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27
28/*!
29 \example painting/imagecomposition
30 \title Image Composition Example
31
32 The Image Composition example lets the user combine images
33 together using any composition mode supported by QPainter, described
34 in detail in \l{QPainter#Composition Modes}{Composition Modes}.
35
36 \image imagecomposition-example.png
37
38 \section1 Setting Up The Resource File
39
40 The Image Composition example requires two source images,
41 \e butterfly.png and \e checker.png that are embedded within
42 \e imagecomposition.qrc. The file contains the following code:
43
44 \quotefile examples/painting/imagecomposition/imagecomposition.qrc
45
46 For more information on resource files, see \l{The Qt Resource System}.
47
48 \section1 ImageComposer Class Definition
49
50 The \c ImageComposer class is a subclass of QWidget that implements three
51 private slots, \c chooseSource(), \c chooseDestination(), and
52 \c recalculateResult().
53
54 \snippet examples/painting/imagecomposition/imagecomposer.h 0
55
56 In addition, \c ImageComposer consists of five private functions,
57 \c addOp(), \c chooseImage(), \c loadImage(), \c currentMode(), and
58 \c imagePos(), as well as private instances of QToolButton, QComboBox,
59 QLabel, and QImage.
60
61 \snippet examples/painting/imagecomposition/imagecomposer.h 1
62
63 \section1 ImageComposer Class Implementation
64
65 We declare a QSize object, \c resultSize, as a static constant with width
66 and height equal to 200.
67
68 \snippet examples/painting/imagecomposition/imagecomposer.cpp 0
69
70 Within the constructor, we instantiate a QToolButton object,
71 \c sourceButton and set its \l{QAbstractButton::setIconSize()}{iconSize}
72 property to \c resultSize. The \c operatorComboBox is instantiated and
73 then populated using the \c addOp() function. This function accepts a
74 QPainter::CompositionMode, \a mode, and a QString, \a name, representing
75 the name of the composition mode.
76
77 \snippet examples/painting/imagecomposition/imagecomposer.cpp 1
78
79 The \c destinationButton is instantiated and its
80 \l{QAbstractButton::setIconSize()}{iconSize} property is set to
81 \c resultSize as well. The \l{QLabel}s \c equalLabel and \c resultLabel
82 are created and \c{resultLabel}'s \l{QWidget::setMinimumWidth()}
83 {minimumWidth} is set.
84
85 \snippet examples/painting/imagecomposition/imagecomposer.cpp 2
86
87 We connect the following signals to their corresponding slots:
88 \list
89 \o \c{sourceButton}'s \l{QPushButton::clicked()}{clicked()} signal is
90 connected to \c chooseSource(),
91 \o \c{operatorComboBox}'s \l{QComboBox::activated()}{activated()}
92 signal is connected to \c recalculateResult(), and
93 \o \c{destinationButton}'s \l{QToolButton::clicked()}{clicked()} signal
94 is connected to \c chooseDestination().
95 \endlist
96
97 \snippet examples/painting/imagecomposition/imagecomposer.cpp 3
98
99 A QGridLayout, \c mainLayout, is used to place all the widgets. Note
100 that \c{mainLayout}'s \l{QLayout::setSizeConstraint()}{sizeConstraint}
101 property is set to QLayout::SetFixedSize, which means that
102 \c{ImageComposer}'s size cannot be resized at all.
103
104 \snippet examples/painting/imagecomposition/imagecomposer.cpp 4
105
106 We create a QImage, \c resultImage, and we invoke \c loadImage() twice
107 to load both the image files in our \e imagecomposition.qrc file. Then,
108 we set the \l{QWidget::setWindowTitle()}{windowTitle} property to
109 "Image Composition".
110
111 \snippet examples/painting/imagecomposition/imagecomposer.cpp 5
112
113 The \c chooseSource() and \c chooseDestination() functions are
114 convenience functions that invoke \c chooseImage() with specific
115 parameters.
116
117 \snippet examples/painting/imagecomposition/imagecomposer.cpp 6
118 \codeline
119 \snippet examples/painting/imagecomposition/imagecomposer.cpp 7
120
121 The \c chooseImage() function loads an image of the user's choice,
122 depending on the \a title, \a image, and \a button.
123
124 \snippet examples/painting/imagecomposition/imagecomposer.cpp 10
125
126 The \c recalculateResult() function is used to calculate amd display the
127 result of combining the two images together with the user's choice of
128 composition mode.
129
130 \snippet examples/painting/imagecomposition/imagecomposer.cpp 8
131
132 The \c addOp() function adds an item to the \c operatorComboBox using
133 \l{QComboBox}'s \l{QComboBox::addItem()}{addItem} function. This function
134 accepts a QPainter::CompositionMode, \a mode, and a QString, \a name. The
135 rectangle is filled with Qt::Transparent and both the \c sourceImage and
136 \c destinationImage are painted, before displaying it on \c resultLabel.
137
138 \snippet examples/painting/imagecomposition/imagecomposer.cpp 9
139
140 The \c loadImage() function paints a transparent background using
141 \l{QPainter::fillRect()}{fillRect()} and draws \c image in a
142 centralized position using \l{QPainter::drawImage()}{drawImage()}.
143 This \c image is then set as the \c{button}'s icon.
144
145 \snippet examples/painting/imagecomposition/imagecomposer.cpp 11
146
147 The \c currentMode() function returns the composition mode currently
148 selected in \c operatorComboBox.
149
150 \snippet examples/painting/imagecomposition/imagecomposer.cpp 12
151
152 We use the \c imagePos() function to ensure that images loaded onto the
153 QToolButton objects, \c sourceButton and \c destinationButton, are
154 centralized.
155
156 \snippet examples/painting/imagecomposition/imagecomposer.cpp 13
157
158 \section1 The \c main() Function
159
160 The \c main() function instantiates QApplication and \c ImageComposer
161 and invokes its \l{QWidget::show()}{show()} function.
162
163 \snippet examples/painting/imagecomposition/main.cpp 0
164
165 */
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