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This example implements the famous scribble example. You can draw around in the canvas with different pens and save the result as picture.
Header file:
/**************************************************************************** ** $Id: qt/scribble.h 3.1.2 edited Nov 8 10:35 $ ** ** Copyright ( C ) 1992-2000 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. ** *****************************************************************************/ #ifndef SCRIBBLE_H #define SCRIBBLE_H #include <qmainwindow.h> #include <qpen.h> #include <qpoint.h> #include <qpixmap.h> #include <qwidget.h> #include <qstring.h> #include <qpointarray.h> class QMouseEvent; class QResizeEvent; class QPaintEvent; class QToolButton; class QSpinBox; class Canvas : public QWidget { Q_OBJECT public: Canvas( QWidget *parent = 0, const char *name = 0 ); void setPenColor( const QColor &c ) { pen.setColor( c ); } void setPenWidth( int w ) { pen.setWidth( w ); } QColor penColor() { return pen.color(); } int penWidth() { return pen.width(); } void save( const QString &filename, const QString &format ); void clearScreen(); protected: void mousePressEvent( QMouseEvent *e ); void mouseReleaseEvent( QMouseEvent *e ); void mouseMoveEvent( QMouseEvent *e ); void resizeEvent( QResizeEvent *e ); void paintEvent( QPaintEvent *e ); QPen pen; QPointArray polyline; bool mousePressed; QPixmap buffer; }; class Scribble : public QMainWindow { Q_OBJECT public: Scribble( QWidget *parent = 0, const char *name = 0 ); protected: Canvas* canvas; QSpinBox *bPWidth; QToolButton *bPColor, *bSave, *bClear; protected slots: void slotSave(); void slotColor(); void slotWidth( int ); void slotClear(); }; #endif
Implementation:
/**************************************************************************** ** $Id: qt/scribble.cpp 3.1.2 edited Nov 8 10:35 $ ** ** Copyright ( C ) 1992-2000 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 "scribble.h" #include <qapplication.h> #include <qevent.h> #include <qpainter.h> #include <qtoolbar.h> #include <qtoolbutton.h> #include <qspinbox.h> #include <qtooltip.h> #include <qrect.h> #include <qpoint.h> #include <qcolordialog.h> #include <qfiledialog.h> #include <qcursor.h> #include <qimage.h> #include <qstrlist.h> #include <qpopupmenu.h> #include <qintdict.h> const bool no_writing = FALSE; Canvas::Canvas( QWidget *parent, const char *name ) : QWidget( parent, name, WStaticContents ), pen( Qt::red, 3 ), polyline(3), mousePressed( FALSE ), buffer( width(), height() ) { if ((qApp->argc() > 0) && !buffer.load(qApp->argv()[1])) buffer.fill( colorGroup().base() ); setBackgroundMode( QWidget::PaletteBase ); #ifndef QT_NO_CURSOR setCursor( Qt::crossCursor ); #endif } void Canvas::save( const QString &filename, const QString &format ) { if ( !no_writing ) buffer.save( filename, format.upper() ); } void Canvas::clearScreen() { buffer.fill( colorGroup().base() ); repaint( FALSE ); } void Canvas::mousePressEvent( QMouseEvent *e ) { mousePressed = TRUE; polyline[2] = polyline[1] = polyline[0] = e->pos(); } void Canvas::mouseReleaseEvent( QMouseEvent * ) { mousePressed = FALSE; } void Canvas::mouseMoveEvent( QMouseEvent *e ) { if ( mousePressed ) { QPainter painter; painter.begin( &buffer ); painter.setPen( pen ); polyline[2] = polyline[1]; polyline[1] = polyline[0]; polyline[0] = e->pos(); painter.drawPolyline( polyline ); painter.end(); QRect r = polyline.boundingRect(); r = r.normalize(); r.setLeft( r.left() - penWidth() ); r.setTop( r.top() - penWidth() ); r.setRight( r.right() + penWidth() ); r.setBottom( r.bottom() + penWidth() ); bitBlt( this, r.x(), r.y(), &buffer, r.x(), r.y(), r.width(), r.height() ); } } void Canvas::resizeEvent( QResizeEvent *e ) { QWidget::resizeEvent( e ); int w = width() > buffer.width() ? width() : buffer.width(); int h = height() > buffer.height() ? height() : buffer.height(); QPixmap tmp( buffer ); buffer.resize( w, h ); buffer.fill( colorGroup().base() ); bitBlt( &buffer, 0, 0, &tmp, 0, 0, tmp.width(), tmp.height() ); } void Canvas::paintEvent( QPaintEvent *e ) { QWidget::paintEvent( e ); QMemArray<QRect> rects = e->region().rects(); for ( uint i = 0; i < rects.count(); i++ ) { QRect r = rects[(int)i]; bitBlt( this, r.x(), r.y(), &buffer, r.x(), r.y(), r.width(), r.height() ); } } //------------------------------------------------------ Scribble::Scribble( QWidget *parent, const char *name ) : QMainWindow( parent, name ) { canvas = new Canvas( this ); setCentralWidget( canvas ); QToolBar *tools = new QToolBar( this ); bSave = new QToolButton( QPixmap(), "Save", "Save as PNG image", this, SLOT( slotSave() ), tools ); bSave->setText( "Save as..." ); tools->addSeparator(); bPColor = new QToolButton( QPixmap(), "Choose Pen Color", "Choose Pen Color", this, SLOT( slotColor() ), tools ); bPColor->setText( "Choose Pen Color..." ); tools->addSeparator(); bPWidth = new QSpinBox( 1, 20, 1, tools ); QToolTip::add( bPWidth, "Choose Pen Width" ); connect( bPWidth, SIGNAL( valueChanged( int ) ), this, SLOT( slotWidth( int ) ) ); bPWidth->setValue( 3 ); tools->addSeparator(); bClear = new QToolButton( QPixmap(), "Clear Screen", "Clear Screen", this, SLOT( slotClear() ), tools ); bClear->setText( "Clear Screen" ); } void Scribble::slotSave() { QPopupMenu *menu = new QPopupMenu( 0 ); QIntDict<QString> formats; formats.setAutoDelete( TRUE ); for ( unsigned int i = 0; i < QImageIO::outputFormats().count(); i++ ) { QString str = QString( QImageIO::outputFormats().at( i ) ); formats.insert( menu->insertItem( QString( "%1..." ).arg( str ) ), new QString( str ) ); } menu->setMouseTracking( TRUE ); int id = menu->exec( bSave->mapToGlobal( QPoint( 0, bSave->height() + 1 ) ) ); if ( id != -1 ) { QString format = *formats[ id ]; QString filename = QFileDialog::getSaveFileName( QString::null, QString( "*.%1" ).arg( format.lower() ), this ); if ( !filename.isEmpty() ) canvas->save( filename, format ); } delete menu; } void Scribble::slotColor() { QColor c = QColorDialog::getColor( canvas->penColor(), this ); if ( c.isValid() ) canvas->setPenColor( c ); } void Scribble::slotWidth( int w ) { canvas->setPenWidth( w ); } void Scribble::slotClear() { canvas->clearScreen(); }
Main:
/**************************************************************************** ** $Id: qt/main.cpp 3.1.2 edited Nov 8 10:35 $ ** ** Copyright ( C ) 1992-2000 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 "scribble.h" #include <qapplication.h> int main( int argc, char **argv ) { QApplication a( argc, argv ); Scribble scribble; scribble.resize( 500, 350 ); scribble.setCaption("Qt Example - Scribble"); a.setMainWidget( &scribble ); if ( QApplication::desktop()->width() > 550 && QApplication::desktop()->height() > 366 ) scribble.show(); else scribble.showMaximized(); return a.exec(); }
See also Examples.
Copyright © 2003 Trolltech | Trademarks | Qt version 3.1.2
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