Support canvas v1 & v2 API

src/index.js

@@ -7,12 +7,15 @@ const defaultOptions = {
 	Canvas: undefined
 };
 
+// Support canvas v1 & v2 API
+const createCanvas = Canvas => typeof Canvas === 'function' ? new Canvas() : Canvas.createCanvas();
+
 // Return Promise
 const mergeImages = (sources = [], options = {}) => new Promise(resolve => {
 	options = Object.assign({}, defaultOptions, options);
 
 	// Setup browser/Node.js specific variables
-	const canvas = options.Canvas ? new options.Canvas() : window.document.createElement('canvas');
+	const canvas = options.Canvas ? createCanvas(options.Canvas) : window.document.createElement('canvas');
 	const Image = options.Canvas ? options.Canvas.Image : window.Image;
 	if (options.Canvas) {
 		options.quality *= 100;