Add asynchronous open

examples/parse.js

 var PSD = require('../');
 
-psd = PSD.fromFile('./examples/images/example.psd');
-psd.parse();
-
-console.log(psd.header.export());
+psd = PSD.open('./examples/images/example.psd', function (psd) {
+  console.log(psd.header.export());
+  console.log(psd.tree().children()[0].children()[0].nextSibling().export());
+});
 // psd.image.saveAsPng('./output.png').then(function () {
 //   console.log("Finished!");
 // });
\ No newline at end of file
-
-console.log(psd.tree().children()[0].children()[0].nextSibling().export());
\ No newline at end of file

lib/psd.coffee

@@ -13,6 +13,13 @@ module.exports = class PSD
     Root: require('./psd/nodes/root.coffee')
 
   @fromFile: (file) -> new PSD fs.readFileSync(file)
+  @open: (file, cb) ->
+    fs.readFile file, (err, data) ->
+      throw err if err?
+      psd = new PSD(data)
+      psd.parse()
+
+      cb(psd)
 
   constructor: (data) ->
     @file = new File(data)

lib/psd/layer_mask.coffee

@@ -15,6 +15,14 @@ module.exports = class LayerMask
 
     return if maskSize <= 0
 
+    @parseLayers()
+    @parseGlobalMask()
+
+    @layers.reverse()
+
+    @file.seek finish
+
+  parseLayers: ->
     layerInfoSize = Util.pad2 @file.readInt()
 
     if layerInfoSize > 0
@@ -27,6 +35,4 @@ module.exports = class LayerMask
       for i in [0...layerCount]
         @layers.push new Layer(@file, @header).parse()
 
-    @layers.reverse()
-
+  parseGlobalMask: ->
\ No newline at end of file
-    @file.seek finish