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图像获取与录制
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说明
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#. 使用前，请关闭ROS程序，摄像头只能同时被一个程序访问。
#. 参考下面的示例代码，更改 ``gstreamer_pipeline()`` 函数的默认参数，从而更改摄像头的配置参数。

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示例代码
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.. code-block:: python

   import cv2

   def gstreamer_pipeline(
       sensor_id=1,         # 摄像头编号
       capture_width=1280,  # 采集分辨率width
       capture_height=720,  # 采集分辨率height
       display_width=1280,
       display_height=720,
       framerate=60,        # 采集帧率
       flip_method=2,       # 视频翻转模式，因为模块的摄像头是反装的，所以使用2（180翻转）
   ):
       return (
           "nvarguscamerasrc sensor-id=%d ! "
           "video/x-raw(memory:NVMM), "
           "width=(int)%d, height=(int)%d, "
           "format=(string)NV12, framerate=(fraction)%d/1 ! "
           "nvvidconv flip-method=%d ! "
           "video/x-raw, width=(int)%d, height=(int)%d, format=(string)BGRx ! "
           "videoconvert !"
           "video/x-raw, format=(string)BGR ! appsink"
           % (
               sensor_id,
               capture_width,
               capture_height,
               framerate,
               flip_method,
               display_width,
               display_height,
           )
       )

   def show_camera():
       print(gstreamer_pipeline(flip_method=2))
       cap = cv2.VideoCapture(gstreamer_pipeline(flip_method=2), cv2.CAP_GSTREAMER)
       if cap.isOpened():
           window_handle = cv2.namedWindow("CSI Camera", cv2.WINDOW_AUTOSIZE)
           # Window
           while cv2.getWindowProperty("CSI Camera", 0) >= 0:
               ret_val, img = cap.read()
               cv2.imshow("CSI Camera", img)
               # This also acts as
               keyCode = cv2.waitKey(30) & 0xFF
               # Stop the program on the ESC key
               if keyCode == 27:
                   break
           cap.release()
           cv2.destroyAllWindows()
       else:
           print("Unable to open camera")


   if __name__ == "__main__":
       show_camera()