Declaration of function and use it

[jsulm]

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

[gauravsharma0190]

@jsulm
Yes i initialize these with correct values.

[jsulm]

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

[gauravsharma0190]

@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.

[mrjj]

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.

[jsulm]

@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.

[gauravsharma0190]

@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 );
}
......

[jsulm]

@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
   */

[gauravsharma0190]

@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);


  }
...

[jsulm]

@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.

[gauravsharma0190]

@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.

[jsulm]

@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, ...)
{

[gauravsharma0190]

@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.