BB Code Enhancements - vLaTeX - Math parsing with LaTeX

vLaTeX allows your users to include mathematical equations written in LaTeX into their posts, rendered in high quality graphic files (either png or gif). Such ability is instrumental in scientific or educational oriented forums. When I started in vb two years ago, there ware a number of solutions available, but none of them suited my needs completely, so I developed my own integration between (a modified version of) Benjamin Zeiss' LatexRender and vBulletin. With the new vBulletin 4.0, I decided to improve some of the features of this product, and to release it with the hope that it turns out to be useful to any of you.


What is LaTeX?

LaTeX is a set of macros for the TeX typesetting system. It is the defacto standard of communication within the scientific and mathematical community. It works pretty much like a programing language: you write a text source file, and the latex executable compiles it in a DeVice Independent file (DVI), which can be later converted to the desired format (postscript, pdf, etc.).

This mod (thanks to a modified version of the LatexRender class) does all this work in the background. It takes the formula code, inserts it in a source file, compiles it and converts the output in a high quality image file (png or gif, depends on your settings) to show in the post.


Requirements

This mod relies on your server having available the following external programs. They are pretty standard in most Linux distributions, so hosts can install them easily (if they want to, some don't). Please, check your server meets this requirements (or ask your host to install the programs) before trying to use vLaTeX:

- latex: the LaTeX compiler. Check the TeX live distribution (http://www.tug.org/texlive/).

- dvips: converts the DVI file to PS. Usually included in all latex distributions.

- convert: as it name suggests, converts between a large number of graphic files. Belongs to the ImageMagick package. Needs ghostscript.

- identify: among other things, measures the size of image files. Also belongs to ImageMagick

- Ghostscript: PostScript and PDF language interpreter and previewer. Is called by convert in order to handle ps files.


Features

Creates a new BBcode, usually [TEX] (thought the tag name is configurable via the admin cp), which contents are processed thought LaTeX to generate image files. There are four calling modes:

- [TEX]E= mc^2[/TEX] in-line mode. The image is included in the middle of the text, without line breaks. It tries to adjust the baseline of the formula by adjusting the vertical-align CSS property; the results aren't always perfect, but it does its best.

- [TEX=null]E = m c^2[/TEX] displayed mode: The formula is displayed (usually centered) between two paragraphs.

- [TEX=*]E = m c^2[/TEX] auto-numbering mode: The formula is displayed (usually centered), and numbered.
NOTE: The auto-numbering depends on the CSS counter system, so some old browsers (most notably ie 7 and older) will show these equations untagged, like [TEX=null]. Don't blame me, blame non-standard compilant browsers.

- [TEX=tag]E = m c^2[/TEX] displayed with tag: The formula is displayed (usually centered) between two paragraphs, and tagged with the specific tag.

In the last two modes, the tags are displayed at the right (left if you use RTL) between brackets, in a (configurable) color.

The formulas are compiled by creating a small tex file and running the native LaTeX program throughout it. You can choose to wrap the formula with the standard dollar ($ ... $), the align or gather amsTeX environments. The standard dollar is recommended since the baseline hack works better with it, but the gather environment allows to create multiline equations using the \\ separator.

This mod also introduces a second BBcode, [EQREF]tag[/EQREF], which outputs (tag), with the same style of the equation tags. It's useful to let users make reference their formulas.

A double click on the image of a generated image will open a pop-up displaying the LaTeX source code used to generate the formula.

Menu with Common used LaTeX commands can be shown below the advanced mode editor. The admin can customize the commands of the menu thought the admin control panel.


Admin features

Image files are cached, so every unique formula is only processed once.

Fully configurable via Style Variables and templates. It is also fully phrased.

It doesn't change any vb default template, so upgrading should be easy.

Includes a list of blacklisted latex commands for security (configurable in the admin cp).

The admin can customize the preamble of the latex file in the admin cp. This is useful to define new commands that your community uses often, or to include packages.

Error messages can be customized in the phrase system.

Memory usage of ImageMagick commands (convert and identify) can be limited in the admin control panel.


Installation / Upgrade

1.- Unzip the mod files.

2.- Upload the vLaTeX directory to your forum root. The generated folder structure should look like this:

vLaTeX/
vLaTeX/index.htm
vLaTeX/class_vlatex.php
vLaTeX/functions_vlatex.php
vLaTeX/vlatex.js
vLaTeX/pics/
vLaTeX/pics/index.htm
vLaTeX/temp/
vLaTeX/temp/index.htm

3.- Change the permissions of the pics and temp folders so the web server can write on them.

