166 lines
6.4 KiB
Plaintext
166 lines
6.4 KiB
Plaintext
/****************************************************************************
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**
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** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
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** Contact: http://www.qt-project.org/
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**
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** This file is part of the documentation of the Qt Toolkit.
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**
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** $QT_BEGIN_LICENSE:FDL$
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** GNU Free Documentation License
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** Alternatively, this file may be used under the terms of the GNU Free
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** Documentation License version 1.3 as published by the Free Software
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** Foundation and appearing in the file included in the packaging of
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** this file.
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**
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** Other Usage
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** Alternatively, this file may be used in accordance with the terms
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** and conditions contained in a signed written agreement between you
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** and Nokia.
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**
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**
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**
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**
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**
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** $QT_END_LICENSE$
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**
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****************************************************************************/
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/*!
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\example widgets/painting/imagecomposition
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\title Image Composition Example
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The Image Composition example lets the user combine images
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together using any composition mode supported by QPainter, described
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in detail in \l{QPainter#Composition Modes}{Composition Modes}.
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\image imagecomposition-example.png
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\section1 Setting Up The Resource File
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The Image Composition example requires two source images,
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\e butterfly.png and \e checker.png that are embedded within
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\e imagecomposition.qrc. The file contains the following code:
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\quotefile widgets/painting/imagecomposition/imagecomposition.qrc
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For more information on resource files, see \l{The Qt Resource System}.
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\section1 ImageComposer Class Definition
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The \c ImageComposer class is a subclass of QWidget that implements three
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private slots, \c chooseSource(), \c chooseDestination(), and
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\c recalculateResult().
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\snippet widgets/painting/imagecomposition/imagecomposer.h 0
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In addition, \c ImageComposer consists of five private functions,
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\c addOp(), \c chooseImage(), \c loadImage(), \c currentMode(), and
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\c imagePos(), as well as private instances of QToolButton, QComboBox,
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QLabel, and QImage.
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\snippet widgets/painting/imagecomposition/imagecomposer.h 1
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\section1 ImageComposer Class Implementation
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We declare a QSize object, \c resultSize, as a static constant with width
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and height equal to 200.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 0
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Within the constructor, we instantiate a QToolButton object,
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\c sourceButton and set its \l{QAbstractButton::setIconSize()}{iconSize}
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property to \c resultSize. The \c operatorComboBox is instantiated and
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then populated using the \c addOp() function. This function accepts a
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QPainter::CompositionMode, \a mode, and a QString, \a name, representing
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the name of the composition mode.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 1
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The \c destinationButton is instantiated and its
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\l{QAbstractButton::setIconSize()}{iconSize} property is set to
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\c resultSize as well. The \l{QLabel}s \c equalLabel and \c resultLabel
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are created and \c{resultLabel}'s \l{QWidget::setMinimumWidth()}
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{minimumWidth} is set.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 2
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We connect the following signals to their corresponding slots:
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\list
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\li \c{sourceButton}'s \l{QPushButton::clicked()}{clicked()} signal is
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connected to \c chooseSource(),
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\li \c{operatorComboBox}'s \l{QComboBox::activated()}{activated()}
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signal is connected to \c recalculateResult(), and
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\li \c{destinationButton}'s \l{QToolButton::clicked()}{clicked()} signal
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is connected to \c chooseDestination().
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\endlist
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 3
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A QGridLayout, \c mainLayout, is used to place all the widgets. Note
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that \c{mainLayout}'s \l{QLayout::setSizeConstraint()}{sizeConstraint}
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property is set to QLayout::SetFixedSize, which means that
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\c{ImageComposer}'s size cannot be resized at all.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 4
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We create a QImage, \c resultImage, and we invoke \c loadImage() twice
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to load both the image files in our \e imagecomposition.qrc file. Then,
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we set the \l{QWidget::setWindowTitle()}{windowTitle} property to
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"Image Composition".
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 5
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The \c chooseSource() and \c chooseDestination() functions are
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convenience functions that invoke \c chooseImage() with specific
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parameters.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 6
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\codeline
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 7
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The \c chooseImage() function loads an image of the user's choice,
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depending on the \a title, \a image, and \a button.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 10
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The \c recalculateResult() function is used to calculate amd display the
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result of combining the two images together with the user's choice of
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composition mode.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 8
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The \c addOp() function adds an item to the \c operatorComboBox using
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\l{QComboBox}'s \l{QComboBox::addItem()}{addItem} function. This function
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accepts a QPainter::CompositionMode, \a mode, and a QString, \a name. The
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rectangle is filled with Qt::Transparent and both the \c sourceImage and
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\c destinationImage are painted, before displaying it on \c resultLabel.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 9
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The \c loadImage() function paints a transparent background using
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\l{QPainter::fillRect()}{fillRect()} and draws \c image in a
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centralized position using \l{QPainter::drawImage()}{drawImage()}.
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This \c image is then set as the \c{button}'s icon.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 11
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The \c currentMode() function returns the composition mode currently
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selected in \c operatorComboBox.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 12
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We use the \c imagePos() function to ensure that images loaded onto the
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QToolButton objects, \c sourceButton and \c destinationButton, are
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centralized.
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\snippet widgets/painting/imagecomposition/imagecomposer.cpp 13
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\section1 The \c main() Function
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The \c main() function instantiates QApplication and \c ImageComposer
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and invokes its \l{QWidget::show()}{show()} function.
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\snippet widgets/painting/imagecomposition/main.cpp 0
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*/
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