版本是 2dx 2.2.6, 想要使用CCClippingNode配合CCDrawNode绘制一个矩阵来裁剪HelloWorld.png，
但是没有成功，请问我有什么地方写错或者漏写了吗
CCClippingNode *clip=CCClippingNode::create();//创建裁剪节点，成员变量
clip->setContentSize(CCSizeMake(100, 100));
clip->setPosition(ccp(visibleSize.width/2 + origin.x, visibleSize.height/2 + origin.y));
clip->setAnchorPoint(ccp(0.5, 0.5));
clip->setInverted(true);
clip->setAlphaThreshold(0.00f);
clip->setTag(101);
this->addChild(clip,111);//添加裁剪节点
static CCPoint rectangle;
rectangle= ccp(0, 0);
rectangle= ccp(50,0);
rectangle= ccp(50,50);
rectangle= ccp(0, 50);
CCDrawNode *stencil = CCDrawNode::create();
static ccColor4F green = {0, 1, 0, 1};
stencil->drawPolygon(rectangle, 4, green, 0, green);
stencil->setPosition(ccp(0, 0));
stencil->setTag(100);
clip->setStencil(stencil);
CCSprite* bg = CCSprite::create(“HelloWorld.png”);
bg->setTag(20);
bg->setPosition(ccp(0,0));
clip->addChild(bg);