NAME

       QwtRasterData - QwtRasterData defines an interface to any type of raster data.

SYNOPSIS

       #include <qwt_raster_data.h>

       Inherited by QwtMatrixRasterData.

   Public Types
       enum ConrecFlag { IgnoreAllVerticesOnLevel = 0x01, IgnoreOutOfRange = 0x02 }
           Flags to modify the contour algorithm.
       typedef QMap< double, QPolygonF > ContourLines
           Contour lines.
       typedef QFlags< ConrecFlag > ConrecFlags
           Flags to modify the contour algorithm.

   Public Member Functions
       QwtRasterData ()
           Constructor.
       virtual ~QwtRasterData ()
           Destructor.
       virtual void setInterval (Qt::Axis, const QwtInterval &)
       const QwtInterval & interval (Qt::Axis) const
       virtual QRectF pixelHint (const QRectF &) const
           Pixel hint.
       virtual void initRaster (const QRectF &, const QSize &raster)
           Initialize a raster.
       virtual void discardRaster ()
           Discard a raster.
       virtual double value (double x, double y) const =0
       virtual ContourLines contourLines (const QRectF &rect, const QSize &raster, const QList<
           double > &levels, ConrecFlags) const

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
       ).

Member Enumeration Documentation

   enum QwtRasterData::ConrecFlag
       Flags to modify the contour algorithm.

       Enumerator

       IgnoreAllVerticesOnLevel
              Ignore all vertices on the same level.

       IgnoreOutOfRange
              Ignore all values, that are out of range.

Member Function Documentation

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

       Parameters:
           rect Bounding rectangle for the contour lines
           raster Number of data pixels of the raster data
           levels List of limits, where to insert contour lines
           flags Flags to customize the contouring algorithm

       Returns:
           Calculated 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 QRectF & area, 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:
           area Area of the raster
           raster Number of horizontal and vertical pixels

       See also:
           initRaster(), value()

   const QwtInterval & QwtRasterData::interval (Qt::Axis axis) const [inline]
       Returns:
           Bounding interval for a axis

       See also:
           setInterval

   QRectF QwtRasterData::pixelHint (const QRectF & area) const [virtual]
       Pixel hint. pixelHint() returns the geometry of a pixel, that can be used to calculate the
       resolution and alignment of the plot item, that is representing the data.

       Width and height of the hint need to be the horizontal and vertical distances between 2
       neighbored points. The center of the hint has to be the position of any point ( it doesn't
       matter which one ).

       An empty hint indicates, that there are values for any detail level.

       Limiting the resolution of the image might significantly improve the performance and
       heavily reduce the amount of memory when rendering a QImage from the raster data.

       The default implementation returns an empty rectangle recommending to render in target
       device ( f.e. screen ) resolution.

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

       Returns:
           Bounding rectangle of a pixel

       Reimplemented in QwtMatrixRasterData.

   void QwtRasterData::setInterval (Qt::Axis axis, const QwtInterval & interval) [virtual]
       Set the bounding interval for the x, y or z coordinates.

       Parameters:
           axis Axis
           interval Bounding interval

       See also:
           interval()

       Reimplemented in QwtMatrixRasterData.

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

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

       Implemented in QwtMatrixRasterData.

Author

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