Declaration of function and use it



  • Hello there
    i am new in qt working with opencv with qt tool.
    i am creating gui for image processing in qt tool.
    i need to define function and use it with my push button.
    how can i do it.
    please tell me
    waiting



  • Do you mean like this:

    ReturnType ClassName::nameOfFunction (ParameterType parameter){
    // What the function should do
    }


  • Moderators

    @gauravsharma0190 Do you mean you need a function which is called when you press a button?
    If so then please read the documentation: http://doc.qt.io/qt-5.7/signalsandslots.html



  • Dear sir,
    i have a function static void onTrackball(int, void*)
    and its defination.
    i declare it in mainwindow.h as private.
    and in mainwindow i declare it as void Mainwindow::onTrackball(int,void*)
    but error occurs.
    it doesn't build.


  • Moderators

    @gauravsharma0190 Can you post your code and the error message? Else we cannot help you.
    One note onTrackball should not be static if you want to use it as slot.
    Another note: if onTrackball is a slot for QPushButton::clicked() signal then you have to remove the parameters, because clicked() signal does not have any parameters.



  • Thanks for kind reply sir
    here is the code i am sending you.

    #include "opencv2/imgproc/imgproc.hpp"
    #include "opencv2/highgui/highgui.hpp"
    #include <stdlib.h>
    #include <stdio.h>
    
    using namespace cv;
    
    /// Global variables
    
    Mat src, src_gray;
    Mat dst, detected_edges;
    
    int edgeThresh = 1;
    int lowThreshold;
    int const max_lowThreshold = 100;
    int ratio = 3;
    int kernel_size = 3;
    char* window_name = "Edge Map";
    
    /**
     * @function CannyThreshold
     * @brief Trackbar callback - Canny thresholds input with a ratio 1:3
     */
    void CannyThreshold(int, void*)
    {
      /// Reduce noise with a kernel 3x3
      blur( src_gray, detected_edges, Size(3,3) );
    
      /// Canny detector
      Canny( detected_edges, detected_edges, lowThreshold, lowThreshold*ratio, kernel_size );
    
      /// Using Canny's output as a mask, we display our result
      dst = Scalar::all(0);
    
      src.copyTo( dst, detected_edges);
      imshow( window_name, dst );
     }
    
    
    /** @function main */
    int main( int argc, char** argv )
    {
      /// Load an image
      src = imread( argv[1] );
    
      if( !src.data )
      { return -1; }
    
      /// Create a matrix of the same type and size as src (for dst)
      dst.create( src.size(), src.type() );
    
      /// Convert the image to grayscale
      cvtColor( src, src_gray, CV_BGR2GRAY );
    
      /// Create a window
      namedWindow( window_name, CV_WINDOW_AUTOSIZE );
    
      /// Create a Trackbar for user to enter threshold
      createTrackbar( "Min Threshold:", window_name, &lowThreshold, max_lowThreshold, CannyThreshold );
    
      /// Show the image
      CannyThreshold(0, 0);
    
      /// Wait until user exit program by pressing a key
      waitKey(0);
    
      return 0;
    }
    

    in that i want to make as when button is pressed this code and function will run.
    But i don't know where to declare function and how to call it in qt.
    When i declare function void on track ball(int void*) in mainwindow.h
    and define as void mainwindow::ontrackball(int,void*) and build it following outcome
    declaration of 'void mainwindow::ontrackball(int void) outside class is not definition
    expected unqulified-id before '{' token.

    [Edit: Added code formatting tags. ~kshegunov]



  • hey i done that but after build it says declaration of function outside of class is not defination.


  • Moderators

    @gauravsharma0190 Can you please post the code which causes the compiler error? The code you posted is not of interest. Where is mainwindow::ontrackball? Please post mainwindow.h and mainwindow.cpp.


  • Moderators

    @gauravsharma0190 Did you put void on_track_ball(int void*) inside mainwindow class in mainwindow.h? The error message sounds like you put it outside of mainwindow. It should be like:

    // mainwindow.h
    class mainwindow
    {
    private:
        void on_track_ball(int, void*);
    }
    
    // mainwindow.cpp
    void mainwindow::on_track_ball(int, void*)
    {
    }
    

  • Moderators

    @gauravsharma0190 The code you posted does not use Qt as far as I can see. You will need to change more if you want to use Qt.



