Introducing Starling

RenderTexture

The starling.textures.RenderTexture API, allows developers to create nondestructive drawing. As a Flash developer, think about the BitmapData API. This feature can be really useful when creating applications like drawing tools, where you need to draw continuously inside a texture and preserve previous drawings.

In the following code, we replicate the BitmapData.draw feature, on the GPU through Starling:

package
{
    import flash.display.Bitmap;
    import flash.geom.Point;

    import starling.display.Image;
    import starling.display.Sprite;
    import starling.events.Event;
    import starling.events.Touch;
    import starling.events.TouchEvent;
    import starling.events.TouchPhase;
    import starling.textures.RenderTexture;
    import starling.textures.Texture;

    public class Game extends Sprite
    {
        private var mRenderTexture:RenderTexture;
        private var mBrush:Image;

        [Embed(source = "/../media/textures/egg_closed.png")]
        private static const Egg:Class;

        public function Game()
        {
            addEventListener(Event.ADDED_TO_STAGE, onAdded);
        }

        private function onAdded (e:Event):void
        {
            // create a Bitmap object out of the embedded image
            var brush:Bitmap = new Egg();

            // create a Texture object to feed the Image object
            var texture:Texture = Texture.fromBitmap(brush);

            // create the texture to draw into the texture
            mBrush = new Image(texture);

            // set the registration point
            mBrush.pivotX = mBrush.width >> 1;
            mBrush.pivotY = mBrush.height >> 1;

            // scale it
            mBrush.scaleX = mBrush.scaleY = 0.5;

            // creates the canvas to draw into