LatexModePlugin

This LaTeX Mode TWiki Plugin allows you to include LaTeX mark up commands within a TWiki page. It uses external programs (specifically latex, dvipng, or dvips-and-convert) to generate png images from the mark up. These images are then included in the rendered TWiki page. The first time a particular image is generated, there may be a significant lag in page rendering as the images are generated on the server. Once rendered, the image is saved as an attached file for the page, so subsequent viewings will not require re-renders. When you remove a math expression from a page, its image is deleted.

This plugin expands the functionality provided by the (older) TWiki:Plugins.MathModePlugin.

Syntax Rules

The plugin interprets a number of delimiters to declare LaTeX markup strings. For example, if the LatexModePlugin is successfully installed, the string \int_{-\infty}^\infty e^{-\alpha x^2} dx = \sqrt{\frac{\pi}{\alpha}} will render as an image , when enclosed within the defined delimiters.

Standard Syntax

This plugin has two standard modes:

• in-line, declared by %$ $%. Similar to LaTeX's inline math mode, the math markup is rendered on the same line as other text in the string.
• own-line, declared by %\[ \]% or %MATHMODE{ ... }%. These equations will be rendered with center justification on their own line.

For the majority of users, these commands should be sufficient

Extended Syntax

For those that are well familiar with LaTeX, a multi-line syntax allowing more complicated markup commands can be declared using

%BEGINLATEX%
  \begin{<environment>}
    _latex markup_ 
  \end{<environment>}
%ENDLATEX%

Typically, the declared <environment> will be displaymath, although there is no limitation.

Additional options can be included to modify the rendered result. These include

For example, to declare an equation to be numbered by TWiki (not in the LaTeX image) with a larger font size and in red, use the following syntax:

%BEGINLATEX{label="eq1" density="175" color="red"}%

latex markup

%ENDLATEX%

HTML references to Latex equations with a defined <label> can be generated using %REFLATEX{<label>}%.

Tables, Figures, and back-references

To round out the functionality available in standard LaTeX, the automatic generation of Figure and Table reference links is also available. These are declared using

• %BEGINFIGURE{label="fig:label" caption="this is a figure" span="twocolumn"}% ... %ENDFIGURE%, and
• %BEGINTABLE{label="tbl:label" caption="this is a table" span="twocolumn"}% ... %ENDTABLE%.

These commands will create an HTML table with a numbered caption either above (TABLE) or below (FIGURE) the included text. Back-references to these declared environments can be accessed through %REFLATEX{<label>}%. To keep the counters/back-references seperate for each of the three types of references, use eqn:, fig:, and tbl: as the first four characters in any declared label.

The span option is used only by TWiki:Plugins.GenPDFLatex, giving the ability to use designate the width of a table or figure in two-column styles. (e.g. for Figures, it expands to \begin{figure*} ... \end{figure*}.) The default span is one-column.

Font Color

As of v1.3, one can now directly control the foreground font color in the rendered mathematics. This is achieved through use of the color.sty package in the intermediate latex file.

Latex is able to render colors defined in 3 color spaces: gray, rgb, and cmyk. A limited number of colors are predefined in Latex. These include:

For convenience, the following TWiki colors are pre-defined in the LatexModePlugin

   \definecolor{Red}{rgb}{1,0,0}
   \definecolor{Blue}{rgb}{0,0,1}
   \definecolor{Yellow}{rgb}{1,1,0}
   \definecolor{Orange}{rgb}{1,0.4,0}
   \definecolor{Pink}{rgb}{1,0,1}
   \definecolor{Purple}{rgb}{0.5,0,0.5}
   \definecolor{Teal}{rgb}{0,0.5,0.5}
   \definecolor{Navy}{rgb}{0,0,0.5}
   \definecolor{Aqua}{rgb}{0,1,1}
   \definecolor{Lime}{rgb}{0,1,0}
   \definecolor{Green}{rgb}{0,0.5,0}
   \definecolor{Olive}{rgb}{0.5,0.5,0}
   \definecolor{Maroon}{rgb}{0.5,0,0}
   \definecolor{Brown}{rgb}{0.6,0.4,0.2}
   \definecolor{Black}{gray}{0}
   \definecolor{Gray}{gray}{0.5}
   \definecolor{Silver}{gray}{0.75}
   \definecolor{White}{gray}{1}

To use additional colors, they need to be defined in the Latex preamble, as described in the next section.

Defining the LaTeX preamble

In LaTeX, the preamble is used to customize the latex processing, allowing one to add custom styles and declare new commands.