  • @jsulm
    Yes i did the same but error occurs.
    i couldnt find where is problem


  • Moderators

    @gauravsharma0190 That's why I'm asking for the code! Without it I cannot find the problem as well.



  • So please tell me what i send you sir.
    i give you my all the code .
    Now please tell me only that how to invoke code when i click the button


  • Moderators

    @gauravsharma0190 I already said that: mainwindow.h and mainwindow.cpp
    I provided you a link where you can learn how signals and slots in Qt work, here it is again: http://doc.qt.io/qt-5.7/signalsandslots.html
    Please read it! Else you will not be able to use Qt much - signals/slots is one of the most important concepts in Qt.
    Short description: QPushButton has a signal clicked() (see http://doc.qt.io/qt-5/qabstractbutton.html#clicked). This signal is emitted when user presses the button. You need to connect a slot to that signal, then this slot will be called when you press the button.


  • Moderators

    @gauravsharma0190 A small example application with a button:

    // main.cpp
    #include "mainwindow.h"
    #include <QApplication>
    
    int main(int argc, char *argv[])
    {
        QApplication a(argc, argv);
        MainWindow w;
        w.show();
    
        return a.exec();
    }
    
    // mainwindow.h
    #ifndef MAINWINDOW_H
    #define MAINWINDOW_H
    
    #include <QMainWindow>
    
    namespace Ui {
    class MainWindow;
    }
    
    class MainWindow : public QMainWindow
    {
        Q_OBJECT
    
    public:
        explicit MainWindow(QWidget *parent = 0);
        ~MainWindow();
    
    private slots:
        void doSomethingWhenButtonPressed(bool);
    
    private:
        Ui::MainWindow *ui;
    };
    
    #endif // MAINWINDOW_H
    
    // mainwindow.cpp
    #include "mainwindow.h"
    #include "ui_mainwindow.h"
    
    #include <QDebug>
    
    MainWindow::MainWindow(QWidget *parent) :
        QMainWindow(parent),
        ui(new Ui::MainWindow)
    {
        ui->setupUi(this);
    
        connect(ui->pushButton, SIGNAL(clicked(bool)), this, SLOT(doSomethingWhenButtonPressed(bool)));
    }
    
    MainWindow::~MainWindow()
    {
        delete ui;
    }
    
    void MainWindow::doSomethingWhenButtonPressed(bool)
    {
        qDebug() << "Button pressed!";
    }


  • @jsulm
    i got it tht how to use push button.
    using connect i know it because i did it with my code.
    but i want to know how to declare and defination of function in qt and use these in pushbutton.
    Like we do in c as declare and defination of function and use it main()
    as in c++ declare and defination and use it in main function or classes.
    please give me a simple example or link.

    like


  • Moderators

    @gauravsharma0190 I don't understand the problem. Qt is not a programming language. You use C++ with qt. So you define and use your function/method as any other function/method in C++.
    I already gave you an example showing how to use a push button to execute a method when the button is clicked. Isn't that what you want to do?
    Please explain what is the problem! Maybe some code?


  • Qt Champions 2017

    @gauravsharma0190

    Hi
    As @jsulm says, its a bit unclear what you ask.
    You can use functions just like you would in c, but in c++ gui program,
    normally main is the not the center of the application. QMainwindow is or some other class.
    Maybe this helps:

    //--------------------
    //std c program
    //--------------------
    void myfunc() {};
    
    void main() {
      myfunc();
    }
    
    //--------------------
    //c++ function being a class member ( lives in class)
    //--------------------
    class Mainwindow {
     public:
      void myfunc();
    };
    (in cpp)
    Mainwindow::myfunc() {
      //code
    }
    //--------------------
    //c++ with "outside" function ( non member function)
    //--------------------
    (in .h)
    void outsidefunc(); // define
    
    class Mainwindow {
     public:
      void myfunc();
    };
    (in cpp)
    
    void outsidefunc() { // implement
    }
    
    Mainwindow::myfunc() {
      outsidefunc();
    }
    


  • Yes sir see i have a c code of opencv which process the image.
    Now my problem is i want to use this code with qt as when button is pressed my push button calls the function of that C code in which main part of Process is defined.
    Here is the C code.
    #include "opencv2/imgproc/imgproc.hpp"
    #include "opencv2/highgui/highgui.hpp"
    #include <stdlib.h>
    #include <stdio.h>

    using namespace cv;

