fondi 0.2.1.dev21

LaTeX-like math renderer with PNG and SVG output

A simple mathematical LaTeX renderer for Python. Output as PNG (Pillow) or SVG (vector text with New Computer Modern).

Installation

pip install fondi

Requires Python 3.8+, Pillow, and NumPy.

Quick start

import fondi

mt = fondi.MathText(r"\frac{1}{2}", fontSize=50, color=(255, 255, 255, 255))

mt.to_pil().save("formula.png")   # raster
mt.save_svg("formula.svg")        # small SVG + external fonts (default)

MathText arguments

Argument	Type	Description
text	str	Fondi math string (LaTeX-like, not full LaTeX).
fontSize	int	Nominal size in pixels (same scale as the PNG renderer).
color	(R, G, B, A)	Each channel 0–255.

Output methods

Method	Returns	Use for
to_pil()	PIL.Image	Matplotlib, GUIs, notebooks, textures.
to_svg(...)	str	SVG XML; you control where files are written.
save_svg(path, ...)	Path	Write SVG to disk; optional font copy.
scene()	Scene	Inspect layout primitives (advanced).
image	PIL.Image	Same as to_pil() (backward compatible).

---

SVG export and fonts

Text in SVG uses New CM10 (NewCM10-Regular.otf / NewCM10-Italic.otf from the package). Integrals and braces are still embedded PNGs inside the SVG (v1).

You choose how those OTF files are shipped:

Mode	SVG size	Font files	Best for
Embedded	Large (~1 MB+)	Inside the SVG	Single file, email, simple hosting
External + copy	Small (few KB)	Copied next to the SVG	First export in a project
External, no copy	Small	You provide them	Many SVGs sharing one fonts/ folder

1. Embedded fonts (self-contained)

Every to_svg() call includes both full OTF files as base64 in <defs>. No separate font files; viewers need nothing installed.

svg = mt.to_svg()                                    # default
svg = mt.to_svg(embed_fonts=True)

with open("formula.svg", "w") as f:
    f.write(svg)

mt.save_svg("formula.svg", embed_fonts=True)

2. External fonts (small SVG)

The SVG references OTF files by URL, e.g. fonts/NewCM10-Regular.otf. You must keep those paths valid relative to where the SVG is opened (browser, Inkscape, etc.).

to_svg() — string only

svg = mt.to_svg(embed_fonts=False, font_url_prefix="fonts/")
# Writes no font files. You place the OTFs yourself.

Parameter	Default	Meaning
embed_fonts	True	False → external @font-face URLs.
font_url_prefix	""	Directory prefix in the URL, e.g. "fonts/" or "" if OTFs sit beside the SVG.

Copy fonts once from the package:

from fondi.backends import copy_font_files

copy_font_files("shared/fonts/")
# Creates shared/fonts/NewCM10-Regular.otf and NewCM10-Italic.otf

Then export many formulas pointing at the same folder:

for name, tex in formulas.items():
    m = fondi.MathText(tex, 24, (0, 0, 0, 255))
    with open(f"out/{name}.svg", "w") as f:
        f.write(m.to_svg(embed_fonts=False, font_url_prefix="../shared/fonts/"))

save_svg() — write file (+ optional font copy)

mt.save_svg("out/formula.svg")

Defaults: embed_fonts=False, font_subdir="fonts", copy_fonts=True.

Parameter	Default	Meaning
embed_fonts	False	True → one large self-contained SVG.
font_subdir	"fonts"	Subfolder under the SVG’s parent for OTF files and URL prefix ("fonts/"). Use None for OTFs in the same directory as the SVG.
copy_fonts	True	Copy bundled OTFs into font_subdir. False → only write the SVG (fonts must already exist there).

Copy fonts once per output tree:

mt.save_svg("out/formula.svg", embed_fonts=False, font_subdir="fonts")

out/
  formula.svg
  fonts/
    NewCM10-Regular.otf
    NewCM10-Italic.otf

SVG only (fonts already present):

from fondi.backends import copy_font_files

copy_font_files("out/fonts/")   # once

for i, tex in enumerate(items):
    fondi.MathText(tex, 20, (0, 0, 0, 255)).save_svg(
        f"out/label_{i}.svg",
        embed_fonts=False,
        font_subdir="fonts",
        copy_fonts=False,
    )

OTFs beside the SVG (no subfolder):

mt.save_svg("out/formula.svg", embed_fonts=False, font_subdir=None)
# Expects out/NewCM10-Regular.otf next to out/formula.svg
# URLs in SVG: NewCM10-Regular.otf (no prefix)

Choosing a mode (cheat sheet)

# One file, simplest sharing
mt.save_svg("x.svg", embed_fonts=True)

# Project with assets/fonts/ reused everywhere
copy_font_files("assets/fonts/")
mt.save_svg("plots/a.svg", embed_fonts=False, font_subdir="fonts", copy_fonts=False)
# Ensure font_subdir resolves from plots/a.svg → often use font_url_prefix like "../assets/fonts/"
# via to_svg(), or place fonts relative to each SVG accordingly

For nested paths, prefer to_svg(embed_fonts=False, font_url_prefix="...") with a prefix that matches your real directory layout.

Low-level API

from fondi.backends import render_svg, save_svg_bundle, copy_font_files

scene = mt.scene()
svg = render_svg(scene, embed_fonts=False, font_url_prefix="fonts/")
save_svg_bundle(scene, "out.svg", embed_fonts=False, font_subdir="fonts", copy_fonts=False)

---

PNG export

Raster output bakes the font into pixels. No font files are needed at view time.

img = mt.to_pil()
img.save("formula.png")
mt.image.save("formula.png")   # equivalent

---

Architecture

Layouts position math and emit a backend-neutral scene graph (TextRun, Line, RasterSymbol, …). Renderers turn the same scene into PNG or SVG — new macros are implemented once.

Layer	Role
layout/*, plain/plain.py	Geometry + scene primitives only
metrics.py	Font measurement (single source)
scene.py	Data types
backends/pillow.py, backends/svg.py	PNG / SVG output

Adding a macro (write once)

1. Add FooLayout(Layout) under src/fondi/layout/.
2. Register MACROS["\\foo"] = FooLayout.
3. Position children with boundingBox, setCenter, etc.
4. Implement collect_scene(offset) returning TextRun, Line, RasterSymbol, … — no Pillow or SVG code in the layout.
5. Run tests/test.py (PNG) and tests/test_svg.py (SVG smoke).

Features

• Parentheses
• Subscript / superscript
• Delimiters ((), [], cases {) as vector paths; integrals still PNG (v1)
• Fractions
• Cases
• Greek letters
• Square root
• Integrals

Tests

cd tests && python test.py      # regenerate PNG golden images
cd tests && python test_svg.py  # SVG smoke (embedded + external fonts)