d3 → png

This is not really a library or a tool so much as it is a proof of concept in which we use d3.js and jsdom to generate SVG documents from the command line. Here's how to use it:

1. Install the Node prerequisites

$ npm install

2. Install ImageMagick

With your favorite package manager (brew, apt, etc.).

3. Write a rendering script

It should look like this:

module.exports = function(window, options, callback) {
  var d3 = window.d3,
      svg = d3.select("svg");
  // do something fancy with svg here
  callback(null, svg.node());
};

Your module.exports function whould accept the following arguments:

• window the DOM window for the current context. Get your reference to d3 via window.d3.
• options is a dictionary of command line options from optimist.
• callback is a function to call when you're done rendering, in the form callback(error, node). node may either by a d3 selection or a DOM node.

See circles.js for an example.

4. Run your script to create the SVG

Replace render.js with the path to your script:

$ node index.js render.js > output.svg

5. Convert your SVG to PNG

Using ImageMagick's convert utility:

$ convert -background none output.svg output.png

Automate it!

The included Makefile automates these steps with wildcard targets for %.svg and %.png:

# renders with circles.js
$ make circles.svg
# converts circles.svg to circles.png
$ make circles.png

As an added bonus, %.svg is a prerequisite of %.png, so the .svg will be generated automatically when you make the .png.

Providing options to your script

Command line options are parsed with optimist and passed as the second argument to your render function, so if you run:

$ node index.js --width 500 --height 100 render.js

Your render script will receive the following options object as its second argument:

{
  width: 500,
  height: 100
}