14.2 程序集¶
14.2 Procedure Sets
内容流中使用的PDF操作符被分组为相关操作符的类别，称为程序集（见表314）。每个程序集对应一个命名资源，其中包含该程序集中操作符的实现。内容流资源字典中的ProcSet条目（见7.8.3，“资源字典”）应包含一个数组，该数组由该内容流中使用的程序集的名称组成。这些程序集仅在内容流打印到PostScript输出设备时使用。名称标识应发送到设备以解释内容流中的PDF操作符的PostScript程序集。该数组的每个元素应为表314中显示的预定义名称之一。
| 名称 | 操作符类别 |
|---|---|
| 绘图和图形状态 | |
| Text | 文本 |
| ImageB | 灰度图像或图像掩码 |
| ImageC | 彩色图像 |
| ImageI | 索引（颜色表）图像 |
从PDF 1.4开始，此功能被认为是过时的。为了与现有的符合规范的阅读器兼容，符合规范的编写器应继续指定程序集（最好是表314中列出的所有程序集，除非已知需要更少的程序集）。但是，符合规范的阅读器不应依赖于此信息的正确性。
The PDF operators used in content streams are grouped into categories of related operators called procedure sets (see Table 314). Each procedure set corresponds to a named resource containing the implementations of the operators in that procedure set. The ProcSet entry in a content stream’s resource dictionary (see 7.8.3, “Resource Dictionaries”) shall hold an array consisting of the names of the procedure sets used in that content stream. These procedure sets shall be used only when the content stream is printed to a PostScript output device. The names identify PostScript procedure sets that shall be sent to the device to interpret the PDF operators in the content stream. Each element of this array shall be one of the predefined names shown in Table 314.
| Name | Category of operators |
|---|---|
| Painting and graphics state | |
| Text | Text |
| ImageB | Grayscale images or image masks |
| ImageC | Colour images |
| ImageI | Indexed (colour-table) images |
Beginning with PDF 1.4, this feature is considered obsolete. For compatibility with existing conforming readers, conforming writers should continue to specify procedure sets (preferably, all of those listed in Table 314 unless it is known that fewer are needed). However, conforming readers should not depend on the correctness of this information.