Welcome to Transbot SE repository

6. Web page real-time monitoring

6.1. Environment Construction

sudo apt-get install ros-melodic-async-web-server-cpp ros-melodic-web-video-server ros-melodic-usb-cam 

First make sure that the USB camera link is correct, enter the following command to check that the USB device number exists and is video0

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ll  /dev 

If the execute permission is not enough, you need to add the execute permission

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sudo chmod 777 /dev/video* 

6.2. modify the launch file

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sudo vim /opt/ros/melodic/share/usb_cam/launch/usb_cam-test.launch 

Keep hitting the keyboard [d] to delete everything. Click [i] on the keyboard to enter the edit mode, and write the following content into it.

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< launch > 
    < arg  name = "open_view"  default = "false" /> 
    < node  name = "usb_cam"  pkg = "usb_cam"  type = "usb_cam_node"  output = "screen" > 
        < param  name = "video_device"  value = "/dev/video0" /> 
        < param  name = "image_width"  value = "640" /> 
        < param  name = "image_height"  value = "480" /> 
        < param  name = "pixel_format"  value = "yuyv" /> 
        < param  name = "camera_frame_id"  value = "usb_cam" /> 
        < param  name = "io_method"  value = "mmap" /> 
    </ node > 
    <!-- web_video_server --> 
    < node  pkg = "web_video_server"  type = "web_video_server"  name = "web_video_server"  output = "screen" /> 
    <!-- image_view --> 
    < group  if = "$(arg open_view)" > 
        < node  name = "image_view"  pkg = "image_view"  type = "image_view"  respawn = "false"  output = "screen" > 
            < remap  from = "image"  to = "/usb_cam/image_raw" /> 
            < param  name = "autosize"  value = "true" /> 
        </ node > 
    </ group > 
</ launch > 

Click the [ESC] key twice (or multiple times), click the keyboard [shift plus;], enter [wq], and click the [Enter] key.

6.3. effect demonstration

open terminal, start

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roslaunch usb_cam usb_cam-test.launch  

• View in local web browser

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http://localhost:8080/ 

• View other devices (must be under the same LAN, 192.168.2.93 is the IP address of the master)

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http://192.168.2.93:8080/ 

Note: It is recommended to use Google Chrome or mobile QQ browser, other browsers may not be able to open the image

Click [image_raw] to view the camera image in real time, and click [Snapshot] to display only one frame of image.