    /// Global variables

    Mat src, src_gray;
    Mat dst, detected_edges;

    int edgeThresh = 1;
    int lowThreshold;
    int const max_lowThreshold = 100;
    int ratio = 3;
    int kernel_size = 3;
    char* window_name = "Edge Map";

    /**

    • @function CannyThreshold
    • @brief Trackbar callback - Canny thresholds input with a ratio 1:3
      /
      void CannyThreshold(int, void
      )
      {
      /// Reduce noise with a kernel 3x3
      blur( src_gray, detected_edges, Size(3,3) );

    /// Canny detector
    Canny( detected_edges, detected_edges, lowThreshold, lowThreshold*ratio, kernel_size );

    /// Using Canny's output as a mask, we display our result
    dst = Scalar::all(0);

    src.copyTo( dst, detected_edges);
    imshow( window_name, dst );
    }

    /** @function main /
    int main( int argc, char
    * argv )
    {
    /// Load an image
    src = imread( argv[1] );

    if( !src.data )
    { return -1; }

    /// Create a matrix of the same type and size as src (for dst)
    dst.create( src.size(), src.type() );

    /// Convert the image to grayscale
    cvtColor( src, src_gray, CV_BGR2GRAY );

    /// Create a window
    namedWindow( window_name, CV_WINDOW_AUTOSIZE );

    /// Create a Trackbar for user to enter threshold
    createTrackbar( "Min Threshold:", window_name, &lowThreshold, max_lowThreshold, CannyThreshold );

    /// Show the image
    CannyThreshold(0, 0);

    /// Wait until user exit program by pressing a key
    waitKey(0);

    return 0;
    }
    Now i make a Push button Name Process_image in MainWindow.ui and connect to slot as clicked() by right clicking of mouse.
    here comes the slot to mainwindow.cpp
    void mainwidow::Process_image_clicke()
    {
    }
    Now i don't understand how to make function of my C code and use it in Pusebutton.


  • Qt Champions 2017

    well you should make a pair of .h and .cpp files for the opencv stuff
    lets call it myopenvc.h and myopenvc.cpp

    in h. you can declare the function u want rest of program to use

    void setupOPENVC();

    and in .cpp

    void setupOPENVC() {
    // the code from the old c- main. !
    src = imread( argv[1] );
    xxxx
    }

    then in Mainwindow.cpp
    #include "myopencv.h"

    and now u can call your function
    void mainwidow::Process_image_clicke()
    {
    setupOPENVC();
    }

    ps:
    In event driven programs. ( like Qt)
    stuff like
    waitKey(0);
    or FOREVER loops are not to be used as it
    will freeze the program and it stops working.



  • @mrjj Hello i did it sir.
    but error occurs.



  • @jsulm Yes sir see i have a c code of opencv which process the image.
    Now my problem is i want to use this code with qt as when button is pressed my push button calls the function of that C code in which main part of Process is defined.
    Here is the C code.
    #include "opencv2/imgproc/imgproc.hpp"
    #include "opencv2/highgui/highgui.hpp"
    #include <stdlib.h>
    #include <stdio.h>

    using namespace cv;

    /// Global variables

    Mat src, src_gray;
    Mat dst, detected_edges;

    int edgeThresh = 1;
    int lowThreshold;
    int const max_lowThreshold = 100;
    int ratio = 3;
    int kernel_size = 3;
    char* window_name = "Edge Map";

    /**

    @function CannyThreshold
    @brief Trackbar callback - Canny thresholds input with a ratio 1:3
    /
    void CannyThreshold(int, void)
    {
    /// Reduce noise with a kernel 3x3
    blur( src_gray, detected_edges, Size(3,3) );
    /// Canny detector
    Canny( detected_edges, detected_edges, lowThreshold, lowThreshold*ratio, kernel_size );

