![]() Like their counterparts in other markup languages, PDF structure elements may have content and attributes. PDF logical structure shares basic features with standard document markup languages such as HTML, SGML, and XML.Ī document’s logical structure shall be expressed as a hierarchy of structure elements, each represented by a dictionary object. The logical structure facilities shall be extensible, allowing conforming writers to choose what structural information to include and how to represent it, while enabling conforming readers to navigate a file without knowing the producer’s structural conventions. Such information may include the organization of the document into chapters and sections or the identification of special elements such as figures, tables, and footnotes. PDF’s logical structure facilities (PDF 1.3) shall provide a mechanism for incorporating structural information about a document’s content into a PDF file. This is where Logical Structure (Section 14.7, ISO 32000-1) comes into play. As-is that's not any help for repurpose of content out to another file format or for Accessibility. So, we have content painted to the PDF page. (Each PDF Page is a Painting - Why PDF "reading order" is irrelevant to accessibility) Then the Header followed by the Footer.īody text is often not painted/drawn in the human expected order.Ī nicely detailed discussion of this is available here: The content is often not placed in the PDF in a natural read order.īody text may be painted/drawn first. Section 14 of ISO 32000-1 expands on each of the rules to provide a detailed discussion.Īn Adobe document ("AcrobatWorkshop_final.pdf") provides useful background. Types.” Likewise, conforming writers can define additional structure attributes using any of the available extension mechanisms. Structure types as long as they also provide a role mapping to the nearest equivalent standard types, as described in 14.7.3, “Structure Conforming writers are free to define additional The types and attributes defined for Tagged PDF are intended to provide a set of standard fallback roles and minimum guaranteed attributes toĮnable conforming readers to perform operations such as those mentioned previously. Standard structure attributes preserve styling information used by the conforming writer in laying out content on the page.Ī Tagged PDF document shall also contain a mark information dictionary (see Table 321) with a value of true for the Marked entry. Structure attributes (14.8.5, “Standard Structure Attributes”).Of structure elements, such as paragraphs, headings, articles, and tables. A set of standard structure types define the meaning Structure types (14.8.4, “Standard Structure Types”).A set of rules for describing the arrangement of structure elements on the page. A basic layout model (14.8.3, “Basic Layout Model”).Actual content shall be distinguished from artifacts of layout and pagination.Ĭontent shall be given in an order related to its appearance on the page, as determined by the conforming writer. Word breaks shall be represented explicitly. Tagged PDF defines a set of rules for representing text in the page content so that characters, words, and text order can be determined reliably.Īll text shall be represented in a form that can be converted to Unicode. Page content (14.8.2, “Tagged PDF and Page Content”).Making content accessible to users with visual impairments (see 14.9, “Accessibility Support”)Ī tagged PDF document shall conform to the following rules:.Conversion to other common file formats (such as HTML, XML, and RTF) with document structure and basic styling information preserved.Processing text for such purposes as searching, indexing, and spell-checking.Automatic reflow of text and associated graphics to fit a page of a different size than was assumed for the original layout.Simple extraction of text and graphics for pasting into other applications.It is intended for use by tools that perform the following types of operations: A conforming writer is not required to produce tagged PDF documents however, if it does, it shall conform to these rules. It defines a set of standard structure types and attributes that allow page content (text, graphics, and images) to be extracted and reused for other purposes.Ī tagged PDF document is one that conforms to the rules described in this sub-clause. Tagged PDF (PDF 1.4) is a stylized use of PDF that builds on the logical structure framework described in 14.7, “Logical Structure.” From ISO 32000-1 (the ISO Standard for PDF).
0 Comments
Leave a Reply. |