Qwt User's Guide: QwtColorMap Class Reference

Qwt User's Guide 6.1.6

Public Types | Public Member Functions | List of all members
QwtColorMap Class Referenceabstract

QwtColorMap is used to map values into colors. More...

`#include <qwt_color_map.h>`

Inheritance diagram for QwtColorMap:
[legend]

## Public Types
enum | Format { RGB, Indexed }

## Public Member Functions
| QwtColorMap (Format=QwtColorMap::RGB)
| Constructor.
virtual | ~QwtColorMap ()
| Destructor.
Format | format () const
virtual QRgb | rgb (const QwtInterval &interval, double value) const =0
virtual unsigned char | colorIndex (const QwtInterval &interval, double value) const =0
QColor | color (const QwtInterval &, double value) const
virtual QVector< QRgb > | colorTable (const QwtInterval &) 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

## ◆ Format

enum QwtColorMap::Format

Format for color mapping

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

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

## Member Function Documentation

## ◆ color()

QColor QwtColorMap::color | ( | const QwtInterval & | 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().

## ◆ colorIndex()

virtual unsigned char QwtColorMap::colorIndex | ( | const QwtInterval & | 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.

## ◆ colorTable()

QVector< QRgb > QwtColorMap::colorTable | ( | const QwtInterval & | 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

## ◆ format()

QwtColorMap::Format QwtColorMap::format | ( |  | ) | const
| inline

Returns
  Intended format of the color map

See also
  Format

## ◆ rgb()

virtual QRgb QwtColorMap::rgb | ( | const QwtInterval & | 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 QwtAlphaColorMap, and QwtLinearColorMap.