QPicture Class
The QPicture class is a paint device that records and replays QPainter commands. More...
| Header: | #include <QPicture> |
| CMake: | find_package(Qt6 REQUIRED COMPONENTS Gui)target_link_libraries(mytarget PRIVATE Qt6::Gui) |
| qmake: | QT += gui |
| Inherits: | QPaintDevice |
- List of all members, including inherited members
- QPicture is part of Implicitly Shared Classes.
Public Functions
| QPicture(int formatVersion = -1) | |
| QPicture(const QPicture &pic) | |
| virtual | ~QPicture() |
| QRect | boundingRect() const |
| const char * | data() const |
| bool | isNull() const |
| bool | load(const QString &fileName) |
| bool | load(QIODevice *dev) |
| bool | play(QPainter *painter) |
| bool | save(const QString &fileName) |
| bool | save(QIODevice *dev) |
| void | setBoundingRect(const QRect &r) |
| virtual void | setData(const char *data, uint size) |
| uint | size() const |
| void | swap(QPicture &other) |
| QPicture & | operator=(QPicture &&other) |
| QPicture & | operator=(const QPicture &p) |
Related Non-Members
| QDataStream & | operator<<(QDataStream &s, const QPicture &r) |
| QDataStream & | operator>>(QDataStream &s, QPicture &r) |
Detailed Description
A picture serializes painter commands to an IO device in a platform-independent format. They are sometimes referred to as meta-files.
Qt pictures use a proprietary binary format. Unlike native picture (meta-file) formats on many window systems, Qt pictures have no limitations regarding their contents. Everything that can be painted on a widget or pixmap (e.g., fonts, pixmaps, regions, transformed graphics, etc.) can also be stored in a picture.
QPicture is resolution independent, i.e. a QPicture can be displayed on different devices (for example svg, pdf, ps, printer and screen) looking the same. This is, for instance, needed for WYSIWYG print preview. QPicture runs in the default system dpi, and scales the painter to match differences in resolution depending on the window system.
Example of how to record a picture:
QPicture picture; QPainter painter; painter.begin(&picture); // paint in picture painter.drawEllipse(10,20, 80,70); // draw an ellipse painter.end(); // painting done picture.save("drawing.pic"); // save picture
Note that the list of painter commands is reset on each call to the QPainter::begin() function.
Example of how to replay a picture:
QPicture picture; picture.load("drawing.pic"); // load picture QPainter painter; painter.begin(&myImage); // paint in myImage painter.drawPicture(0, 0, picture); // draw the picture at (0,0) painter.end(); // painting done
Pictures can also be drawn using play(). Some basic data about a picture is available, for example, size(), isNull() and boundingRect().
See also QMovie.
Member Function Documentation
[explicit] QPicture::QPicture(int formatVersion = -1)
Constructs an empty picture.
The formatVersion parameter may be used to create a QPicture that can be read by applications that are compiled with earlier versions of Qt.
Note that the default formatVersion is -1 which signifies the current release, i.e. for Qt 4.0 a formatVersion of 7 is the same as the default formatVersion of -1.
Reading pictures generated by earlier versions of Qt is not supported in Qt 4.0.
QPicture::QPicture(const QPicture &pic)
Constructs a copy of pic.
This constructor is fast thanks to implicit sharing.
[virtual noexcept] QPicture::~QPicture()
Destroys the picture.
QRect QPicture::boundingRect() const
Returns the picture's bounding rectangle or an invalid rectangle if the picture contains no data.
See also setBoundingRect().
const char *QPicture::data() const
Returns a pointer to the picture data. The pointer is only valid until the next non-const function is called on this picture. The returned pointer is 0 if the picture contains no data.
See also setData(), size(), and isNull().
bool QPicture::isNull() const
Returns true if the picture contains no data; otherwise returns false.
bool QPicture::load(const QString &fileName)
Loads a picture from the file specified by fileName and returns true if successful; otherwise invalidates the picture and returns false.
See also save().
bool QPicture::load(QIODevice *dev)
This is an overloaded function.
dev is the device to use for loading.
bool QPicture::play(QPainter *painter)
Replays the picture using painter, and returns true if successful; otherwise returns false.
This function does exactly the same as QPainter::drawPicture() with (x, y) = (0, 0).
Note: The state of the painter isn't preserved by this function.
bool QPicture::save(const QString &fileName)
Saves a picture to the file specified by fileName and returns true if successful; otherwise returns false.
See also load().
bool QPicture::save(QIODevice *dev)
This is an overloaded function.
dev is the device to use for saving.
void QPicture::setBoundingRect(const QRect &r)
Sets the picture's bounding rectangle to r. The automatically calculated value is overridden.
See also boundingRect().
[virtual] void QPicture::setData(const char *data, uint size)
Sets the picture data directly from data and size. This function copies the input data.
uint QPicture::size() const
Returns the size of the picture data.
See also data().
[noexcept] void QPicture::swap(QPicture &other)
Swaps picture other with this picture. This operation is very fast and never fails.
[noexcept] QPicture &QPicture::operator=(QPicture &&other)
Move-assigns other to this QPicture instance.
QPicture &QPicture::operator=(const QPicture &p)
Assigns picture p to this picture and returns a reference to this picture.
Related Non-Members
QDataStream &operator<<(QDataStream &s, const QPicture &r)
Writes picture r to the stream s and returns a reference to the stream.
QDataStream &operator>>(QDataStream &s, QPicture &r)
Reads a picture from the stream s into picture r and returns a reference to the stream.