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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
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** GNU Lesser General Public License Usage
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** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
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**
** GNU General Public License Usage
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****************************************************************************/
/*!
\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
*/
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