usb_cam的ROS2甜点

Posted 2021-10-01 zhangrelay

最近收到一些反馈，不多但是都非常有价值，感谢反馈的朋友们。关于ROS2的实践和应用类型课程已经开发完成，ROS1最终版Noetic也会出一版纪念版镜像配合教程，但博客更新主要集中于ROS2的相关应用。

usb_cam这是非常典型有价值的摄像头包。主要有两个：

• ros2_usb_camera-foxy-devel
• usb_cam-ros2

代码差异还是有不少的。

推荐使用usb_cam。

•  ros2 launch usb_cam demo_launch.py 

效果如下：

这个是640*480

如果需要1280*720，需要修改如下：

usb_cam_node.cpp

  // declare params
  this->declare_parameter("camera_name", "default_cam");
  this->declare_parameter("camera_info_url", "");
  this->declare_parameter("framerate", 10.0);
  this->declare_parameter("frame_id", "default_cam");
  this->declare_parameter("image_height", 720);
  this->declare_parameter("image_width", 1280);
  this->declare_parameter("io_method", "mmap");
  this->declare_parameter("pixel_format", "yuyv");
  this->declare_parameter("video_device", "/dev/video0");

这样就可以吗？应该是不行的，还需要的操作如下：

先看下启动文件launch

# Copyright 2018 Lucas Walter
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#
# Software License Agreement (BSD License 2.0)
#
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# modification, are permitted provided that the following conditions
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#    with the distribution.
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#    from this software without specific prior written permission.
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# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.


import argparse
from launch import LaunchDescription
from launch_ros.actions import Node

import os
import sys

from ament_index_python.packages import get_package_share_directory


def generate_launch_description():
    ld = LaunchDescription()

    parser = argparse.ArgumentParser(description='usb_cam demo')
    parser.add_argument('-n', '--node-name', dest='node_name', type=str,
                        help='name for device', default='usb_cam')

    args, unknown = parser.parse_known_args(sys.argv[4:])

    usb_cam_dir = get_package_share_directory('usb_cam')

    # get path to params file
    params_path = os.path.join(
        usb_cam_dir,
        'config',
        'params.yaml'
    )

    node_name = args.node_name

    print(params_path)
    ld.add_action(Node(
        package='usb_cam', executable='usb_cam_node_exe', output='screen',
        name=node_name,
        # namespace=ns,
        parameters=[params_path]
        ))
    ld.add_action(Node(
        package='usb_cam', executable='show_image.py', output='screen',
        # namespace=ns,
        # arguments=[image_manip_dir + "/data/mosaic.jpg"])
        # remappings=[('image_in', 'image_raw')]
        ))

    return ld

注意到如下这一段：

    # get path to params file
    params_path = os.path.join(
        usb_cam_dir,
        'config',
        'params.yaml'
    )

需要修改啦：

camera_info.yaml

image_width: 1280
image_height: 720
camera_name: test_camera
camera_matrix:
  rows: 3
  cols: 3
  data: [438.783367, 0.000000, 305.593336, 0.000000, 437.302876, 243.738352, 0.000000, 0.000000, 1.000000]
distortion_model: plumb_bob
distortion_coefficients:
  rows: 1
  cols: 5
  data: [-0.361976, 0.110510, 0.001014, 0.000505, 0.000000]
rectification_matrix:
  rows: 3
  cols: 3
  data: [0.999978, 0.002789, -0.006046, -0.002816, 0.999986, -0.004401, 0.006034, 0.004417, 0.999972]
projection_matrix:
  rows: 3
  cols: 4
  data: [393.653800, 0.000000, 322.797939, 0.000000, 0.000000, 393.653800, 241.090902, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000]

params.yaml

/**:
    ros__parameters:
      video_device: "/dev/video0"
      framerate: 30.0
      io_method: "mmap"
      frame_id: "camera"
      pixel_format: "yuyv"
      image_width: 1280
      image_height: 720
      camera_name: "test_camera"
      camera_info_url: "package://usb_cam/config/camera_info.yaml"

参数合适吗？不管，效果还是有的：

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然后，就可以愉快玩耍各种图形处理算法啦，欢乐不^_^

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