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QPicture Class Reference

The QPicture class is a paint device that records and replays QPainter commands. More...

#include <qpicture.h>

Inherits QPaintDevice.

List of all member functions.

Public Members

• QPicture ( int formatVersion = -1 )
• QPicture ( const QPicture & pic )
• ~QPicture ()
• bool isNull () const
• uint size () const
• const char * data () const
• virtual void setData ( const char * data, uint size )
• bool play ( QPainter * painter )
• bool load ( QIODevice * dev, const char * format = 0 )
• bool load ( const QString & fileName, const char * format = 0 )
• bool save ( QIODevice * dev, const char * format = 0 )
• bool save ( const QString & fileName, const char * format = 0 )
• QRect boundingRect () const
• void setBoundingRect ( const QRect & r )
• QPicture & operator= ( const QPicture & p )

Protected Members

• virtual int metric ( int m ) const
• void detach ()
• QPicture copy () const

Related Functions

• 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. 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 )

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 )

QPicture::~QPicture ()

QRect QPicture::boundingRect () const

QPicture QPicture::copy () const [protected]

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]

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 )

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 )

dev is the device to use for loading.

int QPicture::metric ( int m ) const [virtual protected]

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 )

bool QPicture::play ( QPainter * painter )

This function does exactly the same as QPainter::drawPicture() with (x, y) = (0, 0).

bool QPicture::save ( const QString & fileName, const char * format = 0 )

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 )

dev is the device to use for saving.

void QPicture::setBoundingRect ( const QRect & r )

void QPicture::setData ( const char * data, uint size ) [virtual]

See also data() and size().

uint QPicture::size () const

Returns the size of the picture data.

See also data().

Related Functions

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.

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