Scaling QGraphicsPixmapItem

Article Metadata

---

Tested with

Devices(s): Nokia 5800 XpressMusic

---

Compatibility

Platform(s): S60 3rd Edition, FP1, FP2
S60 5th Edition

---

Platform Security

Signing Required: Self-Signed

Capabilities: None

---

Article

Keywords: QGraphicsPixmapItem

Created: tepaa (17 Apr 2009)

Last edited: hamishwillee (11 Oct 2012)

Overview

This code snippets shows how to scale QGraphicsPixmapItem into a defined size. QGraphicsPixmapItem is an item of the Qt Graphics Framework.

Header

#include <QGraphicsPixmapItem>
class MyPixmapItem: public QGraphicsPixmapItem
    {
    public:
        MyPixmapItem(const QPixmap &pixmap, QGraphicsItem *parentItem=0, int size=0);
        ~MyPixmapItem();
 
    public:
        QRectF boundingRect() const;
        void paint(QPainter *painter,
                   const QStyleOptionGraphicsItem *option, QWidget *widget=0);
        void setSize(int size);
 
    private:
        int m_size;
    };

Source

MyPixmapItem::MyPixmapItem(const QPixmap &pixmap, QGraphicsItem *parentItem, int size)
: QGraphicsPixmapItem(pixmap,parentItem)
    {
    setCacheMode(NoCache);
    setSize(size);
    }
 
MyPixmapItem::~MyPixmapItem()
    {
    }
 
void MyPixmapItem::setSize(int size)
    {
    this->m_size = size;
    }
 
QRectF MyPixmapItem::boundingRect() const
    {
    // Return defined 'size'
    return QRectF(QPointF(0,0),QSizeF(m_size,m_size));
    }
 
void MyPixmapItem::paint(QPainter *painter, const QStyleOptionGraphicsItem*, QWidget*)
    {
    // Scale QGraphicsPixmapItem to wanted 'size' and keep the aspect ratio using boundingRect()
    painter->drawPixmap(boundingRect().toRect(), pixmap());
 
    // NOTE: Does not use base class paint for painting now, that does not scale QPixmap
    //QGraphicsPixmapItem::paint(painter, option, widget);
    }

Using MyPixmapItem can be implemented as shown:

    QGraphicsScene* m_graphicsScene = new QGraphicsScene();
    QGraphicsView* m_graphicsView = new QGraphicsView(m_graphicsScene, this);
    m_graphicsScene->setSceneRect(this->rect());
 
    // Create MyPixmapItem from png from the same directory where exe file is
    QPixmap p(qApp->applicationDirPath() + QDir::separator() +"candle.png");
    MyPixmapItem* pixmapItem = new MyPixmapItem(p,0,p.width()*0.5);
    m_graphicsScene->addItem(pixmapItem)

Postconditions

QGraphicsPixmapItem has been scaled.

Related articles

Scaling QPixmap image