Qwt User's Guide: QwtColorMap Class Reference

Qwt User's Guide 6.2.0

Public Types | Public Member Functions | Public Attributes | 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:

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

## Public Member Functions
| QwtColorMap (Format=QwtColorMap::RGB)
virtual | ~QwtColorMap ()
| Destructor.
void | setFormat (Format)
virtual QRgb | rgb (const QwtInterval &interval, double value) const =0
virtual uint | colorIndex (int numColors, const QwtInterval &interval, double value) const
| Map a value of a given interval into a color index. More...
QColor | color (const QwtInterval &, double value) const
virtual QVector< QRgb > | colorTable (int numColors) const
virtual QVector< QRgb > | colorTable256 () const

## Public Attributes
Format | 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

Definition at line 37 of file qwt_color_map.h.

## 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 | Map values into 8 bit values, that are used as indexes into the color table. Indexed color maps are used to generate QImage::Format_Indexed8 images. The calculation of the color index is usually faster and the resulting image has a lower memory footprint. See also colorIndex(), colorTable()

Definition at line 45 of file qwt_color_map.h.

## Constructor & Destructor Documentation

## ◆ QwtColorMap()

QwtColorMap::QwtColorMap | ( | Format | format = `QwtColorMap::RGB` | ) |
| explicit

Constructor

Parameters

  format | Format of the color map

Definition at line 249 of file qwt_color_map.cpp.

## 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

Definition at line 248 of file qwt_color_map.h.

## ◆ colorIndex()

uint QwtColorMap::colorIndex | ( | int | numColors,
|  | const QwtInterval & | interval,
|  | double | value
| ) |  | const
| virtual

Map a value of a given interval into a color index.

Parameters

  numColors | Number of colors
  interval | Range for all values
  value | Value to map into a color index

Returns
  Index, between 0 and numColors - 1, or -1 for an invalid value

Reimplemented in QwtLinearColorMap.

Definition at line 278 of file qwt_color_map.cpp.

## ◆ colorTable()

QVector< QRgb > QwtColorMap::colorTable | ( | int | numColors | ) | const
| virtual

Build and return a color map of arbitrary number of colors

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

Parameters

  numColors | Number of colors

Returns
  A color table

Definition at line 325 of file qwt_color_map.cpp.

## ◆ colorTable256()

QVector< QRgb > QwtColorMap::colorTable256 | ( |  | ) | 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().

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

Definition at line 304 of file qwt_color_map.cpp.

## ◆ 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 QwtSaturationValueColorMap, QwtHueColorMap, QwtAlphaColorMap, and QwtLinearColorMap.

## ◆ setFormat()

void QwtColorMap::setFormat | ( | Format | format | ) |

Set the format of the color map

Parameters

  format | Format of the color map

Definition at line 264 of file qwt_color_map.cpp.

## Member Data Documentation

## ◆ const

QwtColorMap::Format QwtColorMap::const
| inline

Initial value:
{
return m_format

Returns
  Intended format of the color map

See also
  Format

Definition at line 67 of file qwt_color_map.h.