Publishing video file and images with ROS

If you have video/image file on your disk and you want to publish it without coding, you can use the following nodes:

Publishing Images

Here are some examples to publish an image:

rosrun image_publisher image_publisher <path_to_image_file>

1	rosrun image_publisher image_publisher <path_to_image_file>

And more Advanced launch file:

<!--
Example of run:
roslaunch image_publisher.launch image_file:=image.png
-->
<launch>

<arg name="image_file" default="/opt/ros/kinetic/share/turtlesim/images/kinetic.png" />
<node pkg="image_publisher" type="image_publisher" name="image_publisher" args="$(arg image_file)">
<param name="frame_id" value="camera_frame" />
<param name="publish_rate" value="1" />
<param name="camera_info_url" value="file:///$(env HOME)/.ros/camera_info/camera.yaml" />
</node>
</launch>

<!--

Example of run:

roslaunch image_publisher.launch image_file:=image.png

-->

</node>

</launch>

Publishing Videos

Camera Calibration Based on Zhang’s Algorithm (Chess Board) Explained

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Camera Calibration Based on Direct Linear Transform Explained

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Geometry of Stereo Vision explained

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In this video, I explain the geometry of stereo Vision. Please have look at my other tutorial about finding the essential and fundamental matrix.

The relation between the size of an object and its projection in camera fame

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What is the relation between the size of an object and its projection in camera fame? In this video, I explain how far you should stay from an object to see it at your desired size at camera frame

Vanishing points in computer vision explained

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In this tutorial, I explain the vanishing points in computer vision.

Equation of Line and Plane in 3D Space Explained

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The equation of Line and plane in 3D Space:

How to develop GUI Application with PyQt (python Qt)

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There are two main methods for developing GUI application with qt:
1) Adding all widgets in your code (your cpp or python code)
2) Creating qt UI files, adding widgets there and load everything into your application.

1)Adding all widgets in your code

Here is the snippet for adding all widgets and their slots in code:

import sys
print(sys.version)
import warnings
warnings.filterwarnings('ignore')


from PyQt5 import QtCore, QtWidgets
from PyQt5.QtWidgets import QMainWindow, QLabel, QSlider
from PyQt5.QtCore import QSize, Qt, pyqtSlot,pyqtSignal 



class HelloWindow(QMainWindow):
    
    pushButtonClicked = pyqtSignal()
    valueUpdating = pyqtSignal(int)
    
    
    def pushButtonClicked(self):
        self.title.setText("PyQt updated!")
            
    def valueUpdating(self, value):
        self.title.setText(str(value))
    
    def __init__(self):
        QMainWindow.__init__(self)

        self.setMinimumSize(QSize(640, 480))    
        self.setWindowTitle("Hello world") 

        self.title = QLabel("PyQt!", self)
        self.title.setAlignment(QtCore.Qt.AlignCenter) 


        self.pushButton = QtWidgets.QPushButton(self)
        self.pushButton.setGeometry(QtCore.QRect(140, 200, 99, 27))#x,y, width, height
        self.pushButton.setObjectName("pushButton")
        self.pushButton.setText("Click Me!")
        self.pushButton.clicked.connect(self.pushButtonClicked)
        
        self.slider = QtWidgets.QSlider(self)
        self.slider.setGeometry(QtCore.QRect(100, 20, 100, 30))
        self.slider.setFocusPolicy(Qt.StrongFocus)
        self.slider.setTickPosition(QSlider.TicksBothSides)
        self.slider.setSingleStep(1)
        self.slider.setPageStep(1)
        self.slider.setMaximum(100)
        self.slider.setMinimum(0)
        self.slider.setOrientation(Qt.Horizontal)
        
        self.slider.valueChanged.connect(self.valueUpdating)
        


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    mainWin = HelloWindow()
    mainWin.show()
    sys.exit( app.exec_() )

import sys

print(sys.version)

import warnings

warnings.filterwarnings('ignore')

from PyQt5 import QtCore, QtWidgets

from PyQt5.QtWidgets import QMainWindow, QLabel, QSlider

from PyQt5.QtCore import QSize, Qt, pyqtSlot,pyqtSignal

class HelloWindow(QMainWindow):

pushButtonClicked = pyqtSignal()

valueUpdating = pyqtSignal(int)

def pushButtonClicked(self):

self.title.setText("PyQt updated!")

