---
name: "QwtAlphaColorMap"
section: "3"
platform: "linux"
package: "libqwt-doc"
version: "6.1.4-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/QwtAlphaColorMap"
---

# QwtAlphaColorMap(3)

QwtAlphaColorMap varies the alpha value of a color.

## NAME

QwtAlphaColorMap - **QwtAlphaColorMap** varies the alpha value of a color.

## SYNOPSIS

`#include <qwt_color_map.h>`

Inherits **QwtColorMap**.

### Public Member Functions

**QwtAlphaColorMap** (const QColor &=QColor(Qt::gray))\
 virtual **~QwtAlphaColorMap** ()\
 Destructor.  void **setColor** (const QColor &)\
 QColor **color** () const\
 virtual QRgb **rgb** (const **QwtInterval** &, double value) const\
 Map a value of a given interval into a alpha value.

### Additional Inherited Members

## Detailed Description

**QwtAlphaColorMap** varies the alpha value of a color.

## Constructor & Destructor Documentation

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

Constructor

**Parameters:**

*color* Color of the map

## Member Function Documentation

### QColor QwtAlphaColorMap::color () const

**Returns:**

the color

**See also:**

**setColor()**

### 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()**

## Author

Generated automatically by Doxygen for Qwt User's Guide from the source code.