mathjax.cr

Русская версия

A Crystal port of the MathJax (v3) core: TeX / AsciiMath / MathML → internal MML tree → MathML / HTML / SVG.

Ported after the ts/ sources of mathjax-src and the MathJax v2 font data:

Inputs

• TeX parser (input/tex): tokenizer, {...} groups, ^/_ scripts, primes, the \frac family, generalized fractions (a \over b, \atop, \choose, \above, \genfrac), \sqrt/\root, \left...\right with \middle, environments (matrix/pmatrix/bmatrix/vmatrix/Vmatrix/cases/ array/aligned/...), fonts (\mathrm, \mathbf, \mathbb, ...), accents (\vec, \hat, \overline, \overrightarrow, ...), spacing, \text, \stackrel, \overbrace/\underbrace, \phantom, \boxed, big operators with limits (munderover, \limits/\nolimits), \def/ \newcommand macros (with #1..#9).
• Extensions: color (\color, \textcolor, \definecolor with rgb/RGB/gray/HTML/cmyk models, \colorbox, \fcolorbox), cancel (\cancel, \bcancel, \xcancel, \sout), a physics subset (\abs, \norm, \dv, \pdv, \dd, \bra, \ket, \braket, \mel, \comm, ... — enabled via physics: true / --physics).
• AsciiMath (an input/asciimath subset): a/b fractions, ^/_, greek names, sum/prod/int with limits, relations and arrows (<= >= != -> => <=>), sqrt, hat/bar/vec/ul(...), |x|, floor/ceil, [[a,b],[c,d]] matrices, "..." text.
• MathML input (input/mml): XML → tree (round-trips with the serializer).

Outputs

• MathML — tree serialization.
• HTML — a simplified CommonHTML analogue: spans + CSS (MathJax.css).
• SVG — two modes (MathJax.to_svg(tex, paths: ...)):
  • paths: false (default): metrics-based typesetting with <text> + system fonts;
  • paths: true: MathJax v3 structure — glyph outline <path>s in a single <defs> + <use xlink:href>, sized in ex, colored via currentColor. The layout engine is a port of the mathjax-full v3 common wrappers (TeX spacing matrix, fraction/script/sqrt geometry, mtable layout, stretchy delimiter assembly, mo/accent remaps). Rasterizes by nanosvg.cr (egui-cr) with no fonts installed. Glyph outlines come from the TeX font data generated out of mathjax-full (tools/gen_svg_fonts.py, self-checked against the dataset: 7920/7920 d-strings byte-equal). Positional verification over the 1000-formula corpus: 96.6% of reference glyphs matched, median residual 13 units (1 em = 1000 units). See SVG_V3_PLAN.md.

Not ported

a11y (SRE — a separate large system), CHTML (the SVG output has two modes: <text> + system fonts, and the v3-structure path output — see "Outputs"), the action, autobold, bbox, bussproofs, cancel color options, centernot, colortbl, empheq, extpfeil, gensymb, html, mathtools, mhchem, newcommand conditionals, noerrors configurations, upgreek, verb extensions and the full AMS table (~180 base commands covered).

Installation

dependencies:
  mathjax:
    git: https://github.com/OrelSokolov/mathjax.cr

Usage

require "mathjax"

MathJax.to_mathml("\\frac{1}{2}")                   # MathML
MathJax.to_mathml("x^2", display: true)
MathJax.to_html("\\sqrt{2}")                        # HTML + mjx-* classes
MathJax.to_svg("\\frac{a+b}{c}")                    # SVG with TeX metrics
MathJax.css                                         # CSS for the HTML output
MathJax.parse("\\sum_{i=1}^n i")                    # => MathJax::Mml::Node
MathJax.to_mathml("\\abs{x}", physics: true)        # physics extension
MathJax::Mml::Serializer.call(
  MathJax.parse_asciimath("sum_(i=1)^n i"))         # AsciiMath input
MathJax.from_mathml("<math>...</math>")             # MathML input
MathJax::Fonts.width('a', "math_italic")            # 0.529 (TeX metrics)

Parse errors: MathJax::TeX::TexError, MathJax::AsciiMath::AsciiMathError, MathJax::Mml::MathmlError.

CLI

crystal run src/cli.cr -- --html --display < formula.tex
crystal run src/cli.cr -- --svg < formula.tex
crystal run src/cli.cr -- --physics --mml <<< '\dv{f}{x}'
crystal run src/cli.cr -- --ascii --mml <<< 'sum_(i=1)^n i'
echo '\frac{-b\pm\sqrt{b^2-4ac}}{2a}' | crystal run src/cli.cr

Tests

crystal spec   # 83 examples, including dataset thresholds

Integration testing (1-to-1 against MathJax)

1000 TeX formulas from English Wikipedia are run through mathjax.cr and through real MathJax (mathjax-full); the MathML trees are compared after normalization (see test/datasets/REPORT.md):

• 99.3% of formulas parsed (993/1000);
• 99.1% structurally identical trees (990/999 comparable).

crystal run tools/compare.cr        # full report + diffs.txt
crystal run tools/dump_one.cr -- 91 # ours vs ref trees for formula #91

The dataset and the reference are rebuildable: tools/fetch_formulas.cr (Wikipedia API) and tools/make_reference.js (node + mathjax-full).

A golden SVG dataset (1000 formulas with expected output from the original MathJax v3) lives in dataset/ — see dataset/README.md.

Layout

src/mathjax.cr                 public API
src/mathjax/tex/{parser,symbols}.cr     TeX input (input/tex port)
src/mathjax/asciimath/parser.cr         AsciiMath input
src/mathjax/mml/                         MML tree, serializer, MathML input
src/mathjax/html/renderer.cr            HTML output
src/mathjax/svg/renderer.cr             SVG output (metrics-based)
src/mathjax/fonts/tex_metrics.cr        TeX font glyph table (generated)
vendor/                                  MathJax sources (reference only)

License

Apache-2.0 (as is MathJax itself). mathjax.cr is an independent Crystal implementation; the font metrics are taken from MathJax data (Apache-2.0).