def valueUpdating(self, value):

self.title.setText(str(value))

def __init__(self):

QMainWindow.__init__(self)

self.setMinimumSize(QSize(640, 480))

self.setWindowTitle("Hello world")

self.title = QLabel("PyQt!", self)

self.title.setAlignment(QtCore.Qt.AlignCenter)

self.pushButton = QtWidgets.QPushButton(self)

self.pushButton.setGeometry(QtCore.QRect(140, 200, 99, 27))#x,y, width, height

self.pushButton.setObjectName("pushButton")

self.pushButton.setText("Click Me!")

self.pushButton.clicked.connect(self.pushButtonClicked)

self.slider = QtWidgets.QSlider(self)

self.slider.setGeometry(QtCore.QRect(100, 20, 100, 30))

self.slider.setFocusPolicy(Qt.StrongFocus)

self.slider.setTickPosition(QSlider.TicksBothSides)

self.slider.setSingleStep(1)

self.slider.setPageStep(1)

self.slider.setMaximum(100)

self.slider.setMinimum(0)

self.slider.setOrientation(Qt.Horizontal)

self.slider.valueChanged.connect(self.valueUpdating)

if __name__ == "__main__":

app = QtWidgets.QApplication(sys.argv)

mainWin = HelloWindow()

mainWin.show()

sys.exit( app.exec_() )

2) Creating qt UI files, adding widgets there and load everything into your application

Now let’s do what we have done in the first method in a UI file and load it. First, create a text file and put the followings in it and save it as “mainwindow.ui”

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>617</width>
    <height>419</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QPushButton" name="pushButton">
    <property name="geometry">
     <rect>
      <x>200</x>
      <y>120</y>
      <width>99</width>
      <height>27</height>
     </rect>
    </property>
    <property name="text">
     <string>PushButton</string>
    </property>
   </widget>
   <widget class="QLabel" name="title">
    <property name="geometry">
     <rect>
      <x>60</x>
      <y>30</y>
      <width>67</width>
      <height>17</height>
     </rect>
    </property>
    <property name="text">
     <string>PyQt!</string>
    </property>
   </widget>
   <widget class="QSlider" name="slider">
    <property name="geometry">
     <rect>
      <x>190</x>
      <y>30</y>
      <width>160</width>
      <height>29</height>
     </rect>
    </property>
    <property name="orientation">
     <enum>Qt::Horizontal</enum>
    </property>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>617</width>
     <height>25</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

<?xml version="1.0" encoding="UTF-8"?>

<class>MainWindow</class>

<rect>

</rect>

</property>

<string>MainWindow</string>

</property>

<rect>

</rect>

</property>

<string>PushButton</string>

</property>

</widget>

<rect>

</rect>

</property>

</property>

</widget>

<rect>

</rect>

</property>

<enum>Qt::Horizontal</enum>

</property>

</widget>

<rect>

</rect>

</property>

</widget>

</widget>

</ui>

Now call it in your python file like this:

import sys
print(sys.version)
import warnings
warnings.filterwarnings('ignore')


from PyQt5 import QtCore, QtWidgets
from PyQt5.QtWidgets import QMainWindow, QLabel, QSlider
from PyQt5.QtCore import QSize, Qt, pyqtSlot,pyqtSignal 
from PyQt5.uic import loadUi


class HelloWindow(QMainWindow):
    
    pushButtonClicked = pyqtSignal()
    valueUpdating = pyqtSignal(int)
    
    
    def pushButtonClicked(self):
        self.title.setText("PyQt updated!")
            
    def valueUpdating(self, value):
        self.title.setText(str(value))
    
    def __init__(self):
        QMainWindow.__init__(self)

        self.setMinimumSize(QSize(640, 480))    
        self.setWindowTitle("Hello world")
        loadUi('mainwindow.ui',self)
        self.pushButton.clicked.connect(self.pushButtonClicked)
        self.slider.valueChanged.connect(self.valueUpdating)

if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    mainWin = HelloWindow()
    mainWin.show()
    sys.exit( app.exec_() )

import sys

print(sys.version)

import warnings

warnings.filterwarnings('ignore')

from PyQt5 import QtCore, QtWidgets

from PyQt5.QtWidgets import QMainWindow, QLabel, QSlider

from PyQt5.QtCore import QSize, Qt, pyqtSlot,pyqtSignal

from PyQt5.uic import loadUi

class HelloWindow(QMainWindow):

pushButtonClicked = pyqtSignal()

valueUpdating = pyqtSignal(int)

def pushButtonClicked(self):

self.title.setText("PyQt updated!")

