QPicture Class

Qt 3.0.5

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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
  • QPicture & operator= ( const QPicture & p )

Protected Members

Related Functions

  • QDataStream & operator<< ( QDataStream & s, const QPicture & r )
  • QDataStream & operator>> ( QDataStream & s, QPicture & r )

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.x.

Note that the default formatVersion is -1 which signifies the current release, i.e. for Qt 3.0 a formatVersion of 4 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::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

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.

This file is part of the Qt toolkit. Copyright © 1995-2002 Trolltech. All Rights Reserved.

Copyright © 2002 TrolltechTrademarks
Qt version 3.0.5

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