make pixel-input stream aware of area

lib/input_stream.js

@@ -24,7 +24,9 @@ define(function() {
             calculatedWidth,
             calculatedHeight,
             _eventNames = ['canrecord', 'ended'],
-            _eventHandlers = {};
+            _eventHandlers = {},
+            _topRight = {x: 0, y: 0},
+            _canvasSize = {x: 0, y: 0};
 
         function loadImages() {
             loaded = false;
@@ -41,6 +43,8 @@ define(function() {
                 calculatedWidth = _config.size ? width/height > 1 ? _config.size : Math.floor((width/height) * _config.size) : width;
                 calculatedHeight = _config.size ? width/height > 1 ? Math.floor((height/width) * _config.size) : _config.size : height;
 
+                _canvasSize.x = calculatedWidth;
+                _canvasSize.y = calculatedHeight;
 
                 setTimeout(function() {
                     publishEvent("canrecord", []);
@@ -124,6 +128,24 @@ define(function() {
             }
         };
 
+        that.setTopRight = function(topRight) {
+            _topRight.x = topRight.x;
+            _topRight.y = topRight.y;
+        };
+
+        that.getTopRight = function() {
+            return _topRight;
+        };
+
+        that.setCanvasSize = function(size) {
+            _canvasSize.x = size.x;
+            _canvasSize.y = size.y;
+        };
+
+        that.getCanvasSize = function() {
+            return _canvasSize;
+        };
+
         that.getFrame = function() {
             if (!loaded){
                 return null;