The QPicture class is a paint device that records and
replays QPainter commands.
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Detailed Description
The QPicture class is a paint device that records and
replays QPainter commands.
A picture serializes painter commands to an IO device in a
platform-independent format. For example, a picture created under
Windows can be read on a Sun SPARC.
Pictures are called meta-files on some platforms.
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 can also be stored in a picture, e.g. fonts, pixmaps,
regions, transformed graphics, etc.
QPicture is an implicitly shared class.
Example of how to record a picture:
QPicture pic;
QPainter p;
p.begin( &pic ); // paint in picture
p.drawEllipse( 10,20, 80,70 ); // draw an ellipse
p.end(); // painting done
pic.save( "drawing.pic" ); // save picture
Example of how to replay a picture:
QPicture pic;
pic.load( "drawing.pic" ); // load picture
QPainter p;
p.begin( &myWidget ); // paint in myWidget
p.drawPicture( pic ); // draw the picture
p.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 Graphics Classes, Image Processing Classes, and Implicitly and Explicitly Shared Classes.
Member Function Documentation
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.
- formatVersion == 1 is binary compatible with Qt 1.x and later.
- formatVersion == 2 is binary compatible with Qt 2.0.x and later.
- formatVersion == 3 is binary compatible with Qt 2.1.x and later.
- formatVersion == 4 is binary compatible with Qt 3.0.x and later.
- formatVersion == 5 is binary compatible with Qt 3.1.
Note that the default formatVersion is -1 which signifies the
current release, i.e. for Qt 3.1 a formatVersion of 5 is the same
as the default formatVersion of -1.
Reading pictures generated by earlier versions of Qt is supported
and needs no special coding; the format is automatically detected.
QPicture::QPicture ( const QPicture & pic )
Constructs a shallow copy of pic.
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.
QPicture QPicture::copy () const [protected]
Returns a deep copy of the picture.
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 size() and isNull().
void QPicture::detach () [protected]
Detaches from shared picture data and makes sure that this picture
is the only one referring to the data.
If multiple pictures share common data, this picture makes a copy
of the data and detaches itself from the sharing mechanism.
Nothing is done if there is just a single reference.
bool QPicture::isNull () const
Returns TRUE if the picture contains no data; otherwise returns
FALSE.
bool QPicture::load ( const QString & fileName, const char * format = 0 )
Loads a picture from the file specified by fileName and returns
TRUE if successful; otherwise returns FALSE.
By default, the file will be interpreted as being in the native
QPicture format. Specifying the format string is optional and
is only needed for importing picture data stored in a different
format.
Currently, the only external format supported is the W3C SVG format which
requires the Qt XML module. The
corresponding format string is "svg".
See also save().
Examples: picture/picture.cpp and xform/xform.cpp.
bool QPicture::load ( QIODevice * dev, const char * format = 0 )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
dev is the device to use for loading.
int QPicture::metric ( int m ) const [virtual protected]
Internal implementation of the virtual QPaintDevice::metric()
function.
Use the QPaintDeviceMetrics class instead.
A picture has the following hard-coded values: dpi=72,
numcolors=16777216 and depth=24.
m is the metric to get.
QPicture & QPicture::operator= ( const QPicture & p )
Assigns a shallow copy of p to this
picture and returns a reference to this picture.
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).
bool QPicture::save ( const QString & fileName, const char * format = 0 )
Saves a picture to the file specified by fileName and returns
TRUE if successful; otherwise returns FALSE.
Specifying the file format string is optional. It's not
recommended unless you intend to export the picture data for
use by a third party reader. By default the data will be saved in
the native QPicture file format.
Currently, the only external format supported is the W3C SVG format which
requires the Qt XML module. The
corresponding format string is "svg".
See also load().
Example: picture/picture.cpp.
bool QPicture::save ( QIODevice * dev, const char * format = 0 )
This is an overloaded member function, provided for convenience. It behaves essentially like the above 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 overriden.
void QPicture::setData ( const char * data, uint size ) [virtual]
Sets the picture data directly from data and size. This
function copies the input data.
See also data() and size().
uint QPicture::size () const
Returns the size of the picture data.
See also data().
Related Functions
Writes picture r to the stream s and returns a reference to
the stream.
Reads a picture from the stream s into picture r and returns
a reference to the stream.
This file is part of the Qt toolkit.
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