Qwt User's Guide: QwtRasterData Class Reference

Qwt User's Guide 5.2.3

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Public Types | Public Member Functions
QwtRasterData Class Reference

`#include <qwt_raster_data.h>`

Inheritance diagram for QwtRasterData:
[legend]

List of all members.

## 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,
|  | int | flags
| ) |  | 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 | ( | 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