Mathematical

Quickly convert math equations into beautiful SVGs (or PNGs/MathML).

Installation

Add this line to your application's Gemfile:

gem 'mathematical'

And then execute:

$ bundle

Or install it yourself as:

$ gem install mathematical

Note: you'll probably need to run script/bootstrap to fetch all the necessary dependencies.

Usage

The simplest way to do this is

require 'mathematical'

Mathematical.new.render(string_with_math)

string_with_math should just be a string of TeX math. The default delimiters are $..$ for inline and $$..$$ for display. These can be changed by options--see below.

The output will be a hash, with keys that depend on the format you want:

• If you asked for an SVG, you'll get:
  • :width: the width of the resulting image
  • :height: the height of the resulting image
  • :data: the actual string of SVG
• If you asked for a PNG, you'll get:
  • :width: the width of the resulting image
  • :height: the height of the resulting image
  • :data: the PNG data
• If you asked for MathML, you'll get:
  • :data: the MathML data
• If you pass in invalid TeX, you'll get:
  • :data: the original invalid TeX
  • :exception: the error class (with message)

Note: If you pass in invalid TeX, an error is not raised, but a message is printed to STDERR. It is the caller's responsibility to check for :exception and act on it.

render just converts a single equation. There are several other methods you can use:

• filter: Given a string with a mix of TeX math and non-math elements, this returns a single string containing just the converted math elements.
• text_filter: Given a string with a mix of TeX math and non-math elements, this converts all the math and leaves the rest of the string unmodified.
• strict_filter: Given a string with a mix of TeX math and non-math elements, this converts all the math and leaves the rest of the string unmodified. HTML tags are removed completely.

Array of equations

Rather than just a string, you can also provide an array of math inputs:

inputs = []
inputs << '$\pi$'
inputs << '$not__thisisnotreal$'
inputs << '$\alpha$'

Mathematical.new.render(inputs)

This returns an array of hashes, rendering the indices. For example, for the above, you will receive the following output:

[ {:data => "...", :width => ... }, { :data => '$not__thisisnotreal$', :exception => "...", {:data => "...", :width => ... }]

That is, while the first and last elements are valid TeX math, the middle one is not, so the same string is returned. As with single strings, the error message is printed to STDERR, but not raised.

Options

Mathematical.new takes an optional hash to define a few options:

Name	Description	Default
:ppi	A double determining the pixels per inch of the resulting SVG	72.0
:zoom	A double determining the zoom level of the resulting SVG	1.0
:base64	A boolean determining whether Mathematical's output should be a base64-encoded SVG string	false
:maxsize	A numeral indicating the MAXSIZE the output string can be.	unsigned long
:format	A symbol indicating whether you want an :svg, :png, or :mathml output.	:svg
:delimiter	A symbol indicating whether you want an :dollar for inline ($..$), :double for display ($$..$$), :parens for inline (\(..\)), or :brackets for display ([..\]). You can also pass in an array of symbols to have multiple delimiters considered.	[:dollar, :double]

Pass these in like this:

options = { :ppi => 200.0, :zoom => 5.0, :base64 => true }
renderer = Mathematical.new(options)
renderer.render('$a \ne b$')

Supported commands and symbols

Check out SUPPORTED.md on the mtex2MML website.

Note: This library makes a few assumptions about the strings that you pass in. It assumes that $..$ is inline math and $$..$$ is display math.

Building

Before building this gem, you must install the following libraries:

• GNU make
• glib-2.0
• gdk-pixbuf-2.0
• xml2
• cairo
• pango
• Dependencies for mtex2MML

After cloning the repo, you can fetch dependencies and run the library by typing:

script/bootstrap
bundle exec rake compile

If there were no errors, you're done! Otherwise, make sure to follow the dependency instructions.

Fonts and special notices for Mac OS X

Install the fonts with:

cd ~/Library/Fonts
curl -LO http://mirrors.ctan.org/fonts/cm/ps-type1/bakoma/ttf/cmex10.ttf \
     -LO http://mirrors.ctan.org/fonts/cm/ps-type1/bakoma/ttf/cmmi10.ttf \
     -LO http://mirrors.ctan.org/fonts/cm/ps-type1/bakoma/ttf/cmr10.ttf \
     -LO http://mirrors.ctan.org/fonts/cm/ps-type1/bakoma/ttf/cmsy10.ttf \
     -LO http://mirrors.ctan.org/fonts/cm/ps-type1/bakoma/ttf/esint10.ttf \
     -LO http://mirrors.ctan.org/fonts/cm/ps-type1/bakoma/ttf/eufm10.ttf \
     -LO http://mirrors.ctan.org/fonts/cm/ps-type1/bakoma/ttf/msam10.ttf \
     -LO http://mirrors.ctan.org/fonts/cm/ps-type1/bakoma/ttf/msbm10.ttf

Note: There's a severe issue with Cairo@1.14.2 and Yosemite. Don't use this version of Cairo. Instead, use the older 1.12.16 version, which you can install with:

brew install https://raw.githubusercontent.com/Homebrew/homebrew/26d5775494b3535820c48442c23af44f72974880/Library/Formula/cairo.rb

You may also need to install the XQuartz tooling, as this is required by Cairo.

