xr-camera像普通camera一样可以把每帧的图像暴露出来

 this.cameraContext = wx.createCameraContext()
  const listener = this.cameraContext.onCameraFrame((frame) => {
    const frameData = new Uint8Array(frame.data);
    const clampedData = new Uint8ClampedArray(frameData);
    const imageData = this.canvas.createImageData(clampedData, frame.width, frame.height);
      ........
  });
  listener.start();