// Specify semi-transparent red
painter.setBrush(QColor(255, 0, 0, 127));
painter.drawRect(0, 0, width()/2, height());

// Specify semi-transparent blue
painter.setBrush(QColor(0, 0, 255, 127));
painter.drawRect(0, 0, width(), height()/2);

Member Function Documentation

QColor::QColor()

Constructs an invalid color with the RGB value (0, 0, 0). An invalid color is a color that is not properly set up for the underlying window system.

The alpha value of an invalid color is unspecified.

See also isValid().

QColor::QColor(int r, int g, int b, int a = 255)

Constructs a color with the RGB value r, g, b, and the alpha-channel (transparency) value of a.

The color is left invalid if any of the arguments are invalid.

See also setRgba() and isValid().

QColor::QColor(QRgb color)

Constructs a color with the value color. The alpha component is ignored and set to solid.

See also fromRgb() and isValid().

QColor::QColor(const QString & name)

Constructs a named color in the same way as setNamedColor() using the given name.

The color is left invalid if the name cannot be parsed.

See also setNamedColor(), name(), and isValid().

QColor::QColor(const char * name)

Constructs a named color in the same way as setNamedColor() using the given name.

The color is left invalid if the name cannot be parsed.

See also setNamedColor(), name(), and isValid().

QColor::QColor(const QColor & color)

Constructs a color that is a copy of color.

See also isValid().

QColor::QColor(Qt::GlobalColor color)

This is an overloaded function.

Constructs a new color with a color value of color.

See also isValid() and Predefined Colors.

[static] bool QColor::allowX11ColorNames()

Returns true if setNamedColor() is allowed to look up colors in the X11 color database. By default, this function returns false.

Note: This function is only available on the X11 platform.

See also setAllowX11ColorNames().

int QColor::alpha() const

Returns the alpha color component of this color.

See also setAlpha(), alphaF(), and Alpha-Blended Drawing.

qreal QColor::alphaF() const

Returns the alpha color component of this color.

See also setAlphaF(), alpha(), and Alpha-Blended Drawing.

int QColor::black() const

Returns the black color component of this color.

See also blackF(), getCmyk(), and The CMYK Color Model.

qreal QColor::blackF() const

Returns the black color component of this color.

See also black(), getCmykF(), and The CMYK Color Model.

int QColor::blue() const

Returns the blue color component of this color.

See also setBlue(), blueF(), and getRgb().

qreal QColor::blueF() const

Returns the blue color component of this color.

See also setBlueF(), blue(), and getRgbF().

[static] QStringList QColor::colorNames()

Returns a QStringList containing the color names Qt knows about.

See also Predefined Colors.

QColor QColor::convertTo(Spec colorSpec) const

Creates a copy of this color in the format specified by colorSpec.

See also spec(), toCmyk(), toHsv(), toRgb(), and isValid().

int QColor::cyan() const

Returns the cyan color component of this color.

See also cyanF(), getCmyk(), and The CMYK Color Model.

qreal QColor::cyanF() const

Returns the cyan color component of this color.

See also cyan(), getCmykF(), and The CMYK Color Model.

QColor QColor::darker(int factor = 200) const

Returns a darker (or lighter) color, but does not change this object.

If the factor is greater than 100, this functions returns a darker color. Setting factor to 300 returns a color that has one-third the brightness. If the factor is less than 100, the return color is lighter, but we recommend using the lighter() function for this purpose. If the factor is 0 or negative, the return value is unspecified.

The function converts the current RGB color to HSV, divides the value (V) component by factor and converts the color back to RGB.

This function was introduced in Qt 4.3.

See also lighter() and isValid().

[static] QColor QColor::fromCmyk(int c, int m, int y, int k, int a = 255)

Static convenience function that returns a QColor constructed from the given CMYK color values: c (cyan), m (magenta), y (yellow), k (black), and a (alpha-channel, i.e. transparency).

All the values must be in the range 0-255.

See also toCmyk(), fromCmykF(), isValid(), and The CMYK Color Model.

[static] QColor QColor::fromCmykF(qreal c, qreal m, qreal y, qreal k, qreal a = 1.0)

This is an overloaded function.

Static convenience function that returns a QColor constructed from the given CMYK color values: c (cyan), m (magenta), y (yellow), k (black), and a (alpha-channel, i.e. transparency).