4.- Import the product XML in your admin control panel. If you're upgrading, set "Allow Overwrite" to yes.

5.- Go to Admin CP > Settings > Options > vLaTeX - Math Parsing

6.- Make sure the path to latex, dvips, convert and identify executables is correct. Those settings default to the most common values in most linux distributions, but every host is a different world.
If you have shell access, you can check the location of the executables with the following commands:
which latex
which dvips
which convert
which identify

7.- Make sure the path to the Images and Temporal directory are correct. You can change them if you don't like the default value, but the directories must exist and the server must have permissions to write on them.
For extra safety, you could move the temp folder out of the public accessible directory three, thought it should not be needed, since files are deleted in matter of milliseconds.

8.- Set the rest of options as you wish.

9.- Test the product in some posts.

10.- If you wish to add a button in the advanced editor tool-bar for this mod, you can add it using the admin cp section Custom BB Codes (write anything you want in Replacement, this mod will overwrite it). You can use any tex icon, for instance http://www.iconfinder.com/icondetails/3780/16/tex_icon


Error messages

The LaTeX parsing can fail for a number of reasons. In such case, an error message is displayed instead of the formula. Here's a list of all possible error messages and their meaning:

- "Image too big {1}, max {2}x{3}", The resulting image is bigger than the allowed dimensions.

- "Blacklisted command", The user attempted to compile a formula with a forbidden command.

- "Can't move image", Image formula could be created, but I could not be moved to the destination folder. Check that the directory exists and has write permissions.

- "Convert failed", Formula could be compiled, but could not be converted to png/gif. Check the convert program path.

- "Compile failed", The formula could not be compiled. Check that the temporal directory has write permissions and that the latex path is correct.

- "Code too long, max. {1} characters", The formula code was too long. The maximum length can be configured in the admincp.

- "Formula not found", The compilation and convert process appeared to not raise any error, but the image was not found on the destination folder. Check for permissions in the destination folder and/or IO errors.

- "Pictures directory unwritable", The destination folder does not exist, or has no write permissions.

- "Temp. dir unwritable", The temporal folder does not exist, or has no write permissions.

- "Unknown error", Any other error condition.


Disclaimer

This mod is in beta phase, if you find bugs, please tell me how to reproduce them so I can improve it. It is distributed as is, with the hope that it is useful for someone, but without any warranty. Nor will I accept any responsibility or liability if it doesn't work as expected, or even if it breaks something.
This mod is mainly developed for personal usage. I will listen to good ideas, but I can't guaranty that I will be implemented requested features.


License

This mod is distributed under the LGPL.(http://www.gnu.org/copyleft/lesser.html). As is, you can freely distribute it or any derivative work provided that: 1) you acknowledge the work of the previous coders (like myself and Zeiss), 2) you release it under the same license (or GPL).



Acknowledgments

This mod (in particular, the class_vlatex.php file) is strongly based on the LatexRender class by Benjamin Zeiss (http://www.mayer.dial.pipex.com/tex.htm).

The baseline hack by the work of Maarten Sneep (http://mactextoolbox.sourceforge.net.../baseline.html).


Compatibility

The last version of this mod (0.5.1) requires vb4.2.0 or higher. It should work on previous CKEditor versions, but it was not tested.

If you wish to use it in a pre-CKEditor vb installation, you can use the previous vLaTeX version (0.4.1). If you want to use it in an older vb4.0.x release, you can download version 0.3 (which is compatible with vb4.0.1 or higher). Take into account that old versions of this hack have less features and might have some issues fixed in later versions.

Support will be given only for the last version of this mod.



History

2009 / 12 / 19 - First (beta) release

2009 / 12 / 20 - version 0.2
Fixed baseline problem of in-line formulas in CMS articles.
Improved error handling.
Included Spanish translation

2010 / 1 / 24 - version 0.3 (requires vb4.0.1)
Fixed extra space after in-line equations.
Won't break down if vb's CSS is stored as files.
New pop-up showing the formula source code upon double-click.

2010 / 7 / 23 - version 0.4 (requires vb4.0.4)
Improved support for CSS stored as files.
Fixed bug of js file not being loaded on certain servers.
Menu with common LaTeX commands under vb's advanced editors.
Equations will no longer be break by preview in blogs or CMS articles.

