# QwtAlphaColorMap Class Reference

QwtAlphaColorMap variies the alpha value of a color. More...

`#include <qwt_color_map.h>`

Inheritance diagram for QwtAlphaColorMap:
[legend]

List of all members.

## Public Types

enum | Format { RGB, Indexed }

## Public Member Functions

QColor | color () const
QColor | color (const QwtInterval &, double value) const
virtual QVector< QRgb > | colorTable (const QwtInterval &) const
Format | format () const
| QwtAlphaColorMap (const QColor &=QColor(Qt::gray))
virtual QRgb | rgb (const QwtInterval &, double value) const
void | setColor (const QColor &)
virtual | ~QwtAlphaColorMap ()

## Detailed Description

QwtAlphaColorMap variies the alpha value of a color.

## Member Enumeration Documentation

enum QwtColorMap::Format`[inherited]`

Format for color mapping

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

Enumerator:

  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.

## Constructor & Destructor Documentation

QwtAlphaColorMap::QwtAlphaColorMap | ( | const QColor & | color = `QColor( Qt::gray )` | ) |

Constructor

Parameters:

  color | Color of the map

QwtAlphaColorMap::~QwtAlphaColorMap | ( |  | ) | `[virtual]`

Destructor.

## Member Function Documentation

QColor QwtAlphaColorMap::color | ( |  | ) | const

Returns:
  the color

See also:
  setColor()

QColor QwtColorMap::color | ( | const QwtInterval & | interval,
|  | double | value
| ) |  | const`[inline, inherited]`

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().

QVector< QRgb > QwtColorMap::colorTable | ( | const QwtInterval & | interval | ) | const`[virtual, inherited]`

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

QwtColorMap::Format QwtColorMap::format | ( |  | ) | const`[inline, inherited]`

Returns:
  Intended format of the color map

See also:
  Format

QRgb QwtAlphaColorMap::rgb | ( | const QwtInterval & | interval,
|  | double | value
| ) |  | const`[virtual]`

Map a value of a given interval into a alpha value.

alpha := (value - interval.minValue()) / interval.width();

Parameters:

  interval | Range for all values
  value | Value to map into a rgb value

Returns:
  rgb value, with an alpha value

Implements QwtColorMap.

void QwtAlphaColorMap::setColor | ( | const QColor & | color | ) |

Set the color

Parameters:

  color | Color

See also:
  color()