从大图里边截取一部分显示，为啥显示不出来？

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let imgBig:Laya.Image=new Laya.Image();
imgBig.skin="big.jpg"; 
let imgCut:Laya.Image=new Laya.Image();
let texture:Laya.Texture=Laya.Texture.create(imgBig,0,0,100,100);
imgCut.texture=texture;
Laya.stage.addChild(imgCut);