All the values must be in the range 0.0-1.0.

See also toCmyk(), fromCmyk(), isValid(), and The CMYK Color Model.

[static] QColor QColor::fromHsl(int h, int s, int l, int a = 255)

Static convenience function that returns a QColor constructed from the HSV color values, h (hue), s (saturation), l (lightness), and a (alpha-channel, i.e. transparency).

The value of s, l, and a must all be in the range 0-255; the value of h must be in the range 0-359.

This function was introduced in Qt 4.6.

See also toHsl(), fromHslF(), and isValid().

[static] QColor QColor::fromHslF(qreal h, qreal s, qreal l, qreal a = 1.0)

This is an overloaded function.

Static convenience function that returns a QColor constructed from the HSV color values, h (hue), s (saturation), l (lightness), and a (alpha-channel, i.e. transparency).

All the values must be in the range 0.0-1.0.

This function was introduced in Qt 4.6.

See also toHsl(), fromHsl(), and isValid().

[static] QColor QColor::fromHsv(int h, int s, int v, int a = 255)

Static convenience function that returns a QColor constructed from the HSV color values, h (hue), s (saturation), v (value), and a (alpha-channel, i.e. transparency).

The value of s, v, and a must all be in the range 0-255; the value of h must be in the range 0-359.

See also toHsv(), fromHsvF(), isValid(), and The HSV Color Model.

[static] QColor QColor::fromHsvF(qreal h, qreal s, qreal v, qreal a = 1.0)

This is an overloaded function.

Static convenience function that returns a QColor constructed from the HSV color values, h (hue), s (saturation), v (value), and a (alpha-channel, i.e. transparency).

All the values must be in the range 0.0-1.0.

See also toHsv(), fromHsv(), isValid(), and The HSV Color Model.

[static] QColor QColor::fromRgb(QRgb rgb)

Static convenience function that returns a QColor constructed from the given QRgb value rgb.

The alpha component of rgb is ignored (i.e. it is automatically set to 255), use the fromRgba() function to include the alpha-channel specified by the given QRgb value.

See also fromRgba(), fromRgbF(), toRgb(), and isValid().

[static] QColor QColor::fromRgb(int r, int g, int b, int a = 255)

Static convenience function that returns a QColor constructed from the RGB color values, r (red), g (green), b (blue), and a (alpha-channel, i.e. transparency).

All the values must be in the range 0-255.

See also toRgb(), fromRgbF(), and isValid().

[static] QColor QColor::fromRgbF(qreal r, qreal g, qreal b, qreal a = 1.0)

Static convenience function that returns a QColor constructed from the RGB color values, r (red), g (green), b (blue), and a (alpha-channel, i.e. transparency).

All the values must be in the range 0.0-1.0.

See also fromRgb(), toRgb(), and isValid().

[static] QColor QColor::fromRgba(QRgb rgba)

Static convenience function that returns a QColor constructed from the given QRgb value rgba.

Unlike the fromRgb() function, the alpha-channel specified by the given QRgb value is included.

See also fromRgb() and isValid().

void QColor::getCmyk(int * c, int * m, int * y, int * k, int * a = 0)

Sets the contents pointed to by c, m, y, k, and a, to the cyan, magenta, yellow, black, and alpha-channel (transparency) components of the color's CMYK value.

These components can be retrieved individually using the cyan(), magenta(), yellow(), black() and alpha() functions.

See also setCmyk() and The CMYK Color Model.

void QColor::getCmykF(qreal * c, qreal * m, qreal * y, qreal * k, qreal * a = 0)

Sets the contents pointed to by c, m, y, k, and a, to the cyan, magenta, yellow, black, and alpha-channel (transparency) components of the color's CMYK value.

These components can be retrieved individually using the cyanF(), magentaF(), yellowF(), blackF() and alphaF() functions.

See also setCmykF() and The CMYK Color Model.

void QColor::getHsl(int * h, int * s, int * l, int * a = 0) const

Sets the contents pointed to by h, s, l, and a, to the hue, saturation, lightness, and alpha-channel (transparency) components of the color's HSL value.

These components can be retrieved individually using the hueHsl(), saturationHsl(), lightness() and alpha() functions.

This function was introduced in Qt 4.6.