2010 / 4 / 24 - version 0.4.1 (requires vb4.0.4)
Improved compatibility of the Common Commands quick-menu with IE browser.

2012 / 12 / 07 - version 0.5.1 (requires vb4.2.0)
CKEditor support.
Memory limit for imagemagick commands.
Code pop-up now can overflow postbit boundary.

2012 / 12 / 17 - version 0.5.2 (requires vb4.2.0)
Introduced Formula Wrapper option.

[apokphp]

I don't know if my server (which is shared) has the necessary requirements. I assume not, since when I don't see all the icons for the formulas (just text instead) and when I try to post a tex bbcode, I get [LaTeX ERROR: Compile failed] .

Is that what this message means?

[Pod]

Originally Posted by apokphp

I don't know if my server (which is shared) has the necessary requirements. I assume not, since when I don't see all the icons for the formulas (just text instead) and when I try to post a tex bbcode, I get [LaTeX ERROR: Compile failed] .

Is that what this message means?

That most likely means that some of the external programs need to compile the latex files generated by the mod are not in their correct location (you can change where the mod looks for them in the admincp), or are not installed at all. If you have shell access to your host, issue the following commands to know the correct path:

which latex
which dvips
which identify
which convert

If some of this programs are not installed, ask your host to install them. Some shared hostings will be willing to install them for you, some others won't... I only can say good luck. If they have concerns about overloading the server, tell them that this mod caches the formulas, so they are only parsed the first time they are entered.

[apokphp]

nvm. Hostgator (my host) says that because this is a shared server, they cannot install latex and dvips (the others are already installed). They said I'd have to move to a dedicated server to have these 2 installed.

When I was on 3.8.x, I used the Latex plugin, and it didn't have such server requirements. Are you the same author of that plugin?

[Pod]

Originally Posted by apokphp

nvm. Hostgator (my host) says that because this is a shared server, they cannot install latex and dvips (the others are already installed). They said I'd have to move to a dedicated server to have these 2 installed.

When I was on 3.8.x, I used the Latex plugin, and it didn't have such server requirements. Are you the same author of that plugin?

Bad luck. Other hosts have different policies regarding the installation of this tiny programs (I know of shared hosts that run this mod without problems in medium-size boards).

I never released any latex product for 3.8.

You can try to use mimeTeX, which produces a bit poorer equations but has less requirements, you only need to be able to run a cgi (and don't even need a mod, only configure the proper custom bbcode).

[emath]

hey, ive got all necessary programs (latex, dvips , Ghostscript , convert , identify) and all set to the right path in admin cp.

although , i still get this :

[LaTeX ERROR: Compile failed]

i am using vb.4.0.8

any ideas?

[Pod]

Originally Posted by imiviortal

hey, ive got all necessary programs (latex, dvips , Ghostscript , convert , identify) and all set to the right path in admin cp.

although , i still get this :



i am using vb.4.0.8

any ideas?

That error appears if it cannot call the latex executable. Make sure that the full path written in the admincp is correct (in a console, write ls [path], it should show the latex file). If the path is correct, it might be some configuration in php that doesn't give you permission to execute external programs thought the php exec command.

You can try to take a look at the error file in your server to see what was the problem.

[emath]

latex directory is right.

where can i find the "error file"

in addition, what is the :

Document class
Class of the temporal latex file. The compiler should have access to the corresponding .cls file.

where can i see where is the .cls file ?

[Pod]

Originally Posted by imiviortal

latex directory is right.

Not only the directory, but the path to the executable.

Also, remember that this is the path in the file system of your server, not your home computer.

Originally Posted by imiviortal

where can i find the "error file"

Depends on your hosting. If you have cpanel, you can probably see it there.

Originally Posted by imiviortal

in addition, what is the :

Document class
Class of the temporal latex file. The compiler should have access to the corresponding .cls file.

where can i see where is the .cls file ?

You don't need the full path here, just the name of the class. You are probably safe leaving the default value (article).

[emath]

what is the path to the executable ? i have only shell access.

Depends on your hosting. If you have cpanel, you can probably see it there.

i have directAdmin .. u know where i can find it there ?

[Pod]

Originally Posted by imiviortal

what is the path to the executable ? i have only shell access.

Write "which latex". It will tell you the path.

Originally Posted by imiviortal

i have directAdmin .. u know where i can find it there ?

According to directAdmin live demo, in "Site Summary / Statistics / Logs"