// myCustomDisplayObject and myCustomMaskDisplayObject can be any Starling display object:
var myCustomDisplayObject:Sprite = new Sprite();
var myCustomMaskDisplayObject:Sprite = new Sprite();// for masks with animation: 较费，因为每次render都需要刷新RenderTexture，尽量避免同时出现大量这种带mask的动画。(宿主为动画或者mask本身也会动，都需要将animate设置成true)
var maskedDisplayObject:PixelMaskDisplayObject = new PixelMaskDisplayObject();
maskedDisplayObject.addChild(myCustomDisplayObject);// for masks with no animation (note, MUCH better performance!) 静态
var maskedDisplayObject:PixelMaskDisplayObject = new PixelMaskDisplayObject(-1, false);
maskedDisplayObject.addChild(myCustomDisplayObject);// Apply the masking as you would in classic flash.display style.
// Note: the mask display object should not be added to the display list.

maskedDisplayObject.mask = myCustomMaskDisplayObject; //mask基于像素，可以自定义形状，而不是传统的矩形viewport
addChild(maskedDisplayObject);

        private function refreshRenderTextures(e:Event=null) : void {if (_mask) {clearRenderTextures();_maskRenderTexture = new RenderTexture(_mask.width, _mask.height, false, _scaleFactor);_renderTexture = new RenderTexture(_mask.width, _mask.height, false, _scaleFactor);// create image with the new render texture_image = new Image(_renderTexture);// create image to blit the mask onto_maskImage = new Image(_maskRenderTexture);// set the blending mode to MASK (ZERO, SRC_ALPHA)　　　　　　　　  // BlendMode.register(MASK_MODE_NORMAL,Context3DBlendFactor.ZERO,Context3DBlendFactor.SOURCE_ALPHA);　　　　　　　　　// BlendMode.register(MASK_MODE_INVERTED,Context3DBlendFactor.ZERO,Context3DBlendFactor.ONE_MINUS_SOURCE_ALPHA);                if (_inverted) {_maskImage.blendMode = MASK_MODE_INVERTED;} else {_maskImage.blendMode = MASK_MODE_NORMAL;}}_maskRendered = false;}

        private function drawRenderTextures() : void{// undo scaling and positioning temporarily because its already applied in this execution stackvar matrix:Matrix = this.transformationMatrix.clone();this.transformationMatrix = new Matrix();_superRenderFlag = true;            _renderTexture.draw(this);_superRenderFlag = false;this.transformationMatrix = matrix;_renderTexture.draw(_maskImage);}

        public override function render(support:RenderSupport, parentAlpha:Number):void{if (_isAnimated || (!_isAnimated && !_maskRendered)) {if (_superRenderFlag || !_mask) {super.render(support, parentAlpha);} else {            if (_mask) {                   _maskRenderTexture.draw(_mask);_renderTexture.drawBundled(drawRenderTextures);                _image.render(support, parentAlpha);_maskRendered = true;}}} else {_image.render(support, parentAlpha);}}