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

#include <qwt_raster_data.h>

Inheritance diagram for QwtRasterData:

Classes
class	ContourPlane

class	PrivateData

Public Types
enum	Attribute { WithoutGaps = 0x01 }
	Raster data attributes. More...

enum	ConrecFlag { IgnoreAllVerticesOnLevel = 0x01 , IgnoreOutOfRange = 0x02 }
	Flags to modify the contour algorithm. More...

typedef QMap< double, QPolygonF >	ContourLines
	Contour lines.

Public Member Functions
	QwtRasterData ()
	Constructor.

virtual	~QwtRasterData ()
	Destructor.

void	setAttribute (Attribute, bool on=true)
	Specify an attribute of the data.

bool	testAttribute (Attribute) const

virtual QwtInterval	interval (Qt::Axis) const =0

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
	Calculate contour lines.

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.

Gaps inside the bounding rectangle of the data can be indicated by NaN values ( when WithoutGaps is disabled ).

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 ).

QwtMatrixRasterData implements raster data, that returns values from a given 2D matrix.

See also: QwtMatrixRasterData

Member Enumeration Documentation

◆ Attribute

enum QwtRasterData::Attribute

Raster data attributes.

Additional information that is used to improve processing of the data.

Enumerator

WithoutGaps

The bounding rectangle of the data is spanned by the interval(Qt::XAxis) and interval(Qt::YAxis).

WithoutGaps indicates, that the data has no gaps ( unknown values ) in this area and the result of value() does not need to be checked for NaN values.

Enabling this flag will have an positive effect on the performance of rendering a QwtPlotSpectrogram.

The default setting is false.

Note: NaN values indicate an undefined value

◆ 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()

virtual QwtInterval QwtRasterData::interval ( Qt::Axis ) const

pure virtual

Returns: Bounding interval for an axis

See also: setInterval

Implemented in QwtGridRasterData, and QwtMatrixRasterData.

◆ 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 QwtGridRasterData, and QwtMatrixRasterData.

◆ setAttribute()

void QwtRasterData::setAttribute	(	Attribute	attribute,
		bool	on = `true`
	)

Specify an attribute of the data.

Parameters

attribute	Attribute
on	On/Off /sa Attribute, testAttribute()

◆ testAttribute()

bool QwtRasterData::testAttribute ( Attribute attribute ) const

Returns: True, when attribute is enabled

See also: Attribute, setAttribute()

◆ 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 QwtGridRasterData, and QwtMatrixRasterData.

The documentation for this class was generated from the following files:

/home/runner/work/QWT/QWT/src/qwt_raster_data.h
/home/runner/work/QWT/QWT/src/qwt_raster_data.cpp

Classes

Public Types

Public Member Functions

Detailed Description

Member Enumeration Documentation

◆ Attribute

◆ ConrecFlag

Member Function Documentation

◆ contourLines()

◆ discardRaster()

◆ initRaster()

◆ interval()

◆ pixelHint()

◆ setAttribute()

◆ testAttribute()

◆ value()