fix loadImage for browsers

- closes #92

Author: samizdatco

lib/browser.js

@@ -9,9 +9,10 @@ const {asBuffer, asDownload, asZipDownload, atScale, options} = require('./io')
 
 const _toURL_ = Symbol.for("toDataURL")
 
-const loadImage = src => new Promise((onload, onerror) =>
-  Object.assign(new Image(), {crossOrigin:'Anonymous', onload, onerror, src})
-)
+const loadImage = src => {
+  let img = Object.assign(new Image(), {crossOrigin:'Anonymous', src})
+  return img.decode().then(() => img)
+}
 
 class Canvas{
   constructor(width, height){