svg2png-py 1.1.0

Thread-safe SVG → PNG rendering for Python, powered by resvg

svg2png-py

Fast, accurate SVG → PNG rendering for Python, powered by the resvg Rust library. Built with PyO3 and Maturin.

Unlike the original resvg-py, this binding is fully thread-safe: a FontDatabase instance can be shared across threads and called concurrently from a ThreadPoolExecutor without any locking on the Python side.

---

Features

• Full-fidelity SVG → PNG rasterization via resvg / tiny-skia
• Thread-safe FontDatabase — share one instance across a thread pool
• Affine-free transforms — pass a plain 6-tuple, no extra dependencies
• Batch rendering via render_many
• Background canvas: solid colour, existing PNG file, or raw PNG bytes
• Pre-built wheels for Windows, Linux, and macOS (Python ≥ 3.9)

---

Installation

pip install svg2png-py

---

Quick start

import svg2png_py

# Load fonts (system fonts + a custom one)
db = svg2png_py.FontDatabase.system()
db.load_font_file("/path/to/MyFont.ttf")

svg = open("diagram.svg", encoding="utf-8").read()

# Render with the SVG's intrinsic size
png_bytes = svg2png_py.svg_to_png(svg, db)
open("diagram.png", "wb").write(png_bytes)

---

API

FontDatabase

db = svg2png_py.FontDatabase()          # empty
db = svg2png_py.FontDatabase.system()   # pre-loaded with system fonts

db.load_system_fonts()                 # add system fonts to an existing db
db.load_font_file("/path/to/font.ttf") # load a single file
db.load_fonts_dir("/path/to/fonts/")   # load all fonts in a directory
len(db)                                # number of loaded font faces

---

RenderOptions

opts = svg2png_py.RenderOptions(
    dpi=96.0,                       # default: 96.0
    font_family="Helvetica",        # default: "Times New Roman"
    font_size=12.0,                 # default: 12.0
    resources_dir="/path/to/svgs/", # default: None (cwd)
)

---

svg_to_png

png: bytes = svg2png_py.svg_to_png(
    svg_str,            # str — SVG content
    font_db,            # FontDatabase
    transform=None,     # 6-tuple (a,b,c,d,e,f) or None for identity
    bg_file=None,       # str — path to a PNG background
    bg_data=None,       # bytes — raw PNG background
    bg_size=None,       # (w, h) — canvas size (default: SVG intrinsic)
    bg_color=None,      # (r, g, b, a) — fill colour 0-255
    options=None,       # RenderOptions
)

---

render_many

pages: list[bytes] = svg2png_py.render_many(
    svg_strings,        # list[str]
    font_db,            # FontDatabase
    transform=None,     # shared transform for all pages
    bg_color=None,      # shared fill colour for all pages
    options=None,       # shared RenderOptions
)

---

Transforms

The transform parameter accepts a 6-tuple (a, b, c, d, e, f) in row-major order. This is the same layout as affine.Affine(...)[0:6], so code that previously depended on the affine package can simply pass the slice directly — no library change needed:

# Before (affine required):
# from affine import Affine
# tr = Affine.scale(2)
# data = old_render(tree, tr[0:6])

# After (no extra dependency):
a, b, c, d, e, f = 2, 0, 0, 0, 2, 0   # scale ×2
png = svg2png_py.svg_to_png(svg, db, transform=(a, b, c, d, e, f))

Pass None (the default) for the identity transform.

---

Thread-pool example

import svg2png_py
from concurrent.futures import ThreadPoolExecutor

db = svg2png_py.FontDatabase.system()
svgs = [open(f"page{i}.svg").read() for i in range(20)]

def render_one(svg):
    return svg2png_py.svg_to_png(svg, db)   # db shared across threads ✓

with ThreadPoolExecutor() as pool:
    pngs = list(pool.map(render_one, svgs))

---

Credits

This package is a rewrite of resvg-py by Brice Yan, used under the MIT licence.

It wraps the resvg crate (formerly by RazrFalcon, now maintained by the Linebender project), which uses tiny-skia for rasterization and fontdb for font resolution.

---

License

MIT