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TQPicture Class Reference

The TQPicture class is a paint device that records and replays TQPainter commands. More...

#include <tqpicture.h>

Inherits TQPaintDevice.

List of all member functions.

Public Members

Protected Members

Related Functions

Detailed Description

The TQPicture class is a paint device that records and replays TQPainter 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.

TQt pictures use a proprietary binary format. Unlike native picture (meta-file) formats on many window systems, TQt 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.

TQPicture is an implicitly shared class.

Example of how to record a picture: 

    TQPicture  pic;
    TQPainter  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: 

    TQPicture  pic;
    pic.load( "drawing.pic" );     // load picture
    TQPainter  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

TQPicture::TQPicture ( int formatVersion = -1 )

Constructs an empty picture.

The formatVersion parameter may be used to create a TQPicture that can be read by applications that are compiled with earlier versions of TQt.

Note that the default formatVersion is -1 which signifies the current release, i.e. for TQt 3.1 a formatVersion of 5 is the same as the default formatVersion of -1.

Reading pictures generated by earlier versions of TQt is supported and needs no special coding; the format is automatically detected.

TQPicture::TQPicture ( const TQPicture & pic )

Constructs a shallow copy of pic.

TQPicture::~TQPicture ()

Destroys the picture.

TQRect TQPicture::boundingRect () const

Returns the picture's bounding rectangle or an invalid rectangle if the picture contains no data.

TQPicture TQPicture::copy () const [protected]

Returns a deep copy of the picture.

const char * TQPicture::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 TQPicture::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 TQPicture::isNull () const

Returns TRUE if the picture contains no data; otherwise returns FALSE.

bool TQPicture::load ( const TQString & 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 TQPicture 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 TQt XML module. The corresponding format string is "svg".

See also save().

Examples: picture/picture.cpp and xform/xform.cpp.

bool TQPicture::load ( TQIODevice * 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 TQPicture::metric ( int m ) const [virtual protected]

Internal implementation of the virtual TQPaintDevice::metric() function.

Use the TQPaintDeviceMetrics class instead.

A picture has the following hard-coded values: dpi=72, numcolors=16777216 and depth=24.

m is the metric to get.

TQPicture & TQPicture::operator= ( const TQPicture & p )

Assigns a shallow copy of p to this picture and returns a reference to this picture.

bool TQPicture::play ( TQPainter * painter )

Replays the picture using painter, and returns TRUE if successful; otherwise returns FALSE.

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

bool TQPicture::save ( const TQString & 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 TQPicture file format.

Currently, the only external format supported is the W3C SVG format which requires the TQt XML module. The corresponding format string is "svg".

See also load().

Example: picture/picture.cpp.

bool TQPicture::save ( TQIODevice * 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 TQPicture::setBoundingRect ( const TQRect & r )

Sets the picture's bounding rectangle to r. The automatically calculated value is overriden.

void TQPicture::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 TQPicture::size () const

Returns the size of the picture data.

See also data().

Related Functions

TQDataStream & operator<< ( TQDataStream & s, const TQPicture & r )

Writes picture r to the stream s and returns a reference to the stream.

TQDataStream & operator>> ( TQDataStream & s, TQPicture & r )

Reads a picture from the stream s into picture r and returns a reference to the stream.

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TQt 3.3.8