In TWiki, the preamble can be set as either a web or topic preference variable

   * #Set PREAMBLE = \usepackage{color} \definecolor{Aqua}{rgb}{0,1,1}

or as a multi-line declaration, using the tags:

   %BEGINLATEXPREAMBLE% ... %ENDLATEXPREAMBLE%

One critical difference between the two exists. With the exception of the color declarations above, the TWiki preference setting will override the default settings, and is intended to provide site administrators a central point to set preamble settings globally. In contrast, the tag declaration will add to the preamble defined by either the default settings or the preference setting, allowing TWiki users to amend the preamble.

Examples

This is an example of the rendering possibilities using the LatexModePlugin. The singular value decomposition of a matrix is defined as   (1) where and are both matrices with orthonormal columns, indicates a complex-conjugate transpose, and is a diagonal matrix with singular values along the main diagonal. Eq. (1) is just one of the many matrix decompositions that exists for matrix .

After the plugin has been succesfully installed and configured, this example should render like this:

[Note: the following may or may not be useful...] Both DENSITY and SCALE alter the rendered image size and quality. For example, if one doubles the DENSITY and halves the SCALE, the rendered image resolution will improve but keep the same image size on the rendered page. (Note: DENSITY * SCALE is the same in both cases)

For regular browser viewing, the SCALE parameter sould be set to 1.0. However, one can use these parameters to improve print quality when printing a topic. To do this, increase the DENSITY setting (a value of 300 will give roughly 300dpi) and then set the SCALE setting below 1.0.

Plugin Settings

Plugin settings are stored as preferences variables. To reference these plugin settings write %<plugin>_<setting>%, i.e. %LATEXMODEPLUGIN_SHORTDESCRIPTION%

• One line description, as shown in the TextFormattingRules topic:
  • Set SHORTDESCRIPTION = Enables LaTeX markup (mathematics and more) in TWiki topics

• Debug plugin: (See output in data/debug.txt)
  • Set DEBUG = 0

• Set the dots-per-inch default density level for the rendered images (116 is suggested for 11pt browser fonts.)
  • Set DENSITY = 116

• Set the gamma correction for the rendered images. This controls how dark the rendered text appears
  • Set GAMMA = 0.6

• Set the scaling for the image size. Typically, set to '1'.
  • Set SCALE = 1.0

• Uncomment the following to define a site-wide custom color, DarkBlue.
  • #Set PREAMBLE = \usepackage{color} \definecolor{DarkBlue}{rgb}{0,0.1,0.43}

• In addition, the following parameters are available at the topic level, EQN, FIG, TBL, to override the counter reset. (i.e. if    * Set EQN = 3 is declared in a topic, the first labeled equation will be given the number 4).

Plugin Installation Instructions

First, confirm that the external software needed by the plugin is installed on the TWiki server. This includes:

• The Digest::MD5 and Image::Info perl modules.
• A working LaTeX implementation (tetex and MikTeX are two popular choices)
• dvipng, a fast dvi to png converter
• the Ghostscript package
• the 'convert' executable from either ImageMagick or GraphicsMagick

Rendering can be performed by either (dvipng) or (dvips and convert). dvipng is significantly faster. However, the tweakinline processing currently (v 2.5) uses convert. Installation requires at least one, and best results will be seen if all are installed.

Second,

• Download the LatexModePlugin.zip file from the Plugin web
• Unzip ZIP file in your twiki installation directory. Content:

  File:	Description:
  lib/TWiki/Plugins/LatexModePlugin.pm	Plugin Perl module
  data/TWiki/LatexModePlugin.txt	Plugin topic and documentation
  data/TWiki/LatexIntro.txt	a basic description of LaTeX markup conventions
  data/TWiki/LatexSymbolList.txt	Comprehensive list of available LaTeX symbols
  pub/TWiki/LatexModePlugin/expl-v1.4.png	example image of rendered latex

Finally, customize the installation specific variables.

• Set the local paths of latex, dvips and convert. This can be done by adding the following lines to lib/LocalSite.cfg or lib/TWiki.cfg.
  • $TWiki::cfg{Plugins}{LatexModePlugin}{latex} = '/usr/bin/latex';
  • $TWiki::cfg{Plugins}{LatexModePlugin}{dvips} = '/usr/bin/dvips';
  • $TWiki::cfg{Plugins}{LatexModePlugin}{dvipng} = '/usr/bin/dvipng';
  • $TWiki::cfg{Plugins}{LatexModePlugin}{convert} = '/usr/X11R6/bin/convert';
• Modify the following if needed.
  (These variables were introduced in version 2.4)
  • $TWiki::cfg{Plugins}{LatexModePlugin}{donotrenderlist}
    declare a comma-separated list of LaTeX commands that will not be rendered.
    Default = 'input,include'.
  • $TWiki::cfg{Plugins}{LatexModePlugin}{tweakinline}
    Turned off by default, setting this boolean variable to 1 will enable more complex in-line rendering. See the TWiki:Plugins.LatexModePluginDev topic for more details.

