Defines a color gradient for use with e.g. QCPColorMap. More...

#include <qcustomplot.h>

Public Types
enum	ColorInterpolation { ciRGB, ciHSV }

enum	GradientPreset { gpGrayscale, gpHot, gpCold, gpNight, gpCandy, gpGeography, gpIon, gpThermal, gpPolar, gpSpectrum, gpJet, gpHues }

Public Member Functions
void	clearColorStops ()

QRgb	color (double position, const QCPRange &range, bool logarithmic=false)

ColorInterpolation	colorInterpolation () const

void	colorize (const double data, const QCPRange &range, QRgb scanLine, int n, int dataIndexFactor=1, bool logarithmic=false)

void	colorize (const double data, const unsigned char alpha, const QCPRange &range, QRgb *scanLine, int n, int dataIndexFactor=1, bool logarithmic=false)

QMap< double, QColor >	colorStops () const

QCPColorGradient	inverted () const

int	levelCount () const

void	loadPreset (GradientPreset preset)

bool	operator!= (const QCPColorGradient &other) const

bool	operator== (const QCPColorGradient &other) const

bool	periodic () const

	QCPColorGradient ()

	QCPColorGradient (GradientPreset preset)

void	setColorInterpolation (ColorInterpolation interpolation)

void	setColorStopAt (double position, const QColor &color)

void	setColorStops (const QMap< double, QColor > &colorStops)

void	setLevelCount (int n)

void	setPeriodic (bool enabled)

Protected Member Functions
bool	stopsUseAlpha () const

void	updateColorBuffer ()

Protected Attributes
QVector< QRgb >	mColorBuffer

bool	mColorBufferInvalidated

ColorInterpolation	mColorInterpolation

QMap< double, QColor >	mColorStops

int	mLevelCount

bool	mPeriodic

Detailed Description

Defines a color gradient for use with e.g. QCPColorMap.

This class describes a color gradient which can be used to encode data with color. For example, QCPColorMap and QCPColorScale have setGradient methods which take an instance of this class. Colors are set with setColorStopAt(double position, const QColor &color) with a position from 0 to 1. In between these defined color positions, the color will be interpolated linearly either in RGB or HSV space, see setColorInterpolation.

Alternatively, load one of the preset color gradients shown in the image below, with loadPreset, or by directly specifying the preset in the constructor.

Apart from red, green and blue components, the gradient also interpolates the alpha values of the configured color stops. This allows to display some portions of the data range as transparent in the plot.

The ructor allows directly converting a GradientPreset to a QCPColorGradient. This means that you can directly pass GradientPreset to all the setGradient methods, e.g.:

The total number of levels used in the gradient can be set with setLevelCount. Whether the color gradient shall be applied periodically (wrapping around) to data values that lie outside the data range specified on the plottable instance can be controlled with setPeriodic.

Definition at line 4441 of file qcustomplot.h.

Member Enumeration Documentation

◆ ColorInterpolation

enum QCPColorGradient::ColorInterpolation

Defines the color spaces in which color interpolation between gradient stops can be performed.

See also: setColorInterpolation

Enumerator
ciRGB	Color channels red, green and blue are linearly interpolated.
ciHSV	Color channels hue, saturation and value are linearly interpolated (The hue is interpolated over the shortest angle distance)

Definition at line 4450 of file qcustomplot.h.

◆ GradientPreset

enum QCPColorGradient::GradientPreset

Defines the available presets that can be loaded with loadPreset. See the documentation there for an image of the presets.

Enumerator
gpGrayscale	Continuous lightness from black to white (suited for non-biased data representation)
gpHot	Continuous lightness from black over firey colors to white (suited for non-biased data representation)
gpCold	Continuous lightness from black over icey colors to white (suited for non-biased data representation)
gpNight	Continuