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41
42/*!
43 \example painting/imagecomposition
44 \title Image Composition Example
45
46 The Image Composition example lets the user combine images
47 together using any composition mode supported by QPainter, described
48 in detail in \l{QPainter#Composition Modes}{Composition Modes}.
49
50 \image imagecomposition-example.png
51
52 \section1 Setting Up The Resource File
53
54 The Image Composition example requires two source images,
55 \e butterfly.png and \e checker.png that are embedded within
56 \e imagecomposition.qrc. The file contains the following code:
57
58 \quotefile examples/painting/imagecomposition/imagecomposition.qrc
59
60 For more information on resource files, see \l{The Qt Resource System}.
61
62 \section1 ImageComposer Class Definition
63
64 The \c ImageComposer class is a subclass of QWidget that implements three
65 private slots, \c chooseSource(), \c chooseDestination(), and
66 \c recalculateResult().
67
68 \snippet examples/painting/imagecomposition/imagecomposer.h 0
69
70 In addition, \c ImageComposer consists of five private functions,
71 \c addOp(), \c chooseImage(), \c loadImage(), \c currentMode(), and
72 \c imagePos(), as well as private instances of QToolButton, QComboBox,
73 QLabel, and QImage.
74
75 \snippet examples/painting/imagecomposition/imagecomposer.h 1
76
77 \section1 ImageComposer Class Implementation
78
79 We declare a QSize object, \c resultSize, as a static constant with width
80 and height equal to 200.
81
82 \snippet examples/painting/imagecomposition/imagecomposer.cpp 0
83
84 Within the constructor, we instantiate a QToolButton object,
85 \c sourceButton and set its \l{QAbstractButton::setIconSize()}{iconSize}
86 property to \c resultSize. The \c operatorComboBox is instantiated and
87 then populated using the \c addOp() function. This function accepts a
88 QPainter::CompositionMode, \a mode, and a QString, \a name, representing
89 the name of the composition mode.
90
91 \snippet examples/painting/imagecomposition/imagecomposer.cpp 1
92
93 The \c destinationButton is instantiated and its
94 \l{QAbstractButton::setIconSize()}{iconSize} property is set to
95 \c resultSize as well. The \l{QLabel}s \c equalLabel and \c resultLabel
96 are created and \c{resultLabel}'s \l{QWidget::setMinimumWidth()}
97 {minimumWidth} is set.
98
99 \snippet examples/painting/imagecomposition/imagecomposer.cpp 2
100
101 We connect the following signals to their corresponding slots:
102 \list
103 \o \c{sourceButton}'s \l{QPushButton::clicked()}{clicked()} signal is
104 connected to \c chooseSource(),
105 \o \c{operatorComboBox}'s \l{QComboBox::activated()}{activated()}
106 signal is connected to \c recalculateResult(), and
107 \o \c{destinationButton}'s \l{QToolButton::clicked()}{clicked()} signal
108 is connected to \c chooseDestination().
109 \endlist
110
111 \snippet examples/painting/imagecomposition/imagecomposer.cpp 3
112
113 A QGridLayout, \c mainLayout, is used to place all the widgets. Note
114 that \c{mainLayout}'s \l{QLayout::setSizeConstraint()}{sizeConstraint}
115 property is set to QLayout::SetFixedSize, which means that
116 \c{ImageComposer}'s size cannot be resized at all.
117
118 \snippet examples/painting/imagecomposition/imagecomposer.cpp 4
119
120 We create a QImage, \c resultImage, and we invoke \c loadImage() twice
121 to load both the image files in our \e imagecomposition.qrc file. Then,
122 we set the \l{QWidget::setWindowTitle()}{windowTitle} property to
123 "Image Composition".
124
125 \snippet examples/painting/imagecomposition/imagecomposer.cpp 5
126
127 The \c chooseSource() and \c chooseDestination() functions are
128 convenience functions that invoke \c chooseImage() with specific
129 parameters.
130
131 \snippet examples/painting/imagecomposition/imagecomposer.cpp 6
132 \codeline
133 \snippet examples/painting/imagecomposition/imagecomposer.cpp 7
134
135 The \c chooseImage() function loads an image of the user's choice,
136 depending on the \a title, \a image, and \a button.
137
138 \snippet examples/painting/imagecomposition/imagecomposer.cpp 10
139
140 The \c recalculateResult() function is used to calculate amd display the
141 result of combining the two images together with the user's choice of
142 composition mode.
143
144 \snippet examples/painting/imagecomposition/imagecomposer.cpp 8
145
146 The \c addOp() function adds an item to the \c operatorComboBox using
147 \l{QComboBox}'s \l{QComboBox::addItem()}{addItem} function. This function
148 accepts a QPainter::CompositionMode, \a mode, and a QString, \a name. The
149 rectangle is filled with Qt::Transparent and both the \c sourceImage and
150 \c destinationImage are painted, before displaying it on \c resultLabel.
151
152 \snippet examples/painting/imagecomposition/imagecomposer.cpp 9
153
154 The \c loadImage() function paints a transparent background using
155 \l{QPainter::fillRect()}{fillRect()} and draws \c image in a
156 centralized position using \l{QPainter::drawImage()}{drawImage()}.
157 This \c image is then set as the \c{button}'s icon.
158
159 \snippet examples/painting/imagecomposition/imagecomposer.cpp 11
160
161 The \c currentMode() function returns the composition mode currently
162 selected in \c operatorComboBox.
163
164 \snippet examples/painting/imagecomposition/imagecomposer.cpp 12
165
166 We use the \c imagePos() function to ensure that images loaded onto the
167 QToolButton objects, \c sourceButton and \c destinationButton, are
168 centralized.
169
170 \snippet examples/painting/imagecomposition/imagecomposer.cpp 13
171
172 \section1 The \c main() Function
173
174 The \c main() function instantiates QApplication and \c ImageComposer
175 and invokes its \l{QWidget::show()}{show()} function.
176
177 \snippet examples/painting/imagecomposition/main.cpp 0
178
179 */
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