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+/****************************************************************************
+**
+** 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.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** 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
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
+** package.
+**
+** 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
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at qt-sales@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+ \example painting/imagecomposition
+ \title Image Composition Example
+
+ The Image Composition example lets the user combine images
+ together using any composition mode supported by QPainter, described
+ in detail in \l{QPainter#Composition Modes}{Composition Modes}.
+
+ \image imagecomposition-example.png
+
+ \section1 Setting Up The Resource File
+
+ The Image Composition example requires two source images,
+ \e butterfly.png and \e checker.png that are embedded within
+ \e imagecomposition.qrc. The file contains the following code:
+
+ \quotefile examples/painting/imagecomposition/imagecomposition.qrc
+
+ For more information on resource files, see \l{The Qt Resource System}.
+
+ \section1 ImageComposer Class Definition
+
+ The \c ImageComposer class is a subclass of QWidget that implements three
+ private slots, \c chooseSource(), \c chooseDestination(), and
+ \c recalculateResult().
+
+ \snippet examples/painting/imagecomposition/imagecomposer.h 0
+
+ In addition, \c ImageComposer consists of five private functions,
+ \c addOp(), \c chooseImage(), \c loadImage(), \c currentMode(), and
+ \c imagePos(), as well as private instances of QToolButton, QComboBox,
+ QLabel, and QImage.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.h 1
+
+ \section1 ImageComposer Class Implementation
+
+ We declare a QSize object, \c resultSize, as a static constant with width
+ and height equal to 200.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 0
+
+ Within the constructor, we instantiate a QToolButton object,
+ \c sourceButton and set its \l{QAbstractButton::setIconSize()}{iconSize}
+ property to \c resultSize. The \c operatorComboBox is instantiated and
+ then populated using the \c addOp() function. This function accepts a
+ QPainter::CompositionMode, \a mode, and a QString, \a name, representing
+ the name of the composition mode.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 1
+
+ The \c destinationButton is instantiated and its
+ \l{QAbstractButton::setIconSize()}{iconSize} property is set to
+ \c resultSize as well. The \l{QLabel}s \c equalLabel and \c resultLabel
+ are created and \c{resultLabel}'s \l{QWidget::setMinimumWidth()}
+ {minimumWidth} is set.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 2
+
+ We connect the following signals to their corresponding slots:
+ \list
+ \o \c{sourceButton}'s \l{QPushButton::clicked()}{clicked()} signal is
+ connected to \c chooseSource(),
+ \o \c{operatorComboBox}'s \l{QComboBox::activated()}{activated()}
+ signal is connected to \c recalculateResult(), and
+ \o \c{destinationButton}'s \l{QToolButton::clicked()}{clicked()} signal
+ is connected to \c chooseDestination().
+ \endlist
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 3
+
+ A QGridLayout, \c mainLayout, is used to place all the widgets. Note
+ that \c{mainLayout}'s \l{QLayout::setSizeConstraint()}{sizeConstraint}
+ property is set to QLayout::SetFixedSize, which means that
+ \c{ImageComposer}'s size cannot be resized at all.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 4
+
+ We create a QImage, \c resultImage, and we invoke \c loadImage() twice
+ to load both the image files in our \e imagecomposition.qrc file. Then,
+ we set the \l{QWidget::setWindowTitle()}{windowTitle} property to
+ "Image Composition".
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 5
+
+ The \c chooseSource() and \c chooseDestination() functions are
+ convenience functions that invoke \c chooseImage() with specific
+ parameters.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 6
+ \codeline
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 7
+
+ The \c chooseImage() function loads an image of the user's choice,
+ depending on the \a title, \a image, and \a button.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 10
+
+ The \c recalculateResult() function is used to calculate amd display the
+ result of combining the two images together with the user's choice of
+ composition mode.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 8
+
+ The \c addOp() function adds an item to the \c operatorComboBox using
+ \l{QComboBox}'s \l{QComboBox::addItem()}{addItem} function. This function
+ accepts a QPainter::CompositionMode, \a mode, and a QString, \a name. The
+ rectangle is filled with Qt::Transparent and both the \c sourceImage and
+ \c destinationImage are painted, before displaying it on \c resultLabel.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 9
+
+ The \c loadImage() function paints a transparent background using
+ \l{QPainter::fillRect()}{fillRect()} and draws \c image in a
+ centralized position using \l{QPainter::drawImage()}{drawImage()}.
+ This \c image is then set as the \c{button}'s icon.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 11
+
+ The \c currentMode() function returns the composition mode currently
+ selected in \c operatorComboBox.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 12
+
+ We use the \c imagePos() function to ensure that images loaded onto the
+ QToolButton objects, \c sourceButton and \c destinationButton, are
+ centralized.
+
+ \snippet examples/painting/imagecomposition/imagecomposer.cpp 13
+
+ \section1 The \c main() Function
+
+ The \c main() function instantiates QApplication and \c ImageComposer
+ and invokes its \l{QWidget::show()}{show()} function.
+
+ \snippet examples/painting/imagecomposition/main.cpp 0
+
+ */