NAME

       QwtRasterData -

SYNOPSIS

       #include <qwt_raster_data.h>

       Inherited by QwtPlotSpectrogram::PrivateData::DummyData.

   Public Types
       enum ConrecAttribute { IgnoreAllVerticesOnLevel =  1, IgnoreOutOfRange =  2 }
       typedef QMap< double, QPolygonF > ContourLines

   Public Member Functions
       QwtRasterData ()
       QwtRasterData (const QwtDoubleRect &)
       virtual ~QwtRasterData ()
       QwtDoubleRect boundingRect () const
       virtual ContourLines contourLines (const QwtDoubleRect &rect, const QSize &raster, const
           QList< double > &levels, int flags) const
       virtual QwtRasterData * copy () const =0
       virtual void discardRaster ()
       virtual void initRaster (const QwtDoubleRect &, const QSize &raster)
       virtual QwtDoubleInterval range () const =0
       virtual QSize rasterHint (const QwtDoubleRect &) const
       virtual void setBoundingRect (const QwtDoubleRect &)
       virtual double value (double x, double y) const =0

Detailed Description

       QwtRasterData defines an interface to any type of raster data.

       QwtRasterData is an abstract interface, that is used by QwtPlotRasterItem to find the
       values at the pixels of its raster.

       Often a raster item is used to display values from a matrix. Then the derived raster data
       class needs to implement some sort of resampling, that maps the raster of the matrix into
       the requested raster of the raster item ( depending on resolution and scales of the canvas
       ).

Constructor & Destructor Documentation

   QwtRasterData::QwtRasterData (const QwtDoubleRect &boundingRect)
       Constructor

       Parameters:
           boundingRect Bounding rectangle

       See also:
           setBoundingRect()

Member Function Documentation

   QwtDoubleRect QwtRasterData::boundingRect () const
       Returns:
           Bounding rectangle

       See also:
           boundingRect()

   QwtRasterData::ContourLines QwtRasterData::contourLines (const QwtDoubleRect &rect, const
       QSize &raster, const QList< double > &levels, intflags) const [virtual]
       Calculate contour lines

       An adaption of CONREC, a simple contouring algorithm.
       http://local.wasp.uwa.edu.au/~pbourke/papers/conrec/

   void QwtRasterData::discardRaster () [virtual]
       Discard a raster. After the composition of an image QwtPlotSpectrogram calls
       discardRaster().

       The default implementation does nothing, but if data has been loaded in initRaster(), it
       could deleted now.

       See also:
           initRaster(), value()

   void QwtRasterData::initRaster (const QwtDoubleRect &, const QSize &raster) [virtual]
       Initialize a raster. Before the composition of an image QwtPlotSpectrogram calls
       initRaster, announcing the area and its resolution that will be requested.

       The default implementation does nothing, but for data sets that are stored in files, it
       might be good idea to reimplement initRaster, where the data is resampled and loaded into
       memory.

       Parameters:
           rect Area of the raster
           raster Number of horizontal and vertical pixels

       See also:
           initRaster(), value()

   virtual QwtDoubleInterval QwtRasterData::range () const [pure virtual]
       Returns:
           the range of the values

   QSize QwtRasterData::rasterHint (const QwtDoubleRect &) const [virtual]
       Find the raster of the data for an area. The resolution is the number of horizontal and
       vertical pixels that the data can return for an area. An invalid resolution indicates that
       the data can return values for any detail level.

       The resolution will limit the size of the image that is rendered from the data. F.e. this
       might be important when printing a spectrogram to a A0 printer with 600 dpi.

       The default implementation returns an invalid resolution (size)

       Parameters:
           rect In most implementations the resolution of the data doesn't depend on the
           requested rectangle.

       Returns:
           Resolution, as number of horizontal and vertical pixels

   void QwtRasterData::setBoundingRect (const QwtDoubleRect &boundingRect) [virtual]
       Set the bounding rect ( == area, un plot coordinates )

       Parameters:
           boundingRect Bounding rectangle

       See also:
           boundingRect()

   virtual double QwtRasterData::value (doublex, doubley) const [pure virtual]
       Returns:
           the value at a raster position

       Parameters:
           x X value in plot coordinates
           y Y value in plot coordinates

Author

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