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alphachannel.cpp

/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
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** additional rights. These rights are described in the Nokia Qt LGPL
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** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
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#include <qapplication.h>
#include <qlabel.h>
#include <qpixmap.h>
#include <qprinter.h>
#include <qpainter.h>
#include <qfile.h>
#include <qdir.h>
#include <qfileinfo.h>

#if (QT_VERSION) >= 0x040000
#include <QtGui>
#include <QtCore>
#endif

00056 class MyClass : public QWidget
{
public:
     MyClass(QWidget *parent = 0) : QWidget(parent) { }

protected:
00062      void paintEvent(QPaintEvent *e)
     {
        /*QRadialGradient rg(50, 50, 50, 50, 50);
         rg.setColorAt(0, QColor::fromRgbF(1, 0, 0, 1));
         rg.setColorAt(1, QColor::fromRgbF(0, 0, 0, 0));
         QPainter pmp(&pm);
         pmp.fillRect(0, 0, 100, 100, rg);
         pmp.end();*/

      createImage();

      QPainter p(this);
      p.fillRect(rect(), Qt::white);

      p.drawPixmap(0, 0, pixmap);

      p.drawPixmap(100, 0, channelImage);
     }

00081     void createImage()
    {
//! [0]
      pixmap = QPixmap(100, 100);
      pixmap.fill(Qt::transparent);

      QRadialGradient gradient(50, 50, 50, 50, 50);
      gradient.setColorAt(0, QColor::fromRgbF(1, 0, 0, 1));
      gradient.setColorAt(1, QColor::fromRgbF(0, 0, 0, 0));
      QPainter painter(&pixmap);
      painter.fillRect(0, 0, 100, 100, gradient);

      channelImage = pixmap.alphaChannel();
      update();
//! [0]
    }

    QPixmap channelImage, pixmap; 
    QSize sizeHint() const { return QSize(500, 500); }
};

    

int main(int argc, char **argv)
{
     QApplication app(argc, argv);

     MyClass cl;
     cl.show();
     QObject::connect(&app, SIGNAL(lastWindowClosed()), &app, SLOT(quit()));

     int ret = app.exec();
     return ret;
}

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