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Viz.js

This project is a Makefile for building Graphviz with Emscripten and a simple wrapper for using it in the browser.

Getting Viz.js

Install with Bower:

bower install viz.js

Or with npm:

npm install viz.js

Or download the viz.js "binary" from the releases page.

"Lite" Version

A smaller version of Viz.js can be downloaded from the releases page and is available in the Bower package. viz-lite.js omits Expat and the NEATO layout plugin.

API

Viz(src, options={ format="svg", engine="dot", scale, images=[{ path, width, height }], totalMemory=16777216 })

  • src is a string representing the graph to render in the DOT language.
  • options
    • format sets the output format, and may be one of "svg", "xdot", "plain", "ps", "json", or "png-image-element".
    • engine sets the Graphviz engine to use, and may be one of "circo", "dot", "neato", "osage", or "twopi".
    • scale sets the scale factor for the "png-image-element" format. If this is not specified, window.devicePixelRatio will be used if available, and 1 if not.
    • images specifies image dimensions to use when rendering nodes with image attributes. This is an array of objects, { href, width, height }. href may be a filename ("example.png"), a relative or absolute path ("/images/example.png"), or a URL ("http://example.com/image.png"). Dimensions may be specified with units: in, px, pc, pt, cm, or mm. If no units are given or dimensions are given as numbers, points (pt) are used. Graphviz does not actually load image data when this option is used — images are referenced with the dimensions given, eg, in SVG by an <image> element with width and height attributes.
    • files specifies files to make available to Graphviz using Emscripten's in-memory filesystem. This is an array of objects, { path, data }. path is a string and may be given as an absolute or relative path, and data is a string. Files are created relative to the root, which is the working directory.
    • totalMemory sets the total memory available for the Emscripten module instance. This should be a power of 2. The default of 16MB should be sufficient for most cases — only consider using a larger number if you run into the error "Cannot enlarge memory arrays".

Parses src and renders a graph according to the options given. Output is a string, except when using the "png-image-element" format, when it is an instance of HTMLImageElement.

For example:

result = Viz("digraph { a -> b; }");
result = Viz("digraph { a -> b; }", { format: "png-image-element", scale: 2 });
result = Viz("graph { n0 -- n1 -- n2 -- n3 -- n0; }", { engine: "neato" });
result = Viz("digraph { x -> y -> z; }", { format: "plain" });
result = Viz("digraph { a[image=\"test.png\"]; }", { images: [ { path: "test.png", width: "400px", height: "300px" } ] });

If Graphviz encounters an error, Viz will throw an Error object with the error message.

Viz.svgXmlToPngImageElement(svgXml[, scale[, callback]])

  • svgXml is an SVG XML string, as may be obtained from the Viz function using the "svg" format option.
  • scale sets the scale factor for the output. If this is not specified, window.devicePixelRatio will be used if available, and 1 if not.
  • callback is an optional Node-style callback. If specified, it is given two arguments, (err, image). If not specified, Viz.svgXmlToPngImageElement returns an instance of HTMLImageElement.

Converts svgXml to a PNG HTMLImageElement. If callback is specfied, image is loaded by the time the callback is invoked.

Viz.svgXmlToPngBase64(svgXml, scale, callback)

  • svgXml is an SVG XML string, as may be obtained from the Viz function using the "svg" format option.
  • scale sets the scale factor for the output. If this is given as undefined, window.devicePixelRatio will be used if available, and 1 if not.
  • callback is a Node-style callback. It is given two arguments, (err, data).

Converts svgXml to a PNG represented as a Base64 string. This function requires a callback, unlike svgXmlToPngImageElement.

Supported Graphviz features

These engines are supported:

  • circo
  • dot
  • fdp
  • neato
  • osage
  • twopi

These formats are supported:

  • svg
  • xdot
  • plain
  • ps
  • json

PNG output

Viz.js provides the "png-image-element" format in addition to the regular Graphviz formats. This returns an HTMLImageElement which can be inserted into the document.

image = Viz("digraph g { a -> b; }", { format: "png-image-element" });
document.body.appendChild(image);

However, this won't work in a Web Worker context. In that case, ask for the "svg" format in the worker and convert using the accessory function Viz.svgXmlToPngImageElement in the window context. See tests/png.js for an example.

Internet Explorer support

Internet Explorer 10 and 11 require Fabric.js as an optional dependency for PNG output. Viz.js will look for a fabric object as a member of the global object with a loadSVGFromString() function and use that if present.

Build

To build from source, you will need to install the Emscripten SDK.

To download the sources and build everything:

make