QwtColorMap(3)

NAME
QwtColorMap -

QwtColorMap is used to map values into colors.

SYNOPSIS

#include <qwt_color_map.h>

Inherited by QwtAlphaColorMap, and QwtLinearColorMap.

  Public Types
enum Format { RGB, Indexed }

  Public Member Functions
QwtColorMap (Format=QwtColorMap::RGB)
virtual ~QwtColorMap ()
Format format () const
virtual QwtColorMap * copy () const =0
virtual QRgb rgb (const QwtDoubleInterval &interval, double value) const =0
virtual unsigned char colorIndex (const QwtDoubleInterval &interval, double value) const =0
QColor color (const QwtDoubleInterval &, double value) const
virtual QVector< QRgb > colorTable (const QwtDoubleInterval &) const

Detailed Description

QwtColorMap is used to map values into colors. For displaying 3D data on a 2D plane the 3rd dimension is often displayed using colors, like f.e in a spectrogram.

Each color map is optimized to return colors for only one of the following image formats:

•   QImage::Format_Indexed8

•   QImage::Format_ARGB32

See also:
    QwtPlotSpectrogram, QwtScaleWidget

Member Enumeration Documentation

  enum QwtColorMap::Format .IP • 2
RGB
 The map is intended to map into QRgb values.

•   Indexed
     The map is intended to map into 8 bit values, that are indices into the color table.

See also:
    rgb(), colorIndex(), colorTable()

Constructor & Destructor Documentation

  QwtColorMap::QwtColorMap (Format format = QwtColorMap::RGB)

Constructor.

  QwtColorMap::~QwtColorMap () [virtual]

Destructor.

Member Function Documentation

  QColor QwtColorMap::color (const QwtDoubleInterval & interval, double value) const [inline] Map a value into a color

Parameters:
    interval Valid interval for values
    value Value

Returns:
    Color corresponding to value

Warning:
    This method is slow for Indexed color maps. If it is necessary to map many values, its better to get the color table once and find the color using colorIndex().

  virtual unsigned char QwtColorMap::colorIndex (const QwtDoubleInterval & interval, double value) const [pure virtual] Map a value of a given interval into a color index

Parameters:
    interval Range for the values
    value Value

Returns:
    color index, corresponding to value

Implemented in QwtLinearColorMap.

  QwtColorTable QwtColorMap::colorTable (const QwtDoubleInterval & interval) const [virtual] Build and return a color map of 256 colors

The color table is needed for rendering indexed images in combination with using colorIndex().

Parameters:
    interval Range for the values

Returns:
    A color table, that can be used for a QImage

  virtual QwtColorMap* QwtColorMap::copy () const [pure virtual]

Clone the color map.

Implemented in QwtLinearColorMap, and QwtAlphaColorMap.

  QwtColorMap::Format QwtColorMap::format () const [inline] Returns:
    Intended format of the color map

See also:
    Format

  virtual QRgb QwtColorMap::rgb (const QwtDoubleInterval & interval, double value) const [pure virtual] Map a value of a given interval into a rgb value.

Parameters:
    interval Range for the values
    value Value

Returns:
    rgb value, corresponding to value

Implemented in QwtLinearColorMap, and QwtAlphaColorMap.

Author

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