Hi everyone. I have a problem, I'm creating a simple Image Processing app, at part of brightness adjustment i can't run this function, when it's called then app will be crashed. I have two forms, one of form is mainwindow, one else is sub form to adjust brightness.

Qt Code: 
  1. //mainwindow.cpp
  2.  
  3. void MainWindow::brightnessProcessing(int value)
  4. {
  5.     QImage image = imageLabel->pixmap()->toImage();
  6.     int w = image.width();
  7.     int h = image.height();
  8.     QColor c;
  9.     int r, g, b;
  10.     for(int i=0; i<h; i++)
  11.         for(int j=0; j<w; j++) {
  12.             c = image.pixel(i, j);
  13.             r = c.red()+value;
  14.             g = c.green()+value;
  15.             b = c.blue()+value;
  16.             image.setPixel(i, j, qRgb(r, g, b));
  17.         }
  18.     imageLabel->setPixmap(QPixmap::fromImage(image));
  19. }
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Qt Code: 
  1. //mainwindow.h
  2.  
  3. #ifndef MAINWINDOW_H
  4. #define MAINWINDOW_H
  5.  
  6. #include <QMainWindow>
  7. #include <QtWidgets>
  8.  
  9. namespace Ui {
  10. class MainWindow;
  11. }
  12.  
  13. class MainWindow : public QMainWindow
  14. {
  15.     Q_OBJECT
  16.  
  17. public:
  18.     explicit MainWindow(QWidget *parent = 0);
  19.     ~MainWindow();
  20.     void brightnessProcessing(int value);
  21.  
  22. private slots:
  23.     ..........
  24.  
  25. private:
  26.     Ui::MainWindow *ui;
  27.     QImage *image;
  28.     QLabel *imageLabel;
  29.     QScrollArea *scrollArea;
  30.     QScrollBar *scrollBar;
  31.     double scaleFactor;
  32.  
  33.     void scaleImage(double factor);
  34.     void adjustScrollBar(QScrollBar *scrollBar, double factor);
  35. };
  36.  
  37. #endif // MAINWINDOW_H
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Qt Code: 
  1. //brightnesscontrast.cpp
  2.  
  3. void BrightnessContrast::on_horizontalSliderBrightness_valueChanged(int value)
  4. {
  5.     ui->lineEditBrightness->setText(QString::number(value));
  6.     respond.brightnessProcessing(value);
  7. }
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Qt Code: 
  1. //brightnesscontrast.h
  2.  
  3. #ifndef BRIGHTNESSCONTRAST_H
  4. #define BRIGHTNESSCONTRAST_H
  5.  
  6. #include <QDialog>
  7. #include <QtWidgets>
  8. #include "mainwindow.h"
  9.  
  10. namespace Ui {
  11. class BrightnessContrast;
  12. }
  13.  
  14. class BrightnessContrast : public QDialog
  15. {
  16.     Q_OBJECT
  17.  
  18. public:
  19.     explicit BrightnessContrast(QWidget *parent = 0);
  20.     ~BrightnessContrast();
  21.  
  22. private slots:
  23.     void on_horizontalSliderBrightness_valueChanged(int value);
  24.  
  25.     void on_horizontalSliderContrast_valueChanged(int value);
  26.  
  27. private:
  28.     Ui::BrightnessContrast *ui;
  29.     MainWindow respond;
  30. };
  31.  
  32. #endif // BRIGHTNESSCONTRAST_H
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anyhelp!