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Declaration of function and use it


  • Qt Champions 2018

    @gauravsharma0190 What is Mat and where is it declared?


  • Qt Champions 2018

    @gauravsharma0190 Didn't you forget

    using namespace cv;
    

    in the cpp file?



  • @jsulm
    Mat is basically a class with two data parts: the matrix header (containing information such as the size of the matrix, the method used for storing, at which address is the matrix stored, and so on) and a pointer to the matrix containing the pixel values (taking any dimensionality depending on the method chosen for storing) . The matrix header size is constant, however the size of the matrix itself may vary from image to image and usually is larger by orders of magnitude



  • @gauravsharma0190
    Hey jslum
    thanks very mush i did it without error
    Now new problem arises when i clicked the push button it tells
    The program has unexpectedly finished.
    /home/pi/Desktop/qt /build-Desktop1-GCC Local/Desktop crashed.


  • Qt Champions 2018

    @gauravsharma0190 Most probably it crashes because of an invalid pointer. Debug your application step by step to see where exactly it crashes.



  • @jsulm
    Hello sir
    i debug the programme but when i press button it tells
    the inferior stooped because it receives signal from OS
    Signal name SIGABRT
    Signal mean Aborted.
    Now how to solve it


  • Qt Champions 2018

    @gauravsharma0190 Put a breakpoint in the slot which is called when you press the button and check where exactly it crashes.



  • IT CRASHES WHERE FUNCTION ontrack()
    defination
    Canny(edge, edge, edgeThresh, edgeThresh*3, 3);
    kernel_size issue i think.
    int kernel_size =3;
    here



  • @jsulm
    It crashes when i press the push button .
    I debugged it and found it creshes when my function call.
    Error found->it takes signal from OS.
    Now How to fix it.


  • Qt Champions 2018

    @gauravsharma0190 How to fix what?
    What do you mean by "Error found->it takes signal from OS" - what OS signal do you mean? Do you mean SIGABRT?
    I don't know how to fix it because I have no idea what the problem is. But usually such problems are caused by bugs in applications. You have to check your code and see what is wrong at the line where your application crashes.


  • Qt Champions 2018

    @gauravsharma0190 Can you post the code and mark the line where it crashes?



  • @jsulm
    Mainwindow.cpp

    void MainWindow::on_onTrackball_clicked()
    {
        int threshold_value = 0;
        int threshold_type = 3;
        int const max_value = 255;
        int const max_type = 4;
       // int const max_BINARY_value = 255;
    
        Mat src, src_gray, dst;
      //  char* window_name = "Threshold Demo";
    
        //char* trackbar_type = "Type: \n 0: Binary \n 1: Binary Inverted \n 2: Truncate \n 3: To Zero \n 4: To Zero Inverted";
        //char* trackbar_value = "Value";
    
    
    
    
        /// Load image
        src = imread( "/home/pi/Desktop/b4.jpg");
    
    
          /// Convert the image to Gray
          cvtColor( src, src_gray, CV_BGR2GRAY );
    
          /// Create a window to display results
          namedWindow( "Threshold", CV_WINDOW_AUTOSIZE );
    
          /// Create Trackbar to choose type of Threshold
          createTrackbar( "Type: \n 0: Binary \n 1: Binary Inverted \n 2: Truncate \n 3: To Zero \n 4: To Zero Inverted","Threshold", &threshold_type, max_type, Threshold_Demo );
    
          createTrackbar( "value","Threshold", &threshold_value, max_value, Threshold_Demo );
    
          /// Call the function to initialize
    @@@   ***Threshold_Demo( 0, 0)***
    
    
    }
    

    onTrack.h

    #ifndef ONTRACKBALL_H_
    #define ONTRACKBALL_H_
      void Threshold_Demo( int, void* );
    #endif
    

    ontrack.cpp

    void Threshold_Demo( int, void* )
    {
      /* 0: Binary
         1: Binary Inverted
         2: Threshold Truncated
         3: Threshold to Zero
         4: Threshold to Zero Inverted
       */
    
    @@threshold( src_gray, dst, threshold_value, max_BINARY_value,threshold_type );
    
      imshow("Threshold", dst );
    

    Here @---> Error


  • Qt Champions 2018

    @gauravsharma0190 What are src_gray, dst, threshold_value, max_BINARY_value,threshold_type? Where are they defined and initialized? Please note: these are NOT same as in MainWindow::on_onTrackball_clicked()!

    void Threshold_Demo( int, void* )
    {
      /* 0: Binary
         1: Binary Inverted
         2: Threshold Truncated
         3: Threshold to Zero
         4: Threshold to Zero Inverted
       */
    
    @@threshold( src_gray, dst, threshold_value, max_BINARY_value,threshold_type );
    
      imshow("Threshold", dst );
    
    


  • @jsulm
    Hey Good morning
    These are defined in the same function .cpp files.
    Yes These are not in mainwindow


  • Qt Champions 2018

    @gauravsharma0190 Did you initialize these variables? Do they have correct values when you call threshold()?



