knobs-dials / phplatex

Inline TeX in PHP pages

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" when using it, this is likely due to an 2018 ImageMagick update that disabled 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 and so can't name a variable, but it's probably less confusing if you are consistent with this.

For advanced/creative (ab)users, 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. This means leaving texify() on your page is cheap, as later calls will not run LaTeX at all.
• TeX text used inline in HTML is lowered somewhat (via CSS) when it contains characters that descend below the average.
• Tweakable size. The default (90) is approximately the same size as typical page 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, which is common enough on cheap oldschool shared hosting (though it was removed in PHP5.3)
• 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, because that wouldn't even work. 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 TeX will best-guess-fix errors it can, rather than complain and stop. You can get away with some bad TeX and never know it.
• 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.

When to use something else: 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 don't care about the precise behaviour of compiled TeX, then you can get 95% of the way there, get better indeability and copyability for simple things, and/or avoid a heavy depdendency and its security issues, by considering options such as:

• mathJax

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

• latex.js

  • takes TeX
  • produces HTML and SVG
  • code is pure JS
  • seems to do a little more than just math

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

If using mediawiki: the The mediawiki math extension delivers MathML where supported, and falls back to SVG and PNG via mathoid. This only takes its own TeX dialect, texvc, which seems to be safer restricted set of commands, run through a validator.

Less interesting but worth mentioning:

• embedded MathML / element

  • has been standardized for a while, but only a few browsers allow direct use in webpages
  • useful as one rendering option among others

• ASCIIMathML.js

  • takes AsciiMath, makes MathML
  • useful as a component, integrated into mathJax

• jsMath

  • takes LaTeX, MathML (XML based), and asciimath
  • produces HTML+CSS
  • code is pure JS
  • succeeded by mathJax

• components such as iTeX for TeX to MathML, svgmath for MathML to SVG

  • useful for projects but not end users directly