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# imagecomposer.cpp Example File
painting/imagecomposition/imagecomposer.cpp

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        ** Copyright (C) 2006-2006 Trolltech ASA. All rights reserved.
        **
        ** This file is part of the example classes of the Qt Toolkit.
        **
        ** Licensees holding valid Qt Preview licenses may use this file in
        ** accordance with the Qt Preview License Agreement provided with the
        ** Software.
        **
        ** See http://www.trolltech.com/pricing.html or email sales@trolltech.com for
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        ** Contact info@trolltech.com if any conditions of this licensing are
        ** not clear to you.
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        ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
        ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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        ****************************************************************************/

        #include <QtGui>

        #include "imagecomposer.h"

        static const QSize resultSize(200, 200);

        ImageComposer::ImageComposer()
        {
            sourceButton = new QToolButton;
            sourceButton->setIconSize(resultSize);

            operatorComboBox = new QComboBox;
            addOp(QPainter::CompositionMode_SourceOver, tr("SourceOver"));
            addOp(QPainter::CompositionMode_DestinationOver, tr("DestinationOver"));
            addOp(QPainter::CompositionMode_Clear, tr("Clear"));
            addOp(QPainter::CompositionMode_Source, tr("Source"));
            addOp(QPainter::CompositionMode_Destination, tr("Destination"));
            addOp(QPainter::CompositionMode_SourceIn, tr("SourceIn"));
            addOp(QPainter::CompositionMode_DestinationIn, tr("DestinationIn"));
            addOp(QPainter::CompositionMode_SourceOut, tr("SourceOut"));
            addOp(QPainter::CompositionMode_DestinationOut, tr("DestinationOut"));
            addOp(QPainter::CompositionMode_SourceAtop, tr("SourceAtop"));
            addOp(QPainter::CompositionMode_DestinationAtop, tr("DestinationAtop"));
            addOp(QPainter::CompositionMode_Xor, tr("Xor"));

            destinationButton = new QToolButton;
            destinationButton->setIconSize(resultSize);

            equalLabel = new QLabel(tr("="));

            resultLabel = new QLabel;
            resultLabel->setMinimumWidth(resultSize.width());

            connect(sourceButton, SIGNAL(clicked()), this, SLOT(chooseSource()));
            connect(operatorComboBox, SIGNAL(activated(int)),
                    this, SLOT(recalculateResult()));
            connect(destinationButton, SIGNAL(clicked()),
                    this, SLOT(chooseDestination()));

            QGridLayout *mainLayout = new QGridLayout;
            mainLayout->addWidget(sourceButton, 0, 0, 3, 1);
            mainLayout->addWidget(operatorComboBox, 1, 1);
            mainLayout->addWidget(destinationButton, 0, 2, 3, 1);
            mainLayout->addWidget(equalLabel, 1, 3);
            mainLayout->addWidget(resultLabel, 0, 4, 3, 1);
            mainLayout->setSizeConstraint(QLayout::SetFixedSize);
            setLayout(mainLayout);

            resultImage = QImage(resultSize, QImage::Format_ARGB32_Premultiplied);

            loadImage(":/images/butterfly.png", &sourceImage, sourceButton);
            loadImage(":/images/checker.png", &destinationImage, destinationButton);

            setWindowTitle(tr("Image Composition"));
        }

        void ImageComposer::chooseSource()
        {
            chooseImage(tr("Choose Source Image"), &sourceImage, sourceButton);
        }

        void ImageComposer::chooseDestination()
        {
            chooseImage(tr("Choose Destination Image"), &destinationImage,
                        destinationButton);
        }

        void ImageComposer::recalculateResult()
        {
            QPainter::CompositionMode mode = currentMode();

            QPainter painter(&resultImage);
            painter.setCompositionMode(QPainter::CompositionMode_Source);
            painter.fillRect(resultImage.rect(), Qt::transparent);
            painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
            painter.drawImage(0, 0, destinationImage);
            painter.setCompositionMode(mode);
            painter.drawImage(0, 0, sourceImage);
            painter.setCompositionMode(QPainter::CompositionMode_DestinationOver);
            painter.fillRect(resultImage.rect(), Qt::white);
            painter.end();

            resultLabel->setPixmap(QPixmap::fromImage(resultImage));
        }

        void ImageComposer::addOp(QPainter::CompositionMode mode, const QString &name)
        {
            operatorComboBox->addItem(name, mode);
        }

        void ImageComposer::chooseImage(const QString &title, QImage *image,
                                        QToolButton *button)
        {
            QString fileName = QFileDialog::getOpenFileName(this, title);
            if (!fileName.isEmpty())
                loadImage(fileName, image, button);
        }

        void ImageComposer::loadImage(const QString &fileName, QImage *image,
                                      QToolButton *button)
        {
            image->load(fileName);

            QImage fixedImage(resultSize, QImage::Format_ARGB32_Premultiplied);
            QPainter painter(&fixedImage);
            painter.setCompositionMode(QPainter::CompositionMode_Source);
            painter.fillRect(fixedImage.rect(), Qt::transparent);
            painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
            painter.drawImage(imagePos(*image), *image);
            painter.end();
            button->setIcon(QPixmap::fromImage(fixedImage));

            *image = fixedImage;

            recalculateResult();
        }

        QPainter::CompositionMode ImageComposer::currentMode() const
        {
            return (QPainter::CompositionMode)
                   operatorComboBox->itemData(operatorComboBox->currentIndex()).toInt();
        }

        QPoint ImageComposer::imagePos(const QImage &image) const
        {
            return QPoint((resultSize.width() - image.width()) / 2,
                          (resultSize.height() - image.height()) / 2);
        }