  • @jsulm
    Yes i initialize these with correct values.


  • Qt Champions 2018

    @gauravsharma0190 Are you sure? Did you verify using debugger? If they have correct values then I don't know why it's crashing...



  • @gauravsharma0190 said:

    void MainWindow::on_onTrackball_clicked()
    {
    int threshold_value = 0;
    int threshold_type = 3;
    int const max_value = 255;
    int const max_type = 4;
    // int const max_BINARY_value = 255;

    Mat src, src_gray, dst;
    

    // char* window_name = "Threshold Demo";

    //char* trackbar_type = "Type: \n 0: Binary \n 1: Binary Inverted \n 2: Truncate \n 3: To Zero \n 4: To Zero Inverted";
    //char* trackbar_value = "Value";
    
    
    
    
    /// Load image
    src = imread( "/home/pi/Desktop/b4.jpg");
    
    
      /// Convert the image to Gray
      cvtColor( src, src_gray, CV_BGR2GRAY );
    
      /// Create a window to display results
      namedWindow( "Threshold", CV_WINDOW_AUTOSIZE );
    
      /// Create Trackbar to choose type of Threshold
      createTrackbar( "Type: \n 0: Binary \n 1: Binary Inverted \n 2: Truncate \n 3: To Zero \n 4: To Zero Inverted","Threshold", &threshold_type, max_type, Threshold_Demo );
    
      createTrackbar( "value","Threshold", &threshold_value, max_value, Threshold_Demo );
    
      /// Call the function to initialize
    

    @@@ Threshold_Demo( 0, 0)

    }

    When I Comment the line Threshold _demo everything went OK!!!
    Results are coming but when i uncomment it everything crashes.


  • Lifetime Qt Champion

    Hi
    I have a teory ;)

    namedWindow

    void namedWindow(const string& winname, int flags=WINDOW_AUTOSIZE )

    It wants a ref, so i assume that the crash is that
    // char* window_name = "Threshold Demo";

    will run out of scope

    where as
    namedWindow( "Threshold", CV_WINDOW_AUTOSIZE );
    There "Threshold" is managed by the compiler and wont run out.

    To test this, please move
    char* window_name = "Threshold Demo";

    OUTSIDE the function so it last longer than function call.


  • Qt Champions 2018

    @gauravsharma0190 Please take a closer look at this code:

    void MainWindow::on_onTrackball_clicked()
    {
    int threshold_value = 0;
    int threshold_type = 3;
    int const max_value = 255;
    int const max_type = 4;
    // int const max_BINARY_value = 255;
    // These variables are LOCAL!
    Mat src, src_gray, dst;
    

    You use local variables in void MainWindow::on_onTrackball_clicked(). All these variables exist only in that function: Mat src, src_gray, dst;
    In Threshold_Demo() these variable are not visible (I have no idea why your code compiles? You probably defined these variables somewhere else again). I already pointed out this issue in one of my previous posts.

    void Threshold_Demo( int, void* )
    {
      /* 0: Binary
         1: Binary Inverted
         2: Threshold Truncated
         3: Threshold to Zero
         4: Threshold to Zero Inverted
       */
    // src_gray, dst, threshold_value, max_BINARY_value,threshold_type are GLOBAL! Where are they defined?
    @@threshold( src_gray, dst, threshold_value, max_BINARY_value,threshold_type );
    

    Please make really sure src_gray, dst, threshold_value, max_BINARY_value,threshold_type have valid values when you call threshold( )! Use debugger for this.