Benchmark

Run benchmarks with bundle exec rake benchmark:

Benchmarking....
Count: 3868 equations
Iterations: 1
                                               user     system      total        real
Rendering...                               3.280000   0.070000   3.350000 (  4.324458)

History

There are a smattering of libraries written in various languages to convert math into a variety of formats. But there needs to be a sane way to show math equations in the browser. With browser support for MathML under attack, it's unfortunately not a sustainable solution. A PNG or SVG representation of the equation is the safest way to go.

Most advice suggests using MathJax. While extremely popular I dislike the "stuttering" effect caused by pages loading math. JavaScript shouldn't be used in situations where server-rendering is a possibility, in my opinion.

To that end, I obsessed over the problem of server-side math rendering for over a week. Here was my journey:

• I started out with blahtexml, which takes TeX equations and converts them to PNG. This wasn't a bad idea, but it took too long; for twelve equations, it took eight seconds. It was slow because it shelled out to LaTeX, then dvipng.

  In fact, as I discovered, most projects on the 'Net shell out to LaTeX, then something else, which makes performance absolutely horrid. I had to find something better, with preferably no dependency on LaTeX.

• mimetex was my next attempt. It looked great: a pure C implementation that turned TeX equations into a rasterized representation, and then into a PNG. The speed was there, but the output image was pretty jagged. I tweaked the program to output BMPs, and tried to sharpen those with potrace, but the results were less then pleasant. The "update" to mimetex is mathtex, but it, too, depends on LaTeX and dvipng binaries to produce images.

• pmml2svg had potential. It's a set of XSLT stylesheets to convert MathML to SVG. Unfortunately, it relies on XSLT 2.0, of which there are no Ruby bindings (at the time of this writing, April '14). It had to rely on Saxon and Java.

• tth converts TeX to HTML, but the output is aesthetically unpleasing, so I passed.

• Wikipedia uses texvc, which is written in OCaml, a language I am utterly unfamiliar with. In any event, I could not get the code to compile on my machine.

• It took me forever to finally compile gtkmathview, and when it did, I got a bunch of SVG images with screwed up fonts.

• dvisvgm worked well, but still depended on two external binaries (LaTeX to convert the text to dvi, and dvisvgm to turn it into SVG)

• At one point, I began to try and convert the MathJax code to Ruby to figure out how it accomplished its toSVG methods. The MathJax codebase, while written by geniuses, is incomprehensible, due in part to JavaScript's inability to possess a coherent structure.

• Near the end of my wits, I mimicked the behavior of mathrender2, which uses PhantomJS to embed MathJax onto a fake HTML page. This produced exactly what I needed: a bunch of accurate SVG files with no intermediate binaries. It was, unfortunately, a bit slow: for an arbitrary composition of 880 equations, it took about eight seconds to complete. Could I do better?

• I came across Lasem, which met every need. It has no external binary dependencies (only library packages), can convert directly to SVG, and it's fast. The same arbitrary 880 equations were rendered in moments.

And thus a wrapper was born.

More math stuff

Check out math-to-itex, which quickly parses out TeX notation from strings.

With it, you could do something fun like:

MathToItex(string).convert do |eq, type|
  svg_content = Mathematical.new(:base64 => true).render(eq)

  # create image tags of math with base64-encoded SVGs
  %|<img class="#{type.to_s}-math" data-math-type="#{type.to_s}-math" src="#{svg_content}"/>|
end

Troubleshooting

Issues building Lasem

If you're having issues building Lasem, or have Lasem already preinstalled, you should set the MATHEMATICAL_USE_SYSTEM_LASEM environment variable to skip the build:

• If you use bundler:

    MATHEMATICAL_USE_SYSTEM_LASEM=1 bundle install
  

• If you use gem install:

    MATHEMATICAL_USE_SYSTEM_LASEM=1 gem install mathematical
  

Issues with font alignment on OS X

If there's an issue with the resulting file(s) on OS X, chances are the problem is Cairo 1.14.2, which at the time of this writing, is the latest version of Cairo available on OS X via Homebrew.

This thread has more information on the problem and a possible work-around. For right now, it's suggested that you use an older (but still functional) version of Cairo and Pango:

brew install https://raw.githubusercontent.com/Homebrew/homebrew/26d5775494b3535820c48442c23af44f72974880/Library/Formula/cairo.rb
brew install https://raw.githubusercontent.com/Homebrew/homebrew/e8a4de3960191c5726084416a3b78c5fcd5a3b05/Library/Formula/pango.rb