source devel/setup.*sh roslaunch usb_cam usb_cam-test.launch
rqt_graph查看动态消息图 当咱们把鼠标放在/usb_cam/image_raw上面,相应的node(蓝色和绿色)和topic(红色)高亮node
查看话题类型 rostopic type /usb_cam/image_raw 打印结果为sensor_msgs/Image
rosrun image_view image_view image:=xxcode