  • @jsulm
    Hey the ontrack.cpp file has these variable defined i havn't sent you full code
    here it is

    #include"onTrack.h"
    #include<imgproc.hpp>
     using namespace cv;
    using namespace std;
    int threshold_value=0;
    int threshold_type=3;
    int const max_BINARY_value=255;
    Mat src_gray,dst;
    
    void Threshold_Demo( int, void* )
    {
      /* 0: Binary
         1: Binary Inverted
         2: Threshold Truncated
         3: Threshold to Zero
         4: Threshold to Zero Inverted
       */
    
      threshold( src_gray, dst, threshold_value, max_BINARY_value,threshold_type );
    
      imshow( window_name, dst );
    }
    ......

  • Qt Champions 2018

    @gauravsharma0190 That is the problem I'm talking all the time! You do not initialize src_gray,dst from ontrack.cpp, so you use not properly initialized variables in Threshold_Demo(). As I said in MainWindow::on_onTrackball_clicked() you use local variables rc_gray,dst, not the ones from ontrack.cpp!
    So, again where are these variables initialized?

    // Where are they initialized?
    Mat src_gray,dst;
    
    void Threshold_Demo( int, void* )
    {
      /* 0: Binary
         1: Binary Inverted
         2: Threshold Truncated
         3: Threshold to Zero
         4: Threshold to Zero Inverted
       */
    


  • @jsulm said:

    That is the problem I'm talking all the time! You do not initialize src_gray,dst from ontrack.cpp, so you use not properly initialized variables in Threshold_Demo(). As I said in MainWindow::on_onTrackball_clicked() you use local variables rc_gray,dst, not the ones from ontrack.cpp!
    So, again where are these variables initialized?

    // Where are they initialized?
    Mat src_gray,dst;

    void Threshold_Demo( int, void* )
    {
    /* 0: Binary
    1: Binary Inverted
    2: Threshold Truncated
    3: Threshold to Zero
    4: Threshold to Zero Inverted
    */

    I initalized it in Mainwindow::onTrackBall_clicked().
    I am sending you.
    mainWindow.cpp*******

    #include "mainwindow.h"
    #include "ui_mainwindow.h"
    #include<opencv2/opencv.hpp>
    #include <opencv2/highgui/highgui.hpp>
    #include <opencv2/core/core.hpp>
    #include <opencv2/imgproc/imgproc.hpp>
    #include<QFileDialog>
    #include<QMessageBox>
    #include <iostream>
    #include<QProcess>
    #include "onTrackBall.h"
    #include<syscall.h>
    #include<signal.h>
    #include <string>
    #include<stdlib.h>
    #include<sys/ioctl.h>
    #include <fstream>
    #include<time.h>
    #include<QTimer>
    #include<QDateTime>
    //#include"onTrackBall.h"
    //#include"onTrackBall.c"
    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);
    
    }
    void MainWindow::on_onTrackball_clicked()
    {
        int threshold_value = 0;
        int threshold_type = 3;
        int const max_value = 255;
        int const max_type = 4;
       // int const max_BINARY_value = 255;
    
        Mat src, src_gray;
    
    
    
    
    
        /// Load image
        src = imread( "/home/pi/Desktop/b4.jpg");
    
    
          /// Convert the image to Gray
          cvtColor( src, src_gray, CV_BGR2GRAY );
    
          /// Create a window to display results
          namedWindow( "Threshold", CV_WINDOW_NORMAL );
    
          /// Create Trackbar to choose type of Threshold
          createTrackbar( "Type: \n 0: Binary \n 1: Binary Inverted \n 2: Truncate \n 3: To Zero \n 4: To Zero Inverted","Threshold", &threshold_type, max_type, Threshold_Demo );
    
          createTrackbar( "value","Threshold", &threshold_value, max_value, Threshold_Demo );
    
          /// Call the function to initialize
        Threshold_Demo( 0, 0 );
    
    
        /// Separate the image in 3 places ( B, G and R )
        vector<Mat> bgr_planes;
        split( src, bgr_planes );
    
        /// Establish the number of bins
        int histSize = 256;
    
        /// Set the ranges ( for B,G,R) )
        float range[] = { 0, 256 } ;
        const float* histRange = { range };
    
        bool uniform = true;
        bool accumulate = false;
    
        Mat b_hist, g_hist, r_hist;
    
        /// Compute the histograms:
        calcHist( &bgr_planes[0], 1, 0, Mat(), b_hist, 1, &histSize, &histRange, uniform, accumulate );
        calcHist( &bgr_planes[1], 1, 0, Mat(), g_hist, 1, &histSize, &histRange, uniform, accumulate );
        calcHist( &bgr_planes[2], 1, 0, Mat(), r_hist, 1, &histSize, &histRange, uniform, accumulate );
    