See also setHsl().

void QColor::getHslF(qreal * h, qreal * s, qreal * l, qreal * a = 0) const

Sets the contents pointed to by h, s, l, and a, to the hue, saturation, lightness, and alpha-channel (transparency) components of the color's HSL value.

These components can be retrieved individually using the hueHslF(), saturationHslF(), lightnessF() and alphaF() functions.

This function was introduced in Qt 4.6.

See also setHsl().

void QColor::getHsv(int * h, int * s, int * v, int * a = 0) const

Sets the contents pointed to by h, s, v, and a, to the hue, saturation, value, and alpha-channel (transparency) components of the color's HSV value.

These components can be retrieved individually using the hue(), saturation(), value() and alpha() functions.

See also setHsv() and The HSV Color Model.

void QColor::getHsvF(qreal * h, qreal * s, qreal * v, qreal * a = 0) const

Sets the contents pointed to by h, s, v, and a, to the hue, saturation, value, and alpha-channel (transparency) components of the color's HSV value.

These components can be retrieved individually using the hueF(), saturationF(), valueF() and alphaF() functions.

See also setHsv() and The HSV Color Model.

void QColor::getRgb(int * r, int * g, int * b, int * a = 0) const

Sets the contents pointed to by r, g, b, and a, to the red, green, blue, and alpha-channel (transparency) components of the color's RGB value.

These components can be retrieved individually using the red(), green(), blue() and alpha() functions.

See also rgb() and setRgb().

void QColor::getRgbF(qreal * r, qreal * g, qreal * b, qreal * a = 0) const

Sets the contents pointed to by r, g, b, and a, to the red, green, blue, and alpha-channel (transparency) components of the color's RGB value.

These components can be retrieved individually using the redF(), greenF(), blueF() and alphaF() functions.

See also rgb() and setRgb().

int QColor::green() const

Returns the green color component of this color.

See also setGreen(), greenF(), and getRgb().

qreal QColor::greenF() const

Returns the green color component of this color.

See also setGreenF(), green(), and getRgbF().

int QColor::hslHue() const

Returns the hue color component of this color.

This function was introduced in Qt 4.6.

See also getHslF() and getHsl().

qreal QColor::hslHueF() const

Returns the hue color component of this color.

This function was introduced in Qt 4.6.

See also hue() and getHslF().

int QColor::hslSaturation() const

Returns the saturation color component of this color.

This function was introduced in Qt 4.6.

See also saturationF(), getHsv(), and The HSV Color Model.

qreal QColor::hslSaturationF() const

Returns the saturation color component of this color.

This function was introduced in Qt 4.6.

See also saturationF() and getHslF().

int QColor::hsvHue() const

Returns the hue color component of this color.

See also hueF(), getHsv(), and The HSV Color Model.

qreal QColor::hsvHueF() const

Returns the hue color component of this color.

See also hue(), getHsvF(), and The HSV Color Model.

int QColor::hsvSaturation() const

Returns the saturation color component of this color.

See also saturationF(), getHsv(), and The HSV Color Model.

qreal QColor::hsvSaturationF() const

Returns the saturation color component of this color.

See also saturation(), getHsvF(), and The HSV Color Model.

int QColor::hue() const

Returns the hue color component of this color.

The color is implicitly converted to HSV.

See also hsvHue(), hueF(), getHsv(), and The HSV Color Model.

qreal QColor::hueF() const

Returns the hue color component of this color.

The color is implicitly converted to HSV.

See also hsvHueF(), hue(), getHsvF(), and The HSV Color Model.

bool QColor::isValid() const

Returns true if the color is valid; otherwise returns false.

[static] bool QColor::isValidColor(const QString & name)

Returns true if the name is a valid color name and can be used to construct a valid QColor object, otherwise returns false.

It uses the same algorithm used in setNamedColor().

This function was introduced in Qt 4.7.

See also setNamedColor().

QColor QColor::lighter(int factor = 150) const

Returns a lighter (or darker) color, but does not change this object.

If the factor is greater than 100, this functions returns a lighter color. Setting factor to 150 returns a color that is 50% brighter. If the factor is less than 100, the return color is darker, but we recommend using the darker() function for this purpose. If the factor is 0 or negative, the return value is unspecified.

The function converts the current RGB color to HSV, multiplies the value (V) component by factor and converts the color back to RGB.

This function was introduced in Qt 4.3.

See also darker() and isValid().

int QColor::lightness() const

Returns the lightness color component of this color.

