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Finished structure tree documentation

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John Whitington 2024-09-24 13:38:56 +01:00
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@ -5214,7 +5214,7 @@ There are two types of tag we can add manually. One kind is used to tag individu
\noindent\small\verb! -et -end-tag -auto-tags -mtrans "0 -100" -font-size 20 -leading 25!\\ \noindent\small\verb! -et -end-tag -auto-tags -mtrans "0 -100" -font-size 20 -leading 25!\\
\noindent\small\verb! -bt -paras "L200pt=This is the first paragraph, which spreads over!\\ \noindent\small\verb! -bt -paras "L200pt=This is the first paragraph, which spreads over!\\
\noindent\small\verb!more than one line\nHere is the second, which also has multiple lines..."!\\ \noindent\small\verb!more than one line\nHere is the second, which also has multiple lines..."!\\
\noindent\small\verb! -et AND -o out.pdf! \noindent\small\verb! -et -o out.pdf!
\end{framed} \end{framed}
\noindent We turned off auto-tagging with \texttt{-no-auto-tag}, then used \texttt{-tag H1} and \texttt{-end-tag} to tag the heading. Then we turned auto-tagging back on with \texttt{-auto-tag}. Here is the result, visually: \noindent We turned off auto-tagging with \texttt{-no-auto-tag}, then used \texttt{-tag H1} and \texttt{-end-tag} to tag the heading. Then we turned auto-tagging back on with \texttt{-auto-tag}. Here is the result, visually:
@ -5232,21 +5232,40 @@ There are two types of tag we can add manually. One kind is used to tag individu
└── /P (1) └── /P (1)
\end{verbatim} \end{verbatim}
\noindent Content tagging is flat - every part of the content of a page is part of only one \texttt{-tag}. The logical structure of a document, however, is a tree structure -- sections contain paragraphs, and so on. To build the logical structure tree, we add structure tags using \texttt{-stag} / \texttt{-end-stag} pairs which, of course, may be nested. For example, let's put our H1, and P sections in a Section structure tag:
\noindent\verb!-stag! Begin structure tree branch\\ \begin{framed}
\noindent\verb!-end-stag! End structure tree branch\\ \noindent\small\verb!cpdf -create-pdf AND -draw-struct-tree -draw -mtrans "50 700" !\\
\noindent\small\verb! -font-size 40 -no-auto-tags -stag Section -tag H1 -bt!\\
\noindent\small\verb! -text "This is the heading" -et -end-tag -auto-tags -mtrans "0 -100" !\\
\noindent\small\verb! -font-size 20 -leading 25 -bt -paras "L200pt=This is the first parag!\\
\noindent\small\verb!raph, which spreads over more than one line\nHere is the second, which al!\\
\noindent\small\verb!so has multiple lines..." -et -end-stag -o out.pdf!
\end{framed}
(describe how structure tags are different). Sections example. Top-level /Document example. \noindent Here is the structure tree:
\noindent\verb!-artifact! Begin manual artifact\\ \begin{verbatim}
\noindent\verb!-end-artifact! End manual artifact\\ /StructTreeRoot
\noindent\verb!-no-auto-artifacts! Prevent automatic addition of artifacts during postprocessing\\ └──/Section (1)
├── /H1 (1)
├── /P (1)
└── /P (1)
\end{verbatim}
(talk about artifacting) \noindent Some PDF standards require that everything not marked as content (e.g paragraph, figure) etc. is marked as a an artifact. For example, a background image which is the same on every page, or a page border. This tells PDF processors that it is not logical content.
\noindent\verb!-namespace! Set the namespace for future branches of the tree\\ By default, Cpdf with \texttt{-draw-struct-tree} will mark anything not automatically or manually tagged as content as an artifact. Should you wish to disable this, you may use \texttt{-no-auto-artifacts}. Whether or not you use \texttt{-no-auto-artifacts}, you may use \texttt{-artifact} / \texttt{end-artifact} pairs to mark artifacts manually. For example:
(namespaces, with particular reference to PDF/UA2) \begin{framed}
\noindent\small\verb!cpdf -create-pdf AND -draw-struct-tree -draw -no-auto-artifacts!\\
\noindent\small\verb! -artifact -mtrans "50 700" -end-artifact -bt -text "Hello" -et!\\
\noindent\small\verb! -o out.pdf!
\end{framed}
\noindent Here we manually tagged the \texttt{-mtrans} as being an artifact. The text section was automatically tagged as a paragraph, and so all content has been tagged or marked as an artifact.
Some tags require a namespace other than the default. You can set the namespace with \texttt{-namespace}, which affects all future tags until reset. Two namespace abbreviations are available: \texttt{PDF} for the default \texttt{http://iso.org/pdf/ssn} namespace and \texttt{PDF2} for the PDF 2.0 namespace \texttt{http://iso.org/pdf2/ssn}.
\fi%End htlatex hack \fi%End htlatex hack