loadFromJSON method
http://fabricjs.com/docs/fabric.Canvas.html#loadFromJSON
Populates canvas with data from the specified JSON. JSON format must conform to the one of fabric.Canvas#toJSON
json
String | Object JSON string or jsObject
callback
function Callback, invoked when json is parsed and corresponding objects (e.g: fabric.Image) are initialized
reviver
function
Implementation
external Canvas loadFromJSON(json, Function callback, [Function reviveropt]);