Added async toDataURL() support

lib/canvas.js

@@ -98,17 +98,33 @@ Canvas.prototype.createSyncPNGStream = function(){
 };
 
 /**
- * Return a data url.
+ * Return a data url. Pass a function for async support.
  *
- * @param {String} type
+ * @param {String|Function} type
+ * @param {Function} fn
  * @return {String}
  * @api public
  */
 
-Canvas.prototype.toDataURL = function(type){
-  // TODO: jpeg / svg / pdf :)
+Canvas.prototype.toDataURL = function(type, fn){
+  // Default to png
   type = type || 'image/png';
+
+  // Allow callback as first arg
+  if ('function' == typeof type) fn = type, type = 'image/png';
+
+  // Throw on non-png
   if ('image/png' != type) throw new Error('currently only image/png is supported');
-  return 'data:' + type
-    + ';base64,' + this.toBuffer().toString('base64');
+
+  var prefix = 'data:' + type + ';base64,';
+
+  if (fn) {
+    this.toBuffer(function(err, buf){
+      if (err) return fn(err);
+      var str = 'data:' + type
+      fn(null, prefix + buf.toString('base64'));
+    });
+  } else {
+    return prefix + this.toBuffer().toString('base64');
+  }
 };

test/canvas.test.js

@@ -242,7 +242,7 @@ module.exports = {
     assert.length(buf, 252);
   },
   
-  'test Canvas#toBuffer() async': function(assert, done){
+  'test Canvas#toBuffer() async': function(assert){
     new Canvas(200, 200).toBuffer(function(err, buf){
       assert.ok(!err);
       assert.equal('PNG', buf.slice(1,4).toString());
@@ -279,5 +279,19 @@ module.exports = {
       err = e;
     }
     assert.equal('currently only image/png is supported', err.message);
+  },
+  
+  'test Canvas#toDataURL() async': function(assert){
+    new Canvas(200,200).toDataURL(function(err, str){
+      assert.ok(!err);
+      assert.length(str, 358);
+    });
+  },
+  
+  'test Canvas#toDataURL() async with type': function(assert){
+    new Canvas(200,200).toDataURL('image/png', function(err, str){
+      assert.ok(!err);
+      assert.length(str, 358);
+    });
   }
 }