Picture

This example shows how to make a picture, store it to a file, and read it as a set of drawing commands.

Implementation:

/****************************************************************************
** $Id: qt/picture.cpp   3.3.7   edited Aug 31 2005 $
**
** Copyright (C) 1992-2005 Trolltech AS.  All rights reserved.
**
** This file is part of an example program for Qt.  This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/

#include <qapplication.h>
#include <qpainter.h>
#include <qpicture.h>
#include <qpixmap.h>
#include <qwidget.h>
#include <qmessagebox.h>
#include <qfile.h>
#include <ctype.h>


void paintCar( QPainter *p )                    // paint a car
{
    QPointArray a;
    QBrush brush( Qt::yellow, Qt::SolidPattern );
    p->setBrush( brush );                       // use solid, yellow brush

    a.setPoints( 5, 50,50, 350,50, 450,120, 450,250, 50,250 );
    p->drawPolygon( a );                        // draw car body

    QFont f( "courier", 12, QFont::Bold );
    p->setFont( f );

    QColor windowColor( 120, 120, 255 );        // a light blue color
    brush.setColor( windowColor );              // set this brush color
    p->setBrush( brush );                       // set brush
    p->drawRect( 80, 80, 250, 70 );             // car window
    p->drawText( 180, 80, 150, 70, Qt::AlignCenter, "--  Qt  --\nTrolltech AS" );

    QPixmap pixmap;
    if ( pixmap.load("flag.bmp") )              // load and draw image
        p->drawPixmap( 100, 85, pixmap );

    p->setBackgroundMode( Qt::OpaqueMode );     // set opaque mode
    p->setBrush( Qt::DiagCrossPattern );        // black diagonal cross pattern
    p->drawEllipse( 90, 210, 80, 80 );          // back wheel
    p->setBrush( Qt::CrossPattern );            // black cross fill pattern
    p->drawEllipse( 310, 210, 80, 80 );         // front wheel
}


class PictureDisplay : public QWidget           // picture display widget
{
public:
    PictureDisplay( const char *fileName );
   ~PictureDisplay();
protected:
    void        paintEvent( QPaintEvent * );
    void        keyPressEvent( QKeyEvent * );
private:
    QPicture   *pict;
    QString     name;
};

PictureDisplay::PictureDisplay( const char *fileName )
{
    pict = new QPicture;
    name = fileName;
    if ( !pict->load(fileName) ) {              // cannot load picture
        delete pict;
        pict = 0;
        name.sprintf( "Not able to load picture: %s", fileName );
    }
}

PictureDisplay::~PictureDisplay()
{
    delete pict;
}

void PictureDisplay::paintEvent( QPaintEvent * )
{
    QPainter paint( this );                     // paint widget
    if ( pict )
        paint.drawPicture( *pict );             // draw picture
    else
        paint.drawText( rect(), AlignCenter, name );
}

void PictureDisplay::keyPressEvent( QKeyEvent *k )
{
    switch ( tolower(k->ascii()) ) {
        case 'r':                               // reload
            pict->load( name );
            update();
            break;
        case 'q':                               // quit
            QApplication::exit();
            break;
    }
}


int main( int argc, char **argv )
{
    QApplication a( argc, argv );               // QApplication required!

    const char *fileName = "car.pic";           // default picture file name

    if ( argc == 2 )                            // use argument as file name
        fileName = argv[1];

    if ( !QFile::exists(fileName) ) {
        QPicture pict;                          // our picture
        QPainter paint;                         // our painter

        paint.begin( &pict );                   // begin painting onto picture
        paintCar( &paint );                     // paint!
        paint.end();                            // painting done

        pict.save( fileName );                  // save picture
        QMessageBox::information(0, "Qt Example - Picture", "Saved.  Run me again!");
        return 0;
    } else {
        PictureDisplay test( fileName );        // create picture display
        a.setMainWidget( &test);                // set main widget
        test.setCaption("Qt Example - Picture");
        test.show();                            // show it

        return a.exec();                        // start event loop
    }
}

See also Examples.