heatmap.js is a JavaScript library that can be used to generate web heatmaps with the html5canvas element based on your data.

Heatmap instances contain a store in order to colorize the heatmap based on relative data, which means if you're adding only a single datapoint to the store it will be displayed as the hottest(red) spot, then adding another point with a higher count, it will dynamically recalculate. The heatmaps are fully customizable - you're welcome to choose your own color gradient, change its opacity, datapoint radius and many more.

Just add heatmap.js to your webpage and it will create one global object called heatmapFactory which you also can access as h337. This global object has a function create that takes one argument config (Object) and returns a heatmap instance. At the configuration object you can specify the following properties in order to customize your heatmap instance:

• radius (optional) Number. That's the radius of a single datapoint in the heatmap** (measured in pixels). Default is 40
• element (required) String|HTMLelement. Either provide an element's id or the element itself which should contain the heatmap.
• visible (optional) Boolean. Whether the heatmap is visible or not. Default is true
• gradient (optional) Object. An object which contains colorstops from 0 to 1. Default is the standard heatmap gradient.
• opacity (optional) Number [0-100]. Opacity of the heatmap measured in percent.

Here is an example instanciation:

var config = {
    "radius": 30,
    "element": "heatmapEl",
    "visible": true,
    "opacity": 40,
    "gradient": { 0.45: "rgb(0,0,255)", 0.55: "rgb(0,255,255)", 0.65: "rgb(0,255,0)", 0.95: "yellow", 1.0: "rgb(255,0,0)" }
};

var heatmap = heatmapFactory.create(config);

After creating the heatmap object you can set a dataset (import), add single datapoints and export the datapoints:

// set a dataset
heatmap.store.setDataSet({ max: 10, data: [{x: 10, y: 20, count: 5}, ...]});

// add a single datapoint
heatmap.store.addDataPoint(10, 20);

// export the dataset
var dataSet = heatmap.store.exportDataSet();

As you can see a heatmap instance contains a store which stores its datapoints. A store has the following functions:

• setDataSet(Object) void. This initializes the heatmap with a dataset. The dataset object has to have the following structure: {max: , data:[{x: , y: , count: },...]}
• addDataPoint(Number, Number, [Number]) void. Adds a single datapoint to the store. First parameter is x, second parameter is y. Third parameter is the value, if not specified 1 will be used.
• exportdataSet() Object. Returns the store's data as an object with the same structure that the import object at setDataSet has.

heatmap.js is dual-licensed under the MIT and the Beerware license, feel free to use it in your projects.

Feel free to contact me:
on my website patrick-wied.at
via twitter @patrickwied
or email [email protected]