Guide to LaTeX (4th Edition) (Tools and Techniques

476 Appendix E. L AT E X and World Wide Web
E.1 Converting to HTML
E.1.1 The L AT E X2HTML program
The L AT E X2HTML translator, written by Nikos Drakos with additions by a
large number of contributors, is a comprehensive Perl script that converts
a L AT E X source file into HTML with the help of several other programs,
notably L AT E X itself, dvips, Ghostscript, and the netpbm library of graphics
utilities.
When L AT E X2HTML processes a L AT E X file, it creates a new subdirectory
with the same name as that file, to which it writes the resulting HTML
output and any generated images as .gif files. The program interprets
the L AT E X input text in the same way as L AT E X itself does, but instead of
producing typesetting instructions in the .dvi file, it writes appropriate
HTML code to an .html file. For example, \section{Introduction} is
interpreted as Introduction for the output.
This means that L AT E X2HTML is essentially duplicating the L AT E X processing,
an enormous undertaking. Since the document classes contain
varying commands or have common ones behaving differently, there must
be Perl scripts for each one (article.perl, and so on) to program these
commands properly. Additional packages loaded with \usepackage can
also define new commands, or alter the functionality of existing ones;
the translator must be informed about these by means of corresponding
Perl scripts. For example, the natbib package described in Section 9.3.4
defines citation commands \citet and \citep, which need to be made
available to L AT E X2HTML in a file natbib.perl. Most of the tools packages
of Section B.5.4 are included as Perl scripts, as are many other popular
contributed packages. In other words, the entire L AT E X2HTML installation
must mirror the L AT E X one.
This process is somewhat simplified by the fact that both formats
are markup languages written in pure typewriter text. However, this
similarity soon reaches its limits with the many L AT E X features not available
in HTML, such as complex math, included figures, cross-referencing. In
the other direction, HTML exhibits hyperlinks, both internally and to
external documents, something not provided by normal L AT E X.
L AT E X2HTML attempts to reproduce math with the limited HTML possibilities,
but failing that, formulas are handled the same as figures and
other environments that cannot be directly rendered: they are converted
to GIF image files along the route.tex →.dvi →.ps →.pbm →.gif, which
are then included in the HTML file as in-line images.
Cross-references and citations are automatically provided with hyperlinks
to their targets; the keyword index also links back to the text. Other
features of HTML can be included by means of special commands defined
in the html.sty package. For example:
• explicit hyperlinks, internal and external