    /// Using Canny's output as a mask, we display our result
    dst = Scalar::all(0);

    src.copyTo( dst, detected_edges);
    imshow( window_name, dst );
    }

    /** @function main /
    int main( int argc, char* argv )
    {
    /// Load an image
    src = imread( argv[1] );

    if( !src.data )
    { return -1; }

    /// Create a matrix of the same type and size as src (for dst)
    dst.create( src.size(), src.type() );

    /// Convert the image to grayscale
    cvtColor( src, src_gray, CV_BGR2GRAY );

    /// Create a window
    namedWindow( window_name, CV_WINDOW_AUTOSIZE );

    /// Create a Trackbar for user to enter threshold
    createTrackbar( "Min Threshold:", window_name, &lowThreshold, max_lowThreshold, CannyThreshold );

    /// Show the image
    CannyThreshold(0, 0);

    /// Wait until user exit program by pressing a key
    waitKey(0);

    return 0;
    }
    Now i make a Push button Name Process_image in MainWindow.ui and connect to slot as clicked() by right clicking of mouse.
    here comes the slot to mainwindow.cpp
    void mainwidow::Process_image_clicke()
    {
    }
    Now i don't understand how to make function of my C code and use it in Pusebutton.


  • Moderators

    @gauravsharma0190 Well, you can put that C code in

    void mainwidow::Process_image_clicke()
    {
        // Put C code here
    }
    

    But I'm not sure whether you should remove waitKey(0); as it could be problematic in a Qt program.



  • @jsulm
    i put it into Process_image_click()
    {
    //code
    }
    but error occurs.
    as ontrackball function not declare


  • Moderators

    @gauravsharma0190 What is ontrackball? Where is it declared? Do you have to include a header file where it is declared?



  • Yes it is function which is declare in the Opencv C code.
    Here is the function.
    @brief Trackbar callback - Canny thresholds input with a ratio 1:3
    /
    void onTrackball(int, void)
    {
    /// Reduce noise with a kernel 3x3
    blur( src_gray, detected_edges, Size(3,3) );
    /// Canny detector
    Canny( detected_edges, detected_edges, lowThreshold, lowThreshold*ratio, kernel_size );

    /// Using Canny's output as a mask, we display our result
    dst = Scalar::all(0);

    src.copyTo( dst, detected_edges);
    imshow( window_name, dst );
    }



  • @jsulm Yes it is function which is declare in the Opencv C code.
    Here is the function.
    @brief Trackbar callback - Canny thresholds input with a ratio 1:3
    /
    void onTrackball(int, void)
    {
    /// Reduce noise with a kernel 3x3
    blur( src_gray, detected_edges, Size(3,3) );
    /// Canny detector
    Canny( detected_edges, detected_edges, lowThreshold, lowThreshold*ratio, kernel_size );

    /// Using Canny's output as a mask, we display our result
    dst = Scalar::all(0);

    src.copyTo( dst, detected_edges);
    imshow( window_name, dst );
    }

    less than a minute ago


  • Moderators

    @gauravsharma0190 Where is this function declared? In which header file? "function not declared" means the function is not known. You have to make it visible including the header file. It is the same story as in C.



  • @jsulm i Declare it in mainwindow.h
    file as void onTrackball.
    and i will send you all my code which i did .



  • @jsulm
    Here i am sending you my all code.
    **

    • /////main.cpp///**
      #include "mainwindow.h"
      #include <QApplication>
      #include<QSplashScreen>
      #include<QTimer>
      #include<opencv2/highgui/highgui.hpp>
      #include<opencv2/core/core.hpp>
      #include<opencv2/opencv.hpp>
      using namespace cv;
      using namespace std;
      int main(int argc, char *argv[])
      {

      QApplication a(argc, argv);
      QSplashScreen *splash =new QSplashScreen;
      splash->setPixmap(QPixmap("/home/pi/Desktop/ceeri1.jpg"));
      splash->show();

      MainWindow w;
      QTimer::singleShot(3500,splash,SLOT(close()));

      QTimer::singleShot(3500,&w,SLOT(show()));

      //w.show();

      return a.exec();
      }
      ////mainwindow.h
      #ifndef MAINWINDOW_H
      #define MAINWINDOW_H

