This Qt example shows how to create a GUI around a program that displays a rotating image, like this screenshot (png).

Download the Qt Project of 'QtExample19' (zip)

Operating system: Ubuntu 10.04 LTS Lucid Lynx

Project type: Qt4 GUI Application

Qt: version 4.7.0 (32 bit)

Qt project file


#-------------------------------------------------

#

# Project created by QtCreator 2010-08-06T12:45:13

#

#-------------------------------------------------

QT       += core gui

TARGET = CppQtExample19

TEMPLATE = app

SOURCES += main.cpp\

        dialogmain.cpp

HEADERS  += dialogmain.h

FORMS    += dialogmain.ui

RESOURCES += \

    resources.qrc

Source code

main.cpp


#include <QtGui/QApplication>

#include "dialogmain.h"



int main(int argc, char *argv[])

{

  QApplication a(argc, argv);

  DialogMain w;

  w.show();

  return a.exec();

}

dialogmain.h


#ifndef DIALOGMAIN_H

#define DIALOGMAIN_H



#include <QDialog>



struct QGraphicsScene;

struct QGraphicsPixmapItem;



namespace Ui {

  class DialogMain;

}



class DialogMain : public QDialog

{

  Q_OBJECT



public:

  explicit DialogMain(QWidget *parent = 0);

  ~DialogMain();



protected:

  void changeEvent(QEvent *e);



private:

  Ui::DialogMain *ui;

  QTimer * const m_timer;

  QGraphicsScene * const m_scene;

  QGraphicsPixmapItem * const m_sprite;

  double m_angle;



  void resizeEvent(QResizeEvent*);

  void keyPressEvent(QKeyEvent* e);



private slots:

  void onTick();

  void onCheck();

  void onButtonLeft();

  void onButtonRight();

};



#endif // DIALOGMAIN_H

dialogmain.cpp


#include <cassert>

#include <cmath>

#include <iostream>



#include <QDesktopWidget>

#include <QGraphicsPixmapItem>

#include <QGraphicsScene>

#include <QKeyEvent>

#include <QTimer>



#include "dialogmain.h"

#include "ui_dialogmain.h"



DialogMain::DialogMain(QWidget *parent) :

  QDialog(parent),

  ui(new Ui::DialogMain),

  m_timer(new QTimer(this)),

  m_scene(new QGraphicsScene(this)),

  m_sprite(new QGraphicsPixmapItem),

  m_angle(0.0)

{

  ui->setupUi(this);



  //Load the sprite

  m_sprite->setPixmap(QPixmap(":/images/R.png"));

  assert(!m_sprite->pixmap().isNull());



  //Set the center of the sprite for rotation

  m_sprite->setTransformOriginPoint(

    static_cast<double>(m_sprite->pixmap().width()) / 2.0,

    static_cast<double>(m_sprite->pixmap().height()) / 2.0);



  //Add the sprite to the scene

  m_scene->addItem(m_sprite);



  //Add the scene to the view

  ui->graphicsView->setScene(m_scene);



  //Connect and start a timer

  QObject::connect(m_timer,SIGNAL(timeout()),this,SLOT(onTick()));

  QObject::connect(ui->check_auto_rotate,SIGNAL(clicked()),this,SLOT(onCheck()));

  QObject::connect(ui->button_left,SIGNAL(clicked()),this,SLOT(onButtonLeft()));

  QObject::connect(ui->button_right,SIGNAL(clicked()),this,SLOT(onButtonRight()));





  //Start the timer

  m_timer->start(100);



  this->setGeometry(0,0,

    static_cast<int>(640),

    static_cast<int>(640));

  const QRect screen = QApplication::desktop()->screenGeometry();

  this->move( screen.center() - this->rect().center() );

}



DialogMain::~DialogMain()

{

  delete ui;

  delete m_sprite;

}



void DialogMain::changeEvent(QEvent *e)

{

  QDialog::changeEvent(e);

  switch (e->type()) {

  case QEvent::LanguageChange:

    ui->retranslateUi(this);

    break;

  default:

    break;

  }

}



//Sets the scale of the maze

void DialogMain::resizeEvent(QResizeEvent*)

{

  const int size = std::max(

    m_sprite->pixmap().width(),

    m_sprite->pixmap().height());



  const double scale = 0.9

    * std::min(ui->graphicsView->width(),

        ui->graphicsView->height())

    / (static_cast<double>(size) * std::sqrt(2.0));

  m_sprite->setScale(scale);

}



void DialogMain::keyPressEvent(QKeyEvent* e)

{

  switch (e->key())

  {

    case Qt::Key_Left: case Qt::Key_Minus: case Qt::Key_A:

      m_angle-=1.0;

      m_sprite->setRotation(m_angle);

      break;

    case Qt::Key_Right: case Qt::Key_Plus: case Qt::Key_D:

      m_angle+=1.0;

      m_sprite->setRotation(m_angle);

      break;

  }

}



void DialogMain::onTick()

{

  m_angle+=1.0;

  m_sprite->setRotation(m_angle);

}



void DialogMain::onCheck()

{

  if (ui->check_auto_rotate->isChecked())

    m_timer->start();

  else

    m_timer->stop();

}



void DialogMain::onButtonLeft()

{

  m_angle-=1.0;

  m_sprite->setRotation(m_angle);

}



void DialogMain::onButtonRight()

{

  m_angle+=1.0;

  m_sprite->setRotation(m_angle);

}

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(C++) Qt example 19: GUI around image rotation

Qt project file

Source code

main.cpp

dialogmain.h

dialogmain.cpp