Qwt User's Guide  6.0.2
Public Types | Public Member Functions
QwtRasterData Class Reference

#include <qwt_raster_data.h>

Inheritance diagram for QwtRasterData:
Inheritance graph
[legend]

List of all members.

Public Types

enum  ConrecFlag {
  IgnoreAllVerticesOnLevel = 0x01,
  IgnoreOutOfRange = 0x02
}
typedef QFlags< ConrecFlagConrecFlags
typedef QMap< double, QPolygonF > ContourLines

Public Member Functions

 QwtRasterData ()
virtual ~QwtRasterData ()
virtual ContourLines contourLines (const QRectF &rect, const QSize &raster, const QList< double > &levels, ConrecFlags) const
virtual void discardRaster ()
virtual void initRaster (const QRectF &, const QSize &raster)
const QwtIntervalinterval (Qt::Axis) const
virtual QRectF pixelHint (const QRectF &) const
virtual void setInterval (Qt::Axis, const QwtInterval &)
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 ).


Member Enumeration Documentation

Flags to modify the contour algorithm.

Enumerator:
IgnoreAllVerticesOnLevel 

Ignore all verices on the same level.

IgnoreOutOfRange 

Ignore all values, that are out of range.


Member Function Documentation

QwtRasterData::ContourLines QwtRasterData::contourLines ( const QRectF &  rect,
const QSize &  raster,
const QList< double > &  levels,
ConrecFlags  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 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:
areaArea of the raster
rasterNumber of horizontal and vertical pixels
See also:
initRaster(), value()
const QwtInterval & QwtRasterData::interval ( Qt::Axis  axis) const
inline
Returns:
Bounding interval for a axis
See also:
setInterval
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 neighboured 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:
areaIn most implementations the resolution of the data doesn't depend on the requested area.
Returns:
Bounding rectangle of a pixel

Reimplemented in QwtMatrixRasterData.

void QwtRasterData::setInterval ( Qt::Axis  axis,
const QwtInterval interval 
)
virtual

Set the bounding interval for the x, y or z coordinates.

Parameters:
axisAxis
intervalBounding interval
See also:
interval()

Reimplemented in QwtMatrixRasterData.

virtual double QwtRasterData::value ( double  x,
double  y 
) const
pure virtual
Returns:
the value at a raster position
Parameters:
xX value in plot coordinates
yY value in plot coordinates

Implemented in QwtMatrixRasterData.