ROS学习笔记（三）：在ROS中使用USB网络摄像头传输图像
在上节已经实现了单张图片的ROS实现，而在现实中，我们一般是使用摄像头来获取图像，这次要实现在ROS中使用摄像头传输图像，我使用的是罗技的usb网络摄像头，首先我们需要获取摄像头的型号,如下所示:
yake@yake-K42JE:~$ lsusb Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 003: ID 04f2:b1e5 Chicony Electronics Co., Ltd Bus 002 Device 003: ID 046d:c058 Logitech, Inc. M115 Mouse Bus 002 Device 008: ID 046d:0825 Logitech, Inc. Webcam C270
我所使用的是罗技的C270网络摄像头.接下来我们要为摄像头安装驱动,我使用的是cheese点击打开链接,这个驱动的好处是在ubuntu环境下直接apt-get获得
yake@yake-K42JE:~$ sudo apt-get install cheese
安装完成后,插上摄像头可以发现在dev/目录下多了一个viedo0的设备,这个说明摄像头驱动已经安装完成.接下来开始在ROS中使用它.使用的方式是通过opencv函数来实现.
首先还是要创建一个包,写一个驱动摄像头的文件,命名为my_publisher.cpp,作用是获取图像并打包成ros格式发送出去,创建包的方法与单张图片一样,my_publisher.cpp内容如下:
#include <ros/ros.h>
#include <image_transport/image_transport.h>
#include <opencv2/highgui/highgui.hpp>
#include <cv_bridge/cv_bridge.h>
#include <sstream> // for converting the command line parameter to integer
int main(int argc, char** argv)
{
// Check if video source has been passed as a parameter
if(argv[1] == NULL)
{
ROS_INFO("argv[1]=NULL\n");
return 1;
}
ros::init(argc, argv, "image_publisher");
ros::NodeHandle nh;
image_transport::ImageTransport it(nh);
image_transport::Publisher pub = it.advertise("camera/image", 1);
// Convert the passed as command line parameter index for the video device to an integer
std::istringstream video_sourceCmd(argv[1]);
int video_source;
// Check if it is indeed a number
if(!(video_sourceCmd >> video_source))
{
ROS_INFO("video_sourceCmd is %d\n",video_source);
return 1;
}
cv::VideoCapture cap(video_source);
// Check if video device can be opened with the given index
if(!cap.isOpened())
{
ROS_INFO("can not opencv video device\n");
return 1;
}
cv::Mat frame;
sensor_msgs::ImagePtr msg;
ros::Rate loop_rate(5);
while (nh.ok()) {
cap >> frame;
// Check if grabbed frame is actually full with some content
if(!frame.empty()) {
msg = cv_bridge::CvImage(std_msgs::Header(), "bgr8", frame).toImageMsg();
pub.publish(msg);
//cv::Wait(1);
}
ros::spinOnce();
loop_rate.sleep();
}
}
再写一个my_subscriber.cpp,作用是获取ROS图像并显示,内容如下:
#include <ros/ros.h>
#include <image_transport/image_transport.h>
#include <opencv2/highgui/highgui.hpp>
#include <cv_bridge/cv_bridge.h>
void imageCallback(const sensor_msgs::ImageConstPtr& msg)
{
try
{
cv::imshow("view", cv_bridge::toCvShare(msg, "bgr8")->image);
// cv::WaitKey(30);
}
catch (cv_bridge::Exception& e)
{
ROS_ERROR("Could not convert from '%s' to 'bgr8'.", msg->encoding.c_str());
}
}
int main(int argc, char **argv)
{
ros::init(argc, argv, "image_listener");
ros::NodeHandle nh;
cv::namedWindow("view");
cv::startWindowThread();
image_transport::ImageTransport it(nh);
image_transport::Subscriber sub = it.subscribe("camera/image", 1, imageCallback);
ros::spin();
cv::destroyWindow("view");
}
接下来要把设计到的各种包和opencv在CmakeList中声明一下,添加以下语句
find_package(OpenCV REQUIRED)
# add the publisher example
add_executable(my_publisher src/my_publisher.cpp)
target_link_libraries(my_publisher ${catkin_LIBRARIES} ${OpenCV_LIBRARIES})
# add the subscriber example
add_executable(my_subscriber src/my_subscriber.cpp)
target_link_libraries(my_subscriber ${catkin_LIBRARIES} ${OpenCV_LIBRARIES})
将这个包进行编译
yake@yake-K42JE:~/ros_ws$ catkin_make
编译过程可能会出现错误,其中一个就是cv::WaitKey不能识别,这个问题到最后依然没有解决,我是直接把它注释掉,这样也没什么影响.接下来开始运行程序,首先启动ROS.
yake@yake-K42JE:~$ roscore
运行my_publisher节点.(如果运行不起来,需要先source devel/setup.bash)
yake@yake-K42JE:~/video_ros$ rosrun learning_image_transport my_publisher 0这时候会看到我们的摄像头灯已经亮起来了,0代表默认摄像头,如果有多个摄像头,则第二个是1,依次类推.
接下来运行my_subscriber节点来接收图像
yake@yake-K42JE:~/video_ros$ rosrun learning_image_transport my_subscriber
这时候如果没有错误的话就会弹出图像窗口
可以看到我们摄像头传输出来的图像，到此，整个程序结束！