/phplatex

Inline TeX in PHP pages

Primary LanguagePHPGNU General Public License v2.0GPL-2.0

Renders LaTeX into images by calling LaTeX itself from PHP.

See also http://phplatex.scarfboy.com/ and example use on http://latex.knobs-dials.com/

Requirements

  • PHP (>=4.3.0, as it uses sha1())
  • imagemagick (for convert)
  • ghostscript, and TeX Live (or teTeX), (for latex and dvips)
  • TeX packages: color, amsmath, amsfonts, amssymb, and the extarticle document class. Most are standard. You may need non-ancient versions of some.

Installation

  • Put phplatex.php somewhere from which you can include it

  • Have the requirements installed, and check they are where phplatex.php expects them to be (/usr/bin), or edit it as needed

  • Create subdirecties 'tmp' and 'images' in each directory you will be calling the script from, with write permissions for the effective user, for example mkdir tmp images; chown apache:apache tmp images

  • If you get "convert: not authorized" this is likely due to an 2018 ImageMagick update that disable PDF/PS conversions by default, apparently for security, and you need to tweak its policy.xml to re-enable it.

Use

  • Include the code: include('path/to/phplatex.php');
  • To render some TeX: echo texify("TeX");

Due to PHP parsing, you will need to double all your backslahes, and escape your dollar signs, like \$\\sqrt[3]{2}\$. PHP offers no alternatives to this. Yes, you can selectively get away with not doing it (e.g. if dollar signs aren't followed by text so can't name a variable, like in this example), but it's probably less confusing if you are consistent with this.

For advanced/creadive (ab)use, the function definition is actually:

  • texify(texstring, dpi, r,g,b, br,bg,bb, extraprelude); So, for example:
  • print texify('Times in TeX', 160, 0.2,0.0,0.0, 1.0,1.0,1.0, '\\usepackage{pslatex}');

Maintenance

  • Remove leftovers in the tmp directory at will
  • You can empty the img directory to remove unused images (still-used one will be regenerated)

Features

  • Will cache generated images, based on a hash of the document string. Meaning leaving the texify() calls on your page is cheap as successive runs will not run LaTeX at all.
  • CSS lowering to compensate for descenders, so TeX text used inline in HTML should look halfway decent.
  • Tweakable size. The default (90) is approximately the same size as HTML text. Capped at 300 for memory reasons.
  • Allows inclusion of extra TeX packages, via extraprelude.
  • Allows coloring of page background and default text color (default is black on white, 0.,0.,0. on 1.,1.,1.)
  • Generates PNGs with transparency (note: consider antialiasing to that background)
  • Relies on image trimming (instead of e.g. trusting dvips' bounding box)

Caveats

  • Won't work on safe-mode PHP (common enough on cheap shared hosting)
  • I cannot guarantee this is safe from a security standpoint -- in theory it's mostly fine, but TeX is a full-fledged language. There is no input filter on what TeX is allowed. Know what this means security-wise - USE AT YOUR OWN RISK. In particular, the processes can do everything the effective user (of the apache process) can.
  • Fails on TeX that is more than one page. Should not bother you for most things that are inline. Sometimes-workaround: use \small or \footnotesize and a larger DPI setting. TODO: think about better fixes.
  • Image conversion can fail for very large images (hence the DPI cap)
  • the relative tmp and images directories are a little awkward. But the alternative (having a configurable path, to e.g. share the cache) would involve more thinking of how that is exposed URL-wise

Arguables

  • Uses latex's \nonstopmode, meaning it willbest-guess-fix errors it can, rather than complain and stop. You can get away with some bad TeX
  • On low resolutions, the (default) Computer Modern fonts don't render as nicely as, say, pslatex fonts (Times, Helvatica, Courier), due to thickness and antialiasing. Change fontset to taste.
  • Image generation can take a second per image. You may hit your configured PHP max_execution_time limit a few times before a page with a lot of TeX images is all built and cached.
  • I'm no particular fan of PHP, but this does make it pretty portable.

Just math with fewer requirements

This project was made to get a real TeX environment, to compile arbitrary TeX.

If you care only about formulae on webpages (and not full documents, or precisely the same behaviour as real TeX), you can avoid that heavy depdendency and its security issues, by considering options like like:

  • mathJax

    • takes LaTeX, MathML, and AsciiMath
    • produces HTML+CSS (and experimental SVG), or MathML where browser supports
    • code is pure JS

  • latex.js

You may also care about live editing, like latex.js's, mathurl's, and others

Less interesting: