Call captureScreen with arguments if passed.

index.js

@@ -19,8 +19,17 @@ bitmap.prototype.colorAt = function(x, y)
     return robotjs.getColor(this, x, y);
 };
 
-module.exports.screen.capture = function()
+module.exports.screen.capture = function(x, y, width, height)
 {
-    b = robotjs.captureScreen();
+    //If coords have been passed, use them.
+    if (typeof x !== "undefined" && typeof y !== "undefined" && typeof width !== "undefined" && typeof height !== "undefined")
+    {
+        b = robotjs.captureScreen(x, y, width, height);
+    }
+    else 
+    {
+        b = robotjs.captureScreen();
+    }
+
     return new bitmap(b.width, b.height, b.byteWidth, b.bitsPerPixel, b.bytesPerPixel, b.image);
 };