    #include <QMainWindow>
    //using namespace cv;
    namespace Ui {
    class MainWindow;
    }

    class MainWindow : public QMainWindow
    {
    Q_OBJECT

    public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

    private slots:
    void showTime();

    void on_pushButton_5_clicked();
    

    void onTrackball_clicked(int,void*);

    private:
    Ui::MainWindow *ui;
    };

    #endif // MAINWINDOW_H
    ///mainwindow.c

    #include "mainwindow.h"
    #include "ui_mainwindow.h"
    #include<opencv2/opencv.hpp>
    #include <opencv2/highgui/highgui.hpp>
    #include <opencv2/core/core.hpp>
    #include<QFileDialog>
    #include<QMessageBox>
    #include <iostream>
    #include <string>
    #include <fstream>
    #include<time.h>
    #include<QTimer>
    #include<QDateTime>
    using namespace cv;
    using namespace std;
    MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
    {
    ui->setupUi(this);
    QTimer *timer=new QTimer(this);
    connect(timer,SIGNAL(timeout()),this,SLOT(showTime()));
    timer->start();
    QDateTime dateTime=QDateTime::currentDateTime();
    QString datetimetext=dateTime.toString();
    ui->DateTime->setText(datetimetext);

    }
    ////////Time///////////////
    void MainWindow:: showTime()
    {
    QTime time=QTime::currentTime();
    QString time_text=time.toString("hh : mm : ss");
    if((time.second() % 2)==0)
    {
    time_text[3] =' ';
    time_text[8] =' ';
    }
    ui->Digital->setText(time_text);

    }

    MainWindow::~MainWindow()
    {
    delete ui;
    }

    void MainWindow::on_pushButton_4_clicked()
    {

    }

    void MainWindow::on_pushButton_5_clicked()
    {
    QString filename=QFileDialog::getOpenFileName(
    this,
    tr("Open file") ,
    "/home/pi/Desktop",
    tr("All files(*.png *.jpg)"));

    QMessageBox::information(this,tr("Filename"),filename);
    if(QString::compare(filename,QString())!=0)
    {
        QImage image;
        bool valid=image.load(filename);
        if(valid)
        {
            image=image.scaledToWidth(ui->Picture->width(),Qt::SmoothTransformation);
            ui->Picture->setPixmap(QPixmap::fromImage(image));
    
        }
    

    void MainWindow::onTrackball_clicked(int,void*)
    {
    //Here wite the all function//
    ///Now how to put this code in this.

    ////////This is the code i have to input in this push button////
    Mat src, src_gray;
    Mat dst, detected_edges;

    int edgeThresh = 1;
    int lowThreshold;
    int const max_lowThreshold = 100;
    int ratio = 3;
    int kernel_size = 3;
    char* window_name = "Edge Map";

    /**

    @function CannyThreshold
    @brief Trackbar callback - Canny thresholds input with a ratio 1:3
    /
    void CannyThreshold(int, void)
    {
    /// Reduce noise with a kernel 3x3
    blur( src_gray, detected_edges, Size(3,3) );
    /// Canny detector
    Canny( detected_edges, detected_edges, lowThreshold, lowThreshold*ratio, kernel_size );

    /// Using Canny's output as a mask, we display our result
    dst = Scalar::all(0);

    src.copyTo( dst, detected_edges);
    imshow( window_name, dst );
    }

    /** @function main /
    int main( int argc, char* argv )
    {
    /// Load an image
    src = imread( argv[1] );

    if( !src.data )
    { return -1; }

    /// Create a matrix of the same type and size as src (for dst)
    dst.create( src.size(), src.type() );

    /// Convert the image to grayscale
    cvtColor( src, src_gray, CV_BGR2GRAY );

    /// Create a window
    namedWindow( window_name, CV_WINDOW_AUTOSIZE );

    /// Create a Trackbar for user to enter threshold
    createTrackbar( "Min Threshold:", window_name, &lowThreshold, max_lowThreshold, CannyThreshold );

    /// Show the image
    CannyThreshold(0, 0);

    /// Wait until user exit program by pressing a key
    waitKey(0);

    return 0;
    }

    }
    }

  • Moderators

    Sorry, but the code you posted is invalid C/C++! First of all: why do you have 2 main functions?
    Why did you put other functions inside void MainWindow::onTrackball_clicked(int,void*)? This is not going to compile and I'm not going to fix it for you. How familiar are you actually with C/C++?
    What you have to do is: do not put the C function definitions inside void MainWindow::onTrackball_clicked(int,void*), instead put them inside another source code file and header, include the header file in MainWindow and then call the functions in void MainWindow::onTrackball_clicked(int,void*). As an alternative you can have those C functions in MainWindow.cpp but not inside void MainWindow::onTrackball_clicked(int,void*) !



  • @jsulm
    i don't put these function definition inside voidmainwindow::ontrackball
    but i am asking you how can i call that function inside my void mainwindow::ontrackball

    void CannyThreshold(int, void)
    {
    /// Reduce noise with a kernel 3x3
    blur( src_gray, detected_edges, Size(3,3) );
    /// Canny detector
    Canny( detected_edges, detected_edges, lowThreshold, lowThreshold*ratio, kernel_size );
    
    /// Using Canny's output as a mask, we display our result
    dst = Scalar::all(0);
    
    src.copyTo( dst, detected_edges);
    imshow( window_name, dst );
    }
    

    Mean i hyave done .cpp and .h file of this and include in my code both.


  • Moderators

    @gauravsharma0190 Like this?

    CannyThreshold(1, nullptr);
    

    So, what exactly is the problem?
    In the code you posted you DID put these function definitions inside void MainWindow::onTrackball_clicked(int,void*) (just check what you posted).


  • Moderators

    @gauravsharma0190 Shouldn't

    void CannyThreshold(int, void)
    

    be

    void CannyThreshold(int, void*)
    

    ?



  • ok now i will send you refresh code just wait.
    Thank you.
    i will send you refresh code and errors.



  • @jsulm
    hey here is the code i have done with that.
    /////main.cpp////

    #include<opencv2/highgui/highgui.hpp>
    #include<opencv2/core/core.hpp>
    #include<opencv2/opencv.hpp>
    using namespace cv;
    using namespace std;
    int main(int argc, char *argv[])
    {
    
        QApplication a(argc, argv);
        QSplashScreen *splash =new QSplashScreen;
        splash->setPixmap(QPixmap("/home/pi/Desktop/ceeri1.jpg"));
        splash->show();
    
        MainWindow w;
        QTimer::singleShot(3500,splash,SLOT(close()));
    
        QTimer::singleShot(3500,&w,SLOT(show()));
    
      //w.show();
    
        return a.exec();
    }
    

    ///mainwindow.h///

    #ifndef MAINWINDOW_H
    #define MAINWINDOW_H
    
    #include <QMainWindow>
    //using namespace cv;
    namespace Ui {
    class MainWindow;
    }
    
    class MainWindow : public QMainWindow
    {
    Q_OBJECT
    
    public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    
    private slots:
    void showTime();
    
    void on_pushButton_5_clicked();
    void onTrackball_clicked(int,void*);
    
    private:
    Ui::MainWindow *ui;
    };
    
    #endif // MAINWINDOW_H
    

    ///ontrack.h///

    #ifndef __ONTRACK_h
    #define __ONTRACK_h
    void cannyThresold(int,void*);
    #endif
    

    ///ontrack.cpp

    #include "ontrack.h"
    #include<opencv2/opencv.hpp>
    #include <opencv2/highgui/highgui.hpp>
    #include <opencv2/core/core.hpp>
    void CannyThreshold(int, void)
    {
    /// Reduce noise with a kernel 3x3
    blur( src_gray, detected_edges, Size(3,3) );
    /// Canny detector
    Canny( detected_edges, detected_edges, lowThreshold, lowThreshold*ratio, kernel_size );
    
