QT ROS related operations (running Terminal instructions, publishing and subscribing to custom message topics or services, subscribing to images and displaying)

01 Run terminal instructions

Configure remote login

ssh-keygen -t rsa
#  Then keep going back 

ssh-copy-id [email protected] Address 
#  Then enter the password 

ssh [email protected] Address 

02 Publish and subscribe to custom message topics or services

2.1 Create nodes to subscribe to publish topics

• Be careful ：
  1、 Frequency is modified qnode Class run Function ros::Rate loop_rate(10);, At first I deleted while What's inside , Later, I found that for subscribing to video topics , The rating needs to be revised a little larger .
  2、 stay QNode::init() Declare the name of subscription and publishing topic , Then where do I need to , Where to use the topic handle publish Just fine .

2.2 Customize messages or services

For adding custom messages

• CmakeList.txt pass the civil examinations 41 Line modification and addition .h file （ So you can read h The file ）, As shown below ：

  file(GLOB_RECURSE QT_MOC RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} FOLLOW_SYMLINKS include/manipulator_app/*.hpp *.h)
  

• Then compile , In the workspace build Found the compiled .h The header file （ This is msg or srv After compiling ）

• Put the compiled into .h Files in include

• And then in qnode.hpp Reference header file in , It can be used normally

  #include "../myMsg/SyncSetPosition.h"
  #include "../mySrv/SyncGetPosition.h"
  

03 Subscribe to images and display

3.1 Overall process ：

• The main problem here is that the subscribed image is converted to QImage Can be in Qt It shows that , To QImage The function of is as follows ：

  QImage QNode::Mat2QImage(cv::Mat const& src)
  {
        
    QImage dest(src.cols, src.rows, QImage::Format_ARGB32);
  
    const float scale = 255.0;
  
    if (src.depth() == CV_8U) {
        
      if (src.channels() == 1) {
        
        for (int i = 0; i < src.rows; ++i) {
        
          for (int j = 0; j < src.cols; ++j) {
        
            int level = src.at<quint8>(i, j);
            dest.setPixel(j, i, qRgb(level, level, level));
          }
        }
      } else if (src.channels() == 3) {
        
        for (int i = 0; i < src.rows; ++i) {
        
          for (int j = 0; j < src.cols; ++j) {
        
            cv::Vec3b bgr = src.at<cv::Vec3b>(i, j);
            dest.setPixel(j, i, qRgb(bgr[2], bgr[1], bgr[0]));
          }
        }
      }
    } else if (src.depth() == CV_32F) {
        
      if (src.channels() == 1) {
        
        for (int i = 0; i < src.rows; ++i) {
        
          for (int j = 0; j < src.cols; ++j) {
        
            int level = scale * src.at<float>(i, j);
            dest.setPixel(j, i, qRgb(level, level, level));
          }
        }
      } else if (src.channels() == 3) {
        
        for (int i = 0; i < src.rows; ++i) {
        
          for (int j = 0; j < src.cols; ++j) {
        
            cv::Vec3f bgr = scale * src.at<cv::Vec3f>(i, j);
            dest.setPixel(j, i, qRgb(bgr[2], bgr[1], bgr[0]));
          }
        }
      }
    }
  
    return dest;
  }
  

3.2 Problems encountered and solutions

• problem ： The color displayed is very strange , Human skin is blue , Like Avatar
• solve ： Yes to QImage There was a problem , swap R Channels and B Just the passage