        // Draw the histograms for B, G and R
        int hist_w = 512; int hist_h = 400;
       int bin_w = cvRound( (double) hist_w/histSize );
    
        Mat histImage( hist_h, hist_w, CV_8UC3, Scalar( 0,0,0) );
    
        /// Normalize the result to [ 0, histImage.rows ]
        normalize(b_hist, b_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );
        normalize(g_hist, g_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );
        normalize(r_hist, r_hist, 0, histImage.rows, NORM_MINMAX, -1, Mat() );
    
        /// Draw for each channel
        for( int i = 1; i < histSize; i++ )
        {
            line( histImage, Point( bin_w*(i-1), hist_h - cvRound(b_hist.at<float>(i-1)) ) ,
                             Point( bin_w*(i), hist_h - cvRound(b_hist.at<float>(i)) ),
                             Scalar( 255, 0, 0), 2, 8, 0  );
            line( histImage, Point( bin_w*(i-1), hist_h - cvRound(g_hist.at<float>(i-1)) ) ,
                             Point( bin_w*(i), hist_h - cvRound(g_hist.at<float>(i)) ),
                             Scalar( 0, 255, 0), 2, 8, 0  );
            line( histImage, Point( bin_w*(i-1), hist_h - cvRound(r_hist.at<float>(i-1)) ) ,
                             Point( bin_w*(i), hist_h - cvRound(r_hist.at<float>(i)) ),
                             Scalar( 0, 0, 255), 2, 8, 0  );
        }
    
        /// Display
        namedWindow("calcHist Demo", CV_WINDOW_NORMAL );
        imshow("calcHist Demo", histImage );
      imwrite("calcHist Demo2.jpg", histImage);
    waitKey(-1);
    
    
      }
    ...

  • Qt Champions 2018

    @gauravsharma0190 Please read what I'm writing more carefully!
    In Mainwindow::onTrackBall_clicked() you don't initialize them! Because you use local variables there with same names:

    void MainWindow::on_onTrackball_clicked()
    {
         // Here src and src_gray are not the same as in ontrack.cpp!
         // Values you're assigning here to src and src_gray are only visible here but not in ontrack.cpp!
        Mat src, src_gray;
    

    I'm running out of ideas how to explain it. You should learn C++, especially the visibility and scope of variables.



  • @jsulm
    You mean to say in OnTrack_clicked()
    src and src_gray variable
    and in ontrack.cpp
    src_gray variable should be different.
    I can't get you.
    In Mainwindow::onTrackBall_clicked() you don't initialize them! Because you use local variables there with same names:

    void MainWindow::on_onTrackball_clicked()
    {
    // Here src and src_gray are not the same as in ontrack.cpp!
    // Values you're assigning here to src and src_gray are only visible here but not in ontrack.cpp!
    Here what is local variable in it.
    Local mean variable inside the function??
    And globle mean en tire the programme.


  • Qt Champions 2018

    @gauravsharma0190 No, I don't mean that they should be different. I mean the opposite: they need to be the same (but they are not).
    Local variable is a variable which is only visible in a certain scope, for example in a function. The variables in ontrack.cpp are only visible in ontrack.cpp, but not in MainWindow. In Mainwindow::onTrackBall_clicked() you declare OTHER variables with SAME names.
    What do you think which src_grey is used in Threshold_Demo( int, void* )? Is it the one from MainWindow::onTrackBall_clicked() or the one from ontrack.cpp?

    // src_gray here is not the same as in MainWindow::onTrackBall_clicked()
    Mat src_gray,dst;
    void Threshold_Demo( int, void* )
    {
      threshold( src_gray, dst, threshold_value, max_BINARY_value,threshold_type );
    }
    

    Actually you should pass the data to Threshold_Demo() as parameter:

    Mainwindow::onTrackBall_clicked()
    {
        Mat src, src_gray;
        ...
        Threshold_Demo(src_grey, /*what else needs to be passed from MainWindow to this function*/);
        ...
    }
    
    void Threshold_Demo(Mat &src_grey, ...)
    {
    


  • @jsulm
    OK it means src_gray value in .cpp file should be same as in mainwindow::on_Track clicked() src_gray value.
    Actually src_gray is image array.
    I did it by Define the value of src_grey in function as
    src=imread("/file.jpg);
    cvtColor( src, src_gray, CV_BGR2GRAY );
    so i will get src_gray value.


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