def valueUpdating(self, value):

self.title.setText(str(value))

def __init__(self):

QMainWindow.__init__(self)

self.setMinimumSize(QSize(640, 480))

self.setWindowTitle("Hello world")

loadUi('mainwindow.ui',self)

self.pushButton.clicked.connect(self.pushButtonClicked)

self.slider.valueChanged.connect(self.valueUpdating)

if __name__ == "__main__":

app = QtWidgets.QApplication(sys.argv)

mainWin = HelloWindow()

mainWin.show()

sys.exit( app.exec_() )

The results should be the same as what you got in the first method.

Adding Qt UI files to your CMake

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Qt uses qmake to generate classes from UI files and compile everything in the project, luckily there are some macros in CMake that allows you to bring everything into your CMake and build everything there, here is what you need to do:

cmake_minimum_required (VERSION 2.8.12)
project (Qt5CMake)

find_package (Qt5Widgets)

set (MyProjectLib_src ${PROJECT_SOURCE_DIR}/src/mainwindow.cpp)
set (MyProjectLib_hdr ${PROJECT_SOURCE_DIR}/include/mainwindow.h)
set (MyProjectLib_ui  ${PROJECT_SOURCE_DIR}/UI/mainwindow.ui)
set (MyProjectBin_src ${PROJECT_SOURCE_DIR}/src/main.cpp)

qt5_wrap_cpp(MyProjectLib_hdr_moc ${MyProjectLib_hdr})
qt5_wrap_ui (MyProjectLib_ui_moc  ${MyProjectLib_ui})

include_directories (${PROJECT_SOURCE_DIR})
include_directories (${PROJECT_BINARY_DIR})

add_library (MyProjectLib SHARED 
    ${MyProjectLib_src}
    ${MyProjectLib_hdr_moc}
    ${MyProjectLib_ui_moc}
)
target_link_libraries (MyProjectLib Qt5::Widgets)

add_executable(MyProject ${MyProjectBin_src})
target_link_libraries (MyProject MyProjectLib)

cmake_minimum_required (VERSION 2.8.12)

project (Qt5CMake)

find_package (Qt5Widgets)

set (MyProjectLib_src ${PROJECT_SOURCE_DIR}/src/mainwindow.cpp)

set (MyProjectLib_hdr ${PROJECT_SOURCE_DIR}/include/mainwindow.h)

set (MyProjectLib_ui ${PROJECT_SOURCE_DIR}/UI/mainwindow.ui)

set (MyProjectBin_src ${PROJECT_SOURCE_DIR}/src/main.cpp)

qt5_wrap_cpp(MyProjectLib_hdr_moc ${MyProjectLib_hdr})

qt5_wrap_ui (MyProjectLib_ui_moc ${MyProjectLib_ui})

include_directories (${PROJECT_SOURCE_DIR})

include_directories (${PROJECT_BINARY_DIR})

add_library (MyProjectLib SHARED

${MyProjectLib_src}

${MyProjectLib_hdr_moc}

${MyProjectLib_ui_moc}

)

target_link_libraries (MyProjectLib Qt5::Widgets)

add_executable(MyProject ${MyProjectBin_src})

target_link_libraries (MyProject MyProjectLib)

you can find the full project at my Github

Clang format and code beautifier for Qt Creator

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Different developers use different styles with different IDE (i.e some people use space, some use tab) which may cause lots of change in your git repository. One solution to this is to use some standard code formatting and beautifier. clang is a great tool for this purpose and can be easily integrated with git hooks and IDE.
First, install it by:

sudo apt-get install clang-format

1	sudo apt-get install clang-format

now if you have a file like this:

after running the following:

clang-format -style=WebKit -i main.cpp

1	clang-format -style=WebKit -i main.cpp

now you can use it like:

Available styles are LLVM, Google, Chromium, Mozilla, WebKit.

You can config clang for Qt Creator:

go to Tools>Option then:

And then go to the Environment>keyboard and set your shortcut:

This is what I get after pressing shift+s: