Python API

import mermaidx

Functions

render(source, backend=None, **opts)

Render a Mermaid diagram and return a Diagram.

• source: the Mermaid text.
• backend: "quickjs" (default), "v8", "merman" or "mermaid-rs-renderer". A backend whose package is missing raises ImportError with an install hint.
• theme: "default", "forest", "dark" or "neutral".
• config: a dict of Mermaid configuration (quickjs and v8).
• css: CSS text to inject (quickjs and v8).
• node_spacing, rank_spacing, aspect_ratio: layout options of the Rust backends.
• raster: the SVG rasterizer. Only "novasvg" is supported. "resvg" raises a ValueError.

render_many(sources, *, workers=None, **opts)

Render a list of sources in parallel with a process pool and return the Diagram objects in the same order. workers defaults to the smaller of the number of sources and the CPU count. The other options are passed to every diagram.

render_ascii(source, **opts)

Return the diagram as text with box-drawing characters, for terminals. It is always available.

backends()

Return the names of the backends that can be used in this environment.

svg_to_png, svg_to_jpg, svg_to_image, svg_to_raw

Rasterize an SVG string you already have. For example, svg_to_png(svg, width=None, height=None, background=None) returns PNG bytes, and svg_to_jpg adds quality=90. svg_to_raw returns (bytes, width, height) with RGBA8888 pixels.

Diagram

Every method that produces output takes the same size options. When you give none, the diagram is rendered at its natural size.

Option	Meaning
width, height	Output size in pixels
scale	Size multiplier, used when width and height are omitted
background	CSS color, transparent by default

Results are cached per set of options, so calling d.svg() twice computes once.

Method	Returns
svg()	The SVG as str
png(width, height, scale, background)	PNG bytes
jpg(..., quality=90)	JPEG bytes. White background by default
bmp(...), tga(...)	BMP and TGA bytes
raw(...)	(bytes, width, height), RGBA8888
numpy(...)	numpy.ndarray, no Pillow needed
pdf(*, width, height, scale=1.0, background, pdf_format, pdf_landscape=False, pdf_margin="0")	PDF bytes. Fits the diagram unless pdf_format is given
ascii(**opts)	The diagram as text
save(output, ..., format=None, **format_opts)	Writes a file. The format comes from the extension, or from format
show()	Opens the diagram for viewing

d = mermaidx.render("flowchart LR; A-->B-->C")

d.save("out.png", width=1200)
d.save("out.jpg", quality=85)
d.save("out.pdf", pdf_format="A4", pdf_margin="1cm")
d.save("out.png.bak", format="png")      # force the format

In Jupyter, a Diagram renders itself as SVG when it is the last expression of a cell.