public static Texture2D CaptureCamera(Camera camera, Rect rect)

        {

            RenderTexture rt = new RenderTexture((int)rect.width, (int)rect.height, );

            RenderTexture originRtt = null;

            Camera currCam = null;

            foreach (Camera cam in Camera.allCameras)

            {

                if (null != cam.targetTexture) continue;

                currCam = cam;

                originRtt = currCam.targetTexture;

                cam.targetTexture = rt;

                cam.RenderDontRestore();          //手动渲染

                cam.targetTexture = originRtt;    //注意: 需要该操作，不然会报错

            }

            //激活rt并从中读取像素

            RenderTexture.active = rt;

            Texture2D screenShot = new Texture2D((int)rect.width, (int)rect.height, TextureFormat.RGB24, false);

            screenShot.ReadPixels(rect, , );  //这个时候是从  RenderTexture.active 中读取数据

            screenShot.Apply();                 //这是非常消耗性能的操作，操作之前尽量多读取像素

            currCam.targetTexture = null;

            GameObject.Destroy(rt);

            RenderTexture.active = null;

            //生成 .png 快照

            byte[] bytes = screenShot.EncodeToPNG();

            string filename = Application.dataPath + "/Screenshot.png";

            System.IO.File.WriteAllBytes(filename, bytes);

            Debug.Log("生成了一张屏幕快照");

            return screenShot;

        }

UITexture m_TxBG.mainTexture = CaptureCamera(NGUITools.FindCameraForLayer(this.gameObject.layer), new Rect(, , Screen.width, Screen.height));