QwtRasterData Class Reference

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

#include <qwt_raster_data.h>

Inheritance diagram for QwtRasterData:

Public Types
enum	ConrecFlag { IgnoreAllVerticesOnLevel = 0x01, IgnoreOutOfRange = 0x02 }
	Flags to modify the contour algorithm. More...
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. More...
virtual void	initRaster (const QRectF &, const QSize &raster)
	Initialize a raster. More...
virtual void	discardRaster ()
	Discard a raster. More...
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

ConrecFlag

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

contourLines()

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/

discardRaster()

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()

initRaster()

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()

interval()

const QwtInterval & QwtRasterData::interval ( Qt::Axis  axis ) const

inline

Returns

Bounding interval for a axis

See also

setInterval

pixelHint()

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.

setInterval()

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.

value()

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.