More Details

Version control is not specifically used for the image files. Because the images are generated from the raw text, the topic history includes all the versions of the markup for the expressions, and can be re-rendered when you view a different version.

This plugin is an enhanced version of the TWiki:Plugins.MathModePlugin created by TWiki:Main.GraemeLufkin. There are a number of significant differences:

• dvipng or latex-dvips-convert is used in place of latex2html, consequently
  • hash table mismatching between twiki and images generated by latex2html is eliminated, which was a source of many problems in the TWiki:Plugins.MathModePlugin.
  • greater flexibility in markup rendering is available.
  • the rendering is done image-by-image, so the cost of total page rendering time should be linear. (that is, ten images will take ten times as long to render as one image.)
• multi-line latex markup is now possible. Consequently, this now means that a <nop> must be included to disable rendering in documentation, as opposed to spliting the math markup over multiple lines as before.
• equations can be numbered, with automatic cross-links available
• if errors occur during the latex markup processing, they are reported during the editing preview screen, but not during the standard view. The motivation for this is that, in general, authors care about the error but readers do not.
• as of version 2.5, one can force the recreation of all latex images in a topic. To do this, add the following text (similar to raw text rendering) to the end of the URL: ?latex=rerender. E.g. changing http://localhost/twiki/bin/view/TWiki/LatexModePlugin to http://localhost/twiki/bin/view/TWiki/LatexModePlugin?latex=rerender will force all of the images to be redrawn.

Plugin Info

Plugin Author:	TWiki:Main.ScottHoge
Plugin Version:	14 Mar 2006 (v 2.5)
Change History:
14 Feb 2006 (v 2.5)	added rerender hook, fixed '> in alt field' bug.
21 Feb 2006 (v 2.4)	introduced donotrenderlist to patch a critical security hole. Bug fixes include: disabling WikiWord link rendering in alt fields of img tags; improved in-line rendering alignment available;
1 Feb 2006 (v 2.3)	minor bug fixes: $pathSep changes, now uses &TWiki::Func::extractParameters()
11 Nov 2005 (v 2.2)	more mods for TWiki:Plugins.GenPDFLatexAddOn: protect newlines, moved float handler, moved float label checker
15 Oct 2005 (v 2.1)	minor modifications for TWiki:Plugins.GenPDFLatexAddOn support
unreleased (v 2.0)	Major rewrite for Dakar
30 Sep 2005 (v 1.41)	relaxed the scrubing a little bit... previous version caused problems with REFLATEX
29 Sep 2005 (v 1.4)	more robust scrubing of convert input parameters. errors on save now reported.
5 Sep 2005 (v 1.3)	added image scale parameter, color rendering, and preamble hooks
22 Aug 2005 (v 1.2)	Forked from the TWiki:Plugins.MathModePlugin by TWiki:Main.GraemeLufkin
TWiki Dependency:	$TWiki::Plugins::VERSION 1.025
CPAN Dependencies:	CPAN:Digest::MD5, CPAN:File::Basename, CPAN:Image::Info
Other Dependencies:	A working installation of latex. A working installation of convert or dvipng.
Perl Version:	5.8.0
License:	GPL (GNU General Public License)
TWiki:Plugins/Benchmark:	GoodStyle 100%, FormattedSearch 100%, LatexModePlugin 100%
Plugin Home:	http://TWiki.org/cgi-bin/view/Plugins/LatexModePlugin
Feedback:	http://TWiki.org/cgi-bin/view/Plugins/LatexModePluginDev
Appraisal:	http://TWiki.org/cgi-bin/view/Plugins/LatexModePluginAppraisal

This plugin was created and tested on the 02 Sep 2004 version of TWiki, using ImageMagick v5.5.7, EPS GhostScript v7.05, and tetex v2.02. It has been reported to work (Thanks Jos!) using ImageMagick 6.2.3, tetex 3.0 and ghostscript 8.51 as well.

Related Topics: TWikiPreferences, TWikiPlugins, TWiki:Plugins.MathModePlugin