrieval of picture description information. The file format consists of an ordered set of elements that may be used to describe pictures in a way that is compatible between systems of different architectures, compatible with devices of differing capabilities and design, and meaningful to application constituencies. This picture description includes the capability for describing static images. The elements specified provide for the representation of a wide range of pictures on a wide range of graphical devices. The elements are organized into groups that delimit major structures (metafiles, pictures, and application structures), that specify the representations used within the metafile, that control the display of the picture, that perform basic drawing actions, that control the attributes of the basic drawing actions, that allow application-specific structuring to be overlaid on the graphical content, and that provide access to non-standard device capabilities. The metafile is defined in such a way that, in addition to sequential access to the whole metafile, random access to individual pictures and individual context-independent application structures is well-defined. Applications which require random access to pictures and/or context-independent application structures within pictures may, within the metafile, define directories to these pictures and/or context-independent application structures. The metafile may then be opened and randomly accessed without interpreting the entire metafile. In addition to a functional specification, two standard encodings of the metafile syntax are specified. These encodings address the needs of applications that require small metafile size plus minimum effort to generate and interpret, and maximum flexibility for a human reader or editor of the metafile. This part of ISO/IEC 8632 describes the format using an abstract syntax. The remaining parts of ISO 8632 specify standardized encodings that conform to this syntax: ISO/IEC 8632-3 specifies a binary encoding; ISO/IEC 8632-4 specifies a clear text encoding.