QwtMatrixRasterData(3) A class representing a matrix of values as raster data.


#include <qwt_matrix_raster_data.h>

Inherits QwtRasterData.

Public Types

enum ResampleMode { NearestNeighbour, BilinearInterpolation }
Resampling algorithm The default setting is NearestNeighbour;.

Public Member Functions

QwtMatrixRasterData ()
virtual ~QwtMatrixRasterData ()
void setResampleMode (ResampleMode mode)
Set the resampling algorithm.
ResampleMode resampleMode () const

virtual void setInterval (Qt::Axis, const QwtInterval &)
Assign the bounding interval for an axis.
void setValueMatrix (const QVector< double > &values, int numColumns)
Assign a value matrix.
const QVector< double > valueMatrix () const

void setValue (int row, int col, double value)
Change a single value in the matrix.
int numColumns () const

int numRows () const

virtual QRectF pixelHint (const QRectF &) const
Calculate the pixel hint.
virtual double value (double x, double y) const

Detailed Description

A class representing a matrix of values as raster data.

QwtMatrixRasterData implements an interface for a matrix of equidistant values, that can be used by a QwtPlotRasterItem. It implements a couple of resampling algorithms, to provide values for positions, that or not on the value matrix.

Member Enumeration Documentation

enum QwtMatrixRasterData::ResampleMode

Resampling algorithm The default setting is NearestNeighbour;.


Return the value from the matrix, that is nearest to the the requested position.
Interpolate the value from the distances and values of the 4 surrounding values in the matrix,

Member Function Documentation

int QwtMatrixRasterData::numColumns () const


Number of columns of the value matrix

See Also:

valueMatrix(), numRows(), setValueMatrix()

int QwtMatrixRasterData::numRows () const


Number of rows of the value matrix

See Also:

valueMatrix(), numColumns(), setValueMatrix()

QRectF QwtMatrixRasterData::pixelHint (const QRectF &area) const [virtual]

Calculate the 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.

  • NearestNeighbour

     pixelHint() returns the surrounding pixel of the top left value in the matrix.
  • BilinearInterpolation

     Returns an empty rectangle recommending to render in target device ( f.e. screen ) resolution.


area Requested area, ignored


Calculated hint

See Also:

ResampleMode, setMatrix(), setInterval()

Reimplemented from QwtRasterData.

QwtMatrixRasterData::ResampleMode QwtMatrixRasterData::resampleMode () const


resampling algorithm

See Also:

setResampleMode(), value()

void QwtMatrixRasterData::setInterval (Qt::Axisaxis, const QwtInterval &interval) [virtual]

Assign the bounding interval for an axis. Setting the bounding intervals for the X/Y axis is mandatory to define the positions for the values of the value matrix. The interval in Z direction defines the possible range for the values in the matrix, what is f.e used by QwtPlotSpectrogram to map values to colors. The Z-interval might be the bounding interval of the values in the matrix, but usually it isn't. ( f.e a interval of 0.0-100.0 for values in percentage )


axis X, Y or Z axis
interval Interval

See Also:

QwtRasterData::interval(), setValueMatrix()

Reimplemented from QwtRasterData.

void QwtMatrixRasterData::setResampleMode (ResampleModemode)

Set the resampling algorithm.


mode Resampling mode

See Also:

resampleMode(), value()

void QwtMatrixRasterData::setValue (introw, intcol, doublevalue)

Change a single value in the matrix.


row Row index
col Column index
value New value

See Also:

value(), setValueMatrix()

void QwtMatrixRasterData::setValueMatrix (const QVector< double > &values, intnumColumns)

Assign a value matrix. The positions of the values are calculated by dividing the bounding rectangle of the X/Y intervals into equidistant rectangles ( pixels ). Each value corresponds to the center of a pixel.


values Vector of values
numColumns Number of columns

See Also:

valueMatrix(), numColumns(), numRows(), setInterval()()

double QwtMatrixRasterData::value (doublex, doubley) const [virtual]


the value at a raster position


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

See Also:


Implements QwtRasterData.

const QVector< double > QwtMatrixRasterData::valueMatrix () const


Value matrix

See Also:

setValueMatrix(), numColumns(), numRows(), setInterval()


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