    /// Using Canny's output as a mask, we display our result
    dst = Scalar::all(0);
    
    src.copyTo( dst, detected_edges);
    imshow( window_name, dst );
    }
    

    //Here Comes Mainwindow.cpp///

    #include "ui_mainwindow.h"
    #include<opencv2/opencv.hpp>
    #include <opencv2/highgui/highgui.hpp>
    #include <opencv2/core/core.hpp>
    #include "ontrack.h"
    #include<QFileDialog>
    #include<QMessageBox>
    #include <iostream>
    #include <string>
    #include <fstream>
    #include<time.h>
    #include<QTimer>
    #include<QDateTime>
    using namespace cv;
    using namespace std;
    MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
    {
    ui->setupUi(this);
    QTimer *timer=new QTimer(this);
    connect(timer,SIGNAL(timeout()),this,SLOT(showTime()));
    timer->start();
    QDateTime dateTime=QDateTime::currentDateTime();
    QString datetimetext=dateTime.toString();
    ui->DateTime->setText(datetimetext);
    
    }
    ////////Time///////////////
    void MainWindow:: showTime()
    {
    QTime time=QTime::currentTime();
    QString time_text=time.toString("hh : mm : ss");
    if((time.second() % 2)==0)
    {
    time_text[3] =' ';
    time_text[8] =' ';
    }
    ui->Digital->setText(time_text);
    
    }
    
    MainWindow::~MainWindow()
    {
    delete ui;
    }
    
    void MainWindow::on_pushButton_4_clicked()
    {
    
    }
    
    void MainWindow::on_pushButton_5_clicked()
    {
    QString filename=QFileDialog::getOpenFileName(
    this,
    tr("Open file") ,
    "/home/pi/Desktop",
    tr("All files(*.png *.jpg)"));
    
    QMessageBox::information(this,tr("Filename"),filename);
    if(QString::compare(filename,QString())!=0)
    {
        QImage image;
        bool valid=image.load(filename);
        if(valid)
        {
            image=image.scaledToWidth(ui->Picture->width(),Qt::SmoothTransformation);
            ui->Picture->setPixmap(QPixmap::fromImage(image));
    
        }
    void MainWindow::onTrackball_clicked(int,void*)
    {
    
    
    Mat src, src_gray;
    Mat dst, detected_edges;
    
    int edgeThresh = 1;
    int lowThreshold;
    int const max_lowThreshold = 100;
    int ratio = 3;
    int kernel_size = 3;
    char* window_name = "Edge Map";
    
    
    
    @function CannyThreshold
    @brief Trackbar callback - Canny thresholds input with a ratio 1:3
    /
    
    
    /// Load an image
    src = imread( argv[1] );
    
    if( !src.data )
    { return -1; }
    
    /// Create a matrix of the same type and size as src (for dst)
    dst.create( src.size(), src.type() );
    
    /// Convert the image to grayscale
    cvtColor( src, src_gray, CV_BGR2GRAY );
    
    /// Create a window
    namedWindow( window_name, CV_WINDOW_AUTOSIZE );
    
    /// Create a Trackbar for user to enter threshold
    createTrackbar( "Min Threshold:", window_name, &lowThreshold, max_lowThreshold, CannyThreshold );
    
    /// Show the image
    CannyThreshold(0, 0);
    
    }
    }
    ...
    But error occurs defination of function outside the class.


  • @gauravsharma0190 said:

    Sorry in ontrack.cpp i again add
    Mat src, src_gray;
    Mat dst, detected_edges;


  • Moderators

    @gauravsharma0190 Can you post the whole error message?
    Why do you have int and void* parameter in onTrackball_clicked which you do not use?


  • Moderators

    @gauravsharma0190 Take a look at this:

    
    void MainWindow::on_pushButton_5_clicked()
    {
    QString filename=QFileDialog::getOpenFileName(
    this,
    tr("Open file") ,
    "/home/pi/Desktop",
    tr("All files(*.png *.jpg)"));
    
    QMessageBox::information(this,tr("Filename"),filename);
    if(QString::compare(filename,QString())!=0)
    {
        QImage image;
        bool valid=image.load(filename);
        if(valid)
        {
            image=image.scaledToWidth(ui->Picture->width(),Qt::SmoothTransformation);
            ui->Picture->setPixmap(QPixmap::fromImage(image));
    
        }
    void MainWindow::onTrackball_clicked(int,void*)
    {
    

    void MainWindow::onTrackball_clicked(int,void*) is inside void MainWindow::on_pushButton_5_clicked() - this is invalid!



  • @jsulm
    but i am not defining ontrack_clicked in push button its different.


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