Man page - qwtmatrixrasterdata(3)

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Manual

QwtMatrixRasterData

NAME

QwtMatrixRasterData - A class representing a matrix of values as raster data.

SYNOPSIS

#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 ()
Constructor.
virtual ˜QwtMatrixRasterData ()
Destructor.
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;.

Enumerator
NearestNeighbour

Return the value from the matrix, that is nearest to the the requested position.

BilinearInterpolation

Interpolate the value from the distances and values of the 4 surrounding values in the matrix,

Member Function Documentation

int QwtMatrixRasterData::numColumns () const

Returns:

Number of columns of the value matrix

See also:

valueMatrix() , numRows() , setValueMatrix()

int QwtMatrixRasterData::numRows () const

Returns:

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.

Parameters:

area Requested area, ignored

Returns:

Calculated hint

See also:

ResampleMode , setMatrix(), setInterval()

Reimplemented from QwtRasterData .

QwtMatrixRasterData::ResampleMode QwtMatrixRasterData::resampleMode ()const

Returns:

resampling algorithm

See also:

setResampleMode() , value()

void QwtMatrixRasterData::setInterval (Qt::Axis axis, 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 )

Parameters:

axis X, Y or Z axis
interval Interval

See also:

QwtRasterData::interval() , setValueMatrix()

Reimplemented from QwtRasterData .

void QwtMatrixRasterData::setResampleMode (ResampleMode mode)

Set the resampling algorithm.

Parameters:

mode Resampling mode

See also:

resampleMode() , value()

void QwtMatrixRasterData::setValue (int row, int col, double value)

Change a single value in the matrix.

Parameters:

row Row index
col Column index
value New value

See also:

value() , setValueMatrix()

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

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.

Parameters:

values Vector of values
numColumns Number of columns

See also:

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

double QwtMatrixRasterData::value (double x, double y) const [virtual]

Returns:

the value at a raster position

Parameters:

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

See also:

ResampleMode

Implements QwtRasterData .

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

Returns:

Value matrix

See also:

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

Author

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