(C++) How to draw a sprite on a sprite?

 

How to draw a sprite on a sprite? is a Qt FAQ when you want to stretchdraw differently scaled images on top of each other, like this image.

 

 

 

 

 

Project and source code

 

Operating system: Ubuntu 10.04 LTS Lucid Lynx

IDE: Qt Creator 2.0.0

Project type: Qt4 Console Application

Compiler: G++ 4.4.1

Libraries used:

• Boost: version 1.40
• Qt: version 4.7.0 (32 bit)

 

• View a screenshot of 'CppQtSpriteOnSprite' (png)
• Download the C++ Qt Creator project 'CppQtSpriteOnSprite' (zip)

 

 

 

 

 

CppQtSpriteOnSprite.pro

 

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#------------------------------------------------- # # Project created by QtCreator 2010-07-30T20:07:20 # #------------------------------------------------- QT += core gui TARGET = CppQtSpriteOnSprite TEMPLATE = app SOURCES += main.cpp\ dialog.cpp HEADERS += dialog.h FORMS += dialog.ui RESOURCES += \ resources.qrc

 

 

 

 

 

main.cpp

 

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#include <QtGui/QApplication> #include "dialog.h" int main(int argc, char *argv[]) {   QApplication a(argc, argv);   Dialog w;   w.show();   return a.exec(); }

 

 

 

 

 

dialog.h

 

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#ifndef DIALOG_H #define DIALOG_H #include <boost/shared_ptr.hpp> #include <QDialog> struct QTimer; namespace Ui {   class Dialog; } class Dialog : public QDialog {   Q_OBJECT public:   explicit Dialog(QWidget *parent = 0);   ~Dialog(); protected:   void changeEvent(QEvent *e); private:   Ui::Dialog *ui;   boost::shared_ptr<QTimer> m_timer;   void paintEvent(QPaintEvent * event); private slots:   void onTimer(); }; #endif // DIALOG_H

 

 

 

 

 

dialog.cpp

 

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#include <cassert> #include <QDesktopWidget> #include <QImage> #include <QPainter> #include <QPixmap> #include <QTimer> #include "dialog.h" #include "ui_dialog.h" Dialog::Dialog(QWidget *parent) :     QDialog(parent,Qt::Window), //To allow resizing     ui(new Ui::Dialog),     m_timer(new QTimer) {   ui->setupUi(this);   //Put the dialog in the screen center   const QRect screen = QApplication::desktop()->screenGeometry();   this->move( screen.center() - this->rect().center() );   //Make a timer tick ever 1000 ms   QObject::connect(m_timer.get(),SIGNAL(timeout()),this,SLOT(onTimer()));   m_timer->start(1000); } Dialog::~Dialog() {   delete ui; } void Dialog::changeEvent(QEvent *e) {   QDialog::changeEvent(e);   switch (e->type()) {   case QEvent::LanguageChange:     ui->retranslateUi(this);     break;   default:     break;   } } void Dialog::paintEvent(QPaintEvent *) {   //Start the painter   QPainter painter(this);   //Load the background from resources   QPixmap background(":/images/Background11x11.png");   assert(!background.isNull());   //StretchDraw the background on the widget   painter.drawPixmap(     ui->widget->rect(),     background);   //Load the sprite from resources   QPixmap sprite(":/images/Sprite22x22.png");   assert(!sprite.isNull());   //Choose a random x and y coordinate on a white pixel   int x = 0;   int y = 0;   while (1)   {     x = 1 + (std::rand() % 9);     y = 1 + (std::rand() % 9);     //The new position must be on a white pixel     if (background.toImage().pixel(x,y)       == QColor(255,255,255).rgb()) break;   }   //Determine the sprite's position on the painter   const int width = ui->widget->width();   const int height = ui->widget->height();   const double block_width = static_cast<double>(width) / 11.0;   const double block_height = static_cast<double>(height) / 11.0;   //Draw the sprite on the painter   painter.drawPixmap(     static_cast<double>(x) * block_width,     static_cast<double>(y) * block_height,     block_width,     block_height,     sprite); } void Dialog::onTimer() {   this->repaint(); }