Cytosnap

Render graphs on the server side with Cytoscape.js, getting image files as output. This package uses Puppeteer to generate the output. Refer to the Puppeteer documentation to ensure that your machine is configured properly to run Chrome headlessly.

This project was initiated at MozSprint 2016

How to contribute

Please refer to CONTRIBUTING.md.

Usage

Quick start example:

var cytosnap = require('cytosnap');

// list of layout extensions to use
// NB you must `npm install` these yourself for your project
cytosnap.use([ 'cytoscape-dagre', 'cytoscape-cose-bilkent' ]);

var snap = cytosnap();

snap.start().then(function(){
  return snap.shot({
    elements: [ // http://js.cytoscape.org/#notation/elements-json
      { data: { id: 'foo' } },
      { data: { id: 'bar' } },
      { data: { source: 'foo', target: 'bar' } }
    ],
    layout: { // http://js.cytoscape.org/#init-opts/layout
      name: 'grid' // you may reference a `cytoscape.use()`d extension name here
    },
    style: [ // http://js.cytoscape.org/#style
      {
        selector: 'node',
        style: {
          'background-color': 'red'
        }
      },
      {
        selector: 'edge',
        style: {
          'line-color': 'red'
        }
      }
    ],
    resolvesTo: 'base64uri',
    format: 'png',
    width: 640,
    height: 480,
    background: 'transparent'
  });
}).then(function( img ){
  // do whatever you want with img
  console.log( img );
});

cytosnap.use()

Pull in layout extensions that you may used in the exported images:

cytosnap.use([ 'cytoscape-dagre', 'cytoscape-cose-bilkent' ]);

Each string is an npm package name that can be pulled in by require(). The list of extension package names that you specify is static: You may specify the list only once, so make sure the list includes all layouts you want to run. Every snap object shares the same extension list.

cytosnap()

Initialise an instance of Cytosnap:

var options = {};

var snap = cytosnap(options);

// or

var snap = new cytosnap(options);

The options you can pass include:

• puppeteer : An options object to pass to launch().
  • puppeteer.headless is true by default.
  • See the Puppeteer docs for the list of available options.
  • This is useful for disabling Chrome's sandbox for Travis via puppeteer.args. See the Puppeteer docs for more info.

snap.start( [next] )

Start up the Cytosnap instance, snap, so we can request that it generate images:

Promise style:

snap.start().then(function(){ // promise resolved on start
  console.log('chained start promise');
});

Node callback style using next:

snap.start(function( err ){
  console.log('called on start');
});

snap.shot( options, [next] )

Generate a snapshot of a graph:

var defaultOptions = {
  // cytoscape.js options
  elements: undefined, // cytoscape.js elements json
  style: undefined, // a cytoscape.js stylesheet in json format (or a function that returns it)
  layout: undefined // a cytoscape.js layout options object (or a function that returns it)
  // (specifying style or layout via a function is useful in cases where you can't send properly serialisable json)

  // image export options
  resolvesTo: 'base64uri', // output, one of 'base64uri' (default), 'base64', 'stream', or 'json' (export resultant node positions from layout)
  format: 'png', // 'png' or 'jpg'/'jpeg' (n/a if resolvesTo: 'json')
  quality: 85, // quality of image if exporting jpg format, 0 (low) to 100 (high)
  background: 'transparent', // a css colour for the background (transparent by default)
  width: 200, // the width of the image in pixels
  height: 200 // the height of the image in pixels
};

// promise style
snap.shot( defaultOptions ).then(function( img ){
  console.log('on resolve');
}).catch(function( err ){
  console.log('on error');
});

// node callback style
snap.shot( defaultOptions, function( err, img ){
  console.log('on error or resolve');
} );

snap.stop( [next] )

Stop the Cytosnap instance:

Promise style:

snap.stop().then(function(){ // promise resolved on stop
  console.log('chained stop promise');
});

Node callback style using next:

snap.stop(function( err ){
  console.log('called on stop');
});

Targets

• npm test : Run Mocha tests in ./test