This function was introduced in Qt 4.6.

See also lightnessF() and getHsl().

qreal QColor::lightnessF() const

Returns the lightness color component of this color.

This function was introduced in Qt 4.6.

See also value() and getHslF().

int QColor::magenta() const

Returns the magenta color component of this color.

See also magentaF(), getCmyk(), and The CMYK Color Model.

qreal QColor::magentaF() const

Returns the magenta color component of this color.

See also magenta(), getCmykF(), and The CMYK Color Model.

QString QColor::name() const

Returns the name of the color in the format "#RRGGBB"; i.e. a "#" character followed by three two-digit hexadecimal numbers.

See also setNamedColor().

int QColor::red() const

Returns the red color component of this color.

See also setRed(), redF(), and getRgb().

qreal QColor::redF() const

Returns the red color component of this color.

See also setRedF(), red(), and getRgbF().

QRgb QColor::rgb() const

Returns the RGB value of the color. The alpha value is opaque.

See also setRgb(), getRgb(), and rgba().

QRgb QColor::rgba() const

Returns the RGB value of the color, including its alpha.

For an invalid color, the alpha value of the returned color is unspecified.

See also setRgba() and rgb().

int QColor::saturation() const

Returns the saturation color component of this color.

The color is implicitly converted to HSV.

See also hsvSaturation(), saturationF(), getHsv(), and The HSV Color Model.

qreal QColor::saturationF() const

Returns the saturation color component of this color.

The color is implicitly converted to HSV.

See also hsvSaturationF(), saturation(), getHsvF(), and The HSV Color Model.

[static] void QColor::setAllowX11ColorNames(bool enabled)

Allow setNamedColor() to look up colors in the X11 color database if enabled. By default, setNamedColor() does not look up colors in the X11 color database.

Note: This function is only available on the X11 platform.

See also setNamedColor() and allowX11ColorNames().

void QColor::setAlpha(int alpha)

Sets the alpha of this color to alpha. Integer alpha is specified in the range 0-255.

See also alpha(), alphaF(), and Alpha-Blended Drawing.

void QColor::setAlphaF(qreal alpha)

Sets the alpha of this color to alpha. qreal alpha is specified in the range 0.0-1.0.

See also alphaF(), alpha(), and Alpha-Blended Drawing.

void QColor::setBlue(int blue)

Sets the blue color component of this color to blue. Integer components are specified in the range 0-255.

See also blue(), blueF(), and setRgb().

void QColor::setBlueF(qreal blue)

Sets the blue color component of this color to blue. Float components are specified in the range 0.0-1.0.

See also blueF(), blue(), and setRgbF().

void QColor::setCmyk(int c, int m, int y, int k, int a = 255)

Sets the color to CMYK values, c (cyan), m (magenta), y (yellow), k (black), and a (alpha-channel, i.e. transparency).

All the values must be in the range 0-255.

See also getCmyk(), setCmykF(), and The CMYK Color Model.

void QColor::setCmykF(qreal c, qreal m, qreal y, qreal k, qreal a = 1.0)

This is an overloaded function.

Sets the color to CMYK values, c (cyan), m (magenta), y (yellow), k (black), and a (alpha-channel, i.e. transparency).

All the values must be in the range 0.0-1.0.

See also getCmykF(), setCmyk(), and The CMYK Color Model.

void QColor::setGreen(int green)

Sets the green color component of this color to green. Integer components are specified in the range 0-255.

See also green(), greenF(), and setRgb().

void QColor::setGreenF(qreal green)

Sets the green color component of this color to green. Float components are specified in the range 0.0-1.0.

See also greenF(), green(), and setRgbF().

void QColor::setHsl(int h, int s, int l, int a = 255)

Sets a HSL color value; h is the hue, s is the saturation, l is the lightness and a is the alpha component of the HSL color.

The saturation, value and alpha-channel values must be in the range 0-255, and the hue value must be greater than -1.

This function was introduced in Qt 4.6.

See also getHsl() and setHslF().

void QColor::setHslF(qreal h, qreal s, qreal l, qreal a = 1.0)

Sets a HSL color lightness; h is the hue, s is the saturation, l is the lightness and a is the alpha component of the HSL color.

All the values must be in the range 0.0-1.0.

This function was introduced in Qt 4.6.

See also getHslF() and setHsl().

void QColor::setHsv(int h, int s, int v, int a = 255)

Sets a HSV color value; h is the hue, s is the saturation, v is the value and a is the alpha component of the HSV color.

The saturation, value and alpha-channel values must be in the range 0-255, and the hue value must be greater than -1.

See also hsv(), getHsv(), setHsvF(), and The HSV Color Model.

void QColor::setHsvF(qreal h, qreal s, qreal v, qreal a = 1.0)

Sets a HSV color value; h is the hue, s is the saturation, v is the value and a is the alpha component of the HSV color.

All the values must be in the range 0.0-1.0.

See also getHsvF(), setHsv(), and The HSV Color Model.

void QColor::setNamedColor(const QString & name)

Sets the RGB value of this QColor to name, which may be in one of these formats:

• #RGB (each of R, G, and B is a single hex digit)
• #RRGGBB
• #RRRGGGBBB
• #RRRRGGGGBBBB
• A name from the list of colors defined in the list of SVG color keyword names provided by the World Wide Web Consortium; for example, "steelblue" or "gainsboro". These color names work on all platforms. Note that these color names are not the same as defined by the Qt::GlobalColor enums, e.g. "green" and Qt::green does not refer to the same color.
• transparent - representing the absence of a color.
• X11 only: If allowX11ColorNames() returns true, any valid X11 color name. See the documentation for XParseColor() for information about valid X11 color names.

The color is invalid if name cannot be parsed.

See also QColor(), name(), isValid(), and allowX11ColorNames().

void QColor::setRed(int red)

Sets the red color component of this color to red. Integer components are specified in the range 0-255.

See also red(), redF(), and setRgb().

void QColor::setRedF(qreal red)

Sets the red color component of this color to red. Float components are specified in the range 0.0-1.0.

See also redF(), red(), and setRgbF().

void QColor::setRgb(int r, int g, int b, int a = 255)

Sets the RGB value to r, g, b and the alpha value to a.

All the values must be in the range 0-255.

See also rgb(), getRgb(), and setRgbF().

void QColor::setRgb(QRgb rgb)

This is an overloaded function.

Sets the RGB value to rgb. The alpha value is set to opaque.

void QColor::setRgbF(qreal r, qreal g, qreal b, qreal a = 1.0)

Sets the color channels of this color to r (red), g (green), b (blue) and a (alpha, transparency).

All values must be in the range 0.0-1.0.

See also rgb(), getRgbF(), and setRgb().

void QColor::setRgba(QRgb rgba)

Sets the RGB value to rgba, including its alpha.

See also rgba() and rgb().

Spec QColor::spec() const

Returns how the color was specified.

See also Spec and convertTo().

QColor QColor::toCmyk() const

Creates and returns a CMYK QColor based on this color.

See also fromCmyk(), convertTo(), isValid(), and The CMYK Color Model.

QColor QColor::toHsl() const

Creates and returns an HSL QColor based on this color.

See also fromHsl(), convertTo(), and isValid().

QColor QColor::toHsv() const

Creates and returns an HSV QColor based on this color.

See also fromHsv(), convertTo(), isValid(), and The HSV Color Model.

QColor QColor::toRgb() const

Create and returns an RGB QColor based on this color.

See also fromRgb(), convertTo(), and isValid().

int QColor::value() const

Returns the value color component of this color.

See also valueF(), getHsv(), and The HSV Color Model.

qreal QColor::valueF() const

Returns the value color component of this color.

See also value(), getHsvF(), and The HSV Color Model.

int QColor::yellow() const

Returns the yellow color component of this color.

See also yellowF(), getCmyk(), and The CMYK Color Model.

qreal QColor::yellowF() const

Returns the yellow color component of this color.

See also yellow(), getCmykF(), and The CMYK Color Model.

QColor::operator QVariant() const

Returns the color as a QVariant

bool QColor::operator!=(const QColor & color) const

Returns true if this color has a different RGB and alpha values from color; otherwise returns false.

QColor & QColor::operator=(const QColor & color)

Assigns a copy of color to this color, and returns a reference to it.

QColor & QColor::operator=(Qt::GlobalColor color)

This is an overloaded function.

Assigns a copy of color and returns a reference to this color.

bool QColor::operator==(const QColor & color) const

Returns true if this color has the same RGB and alpha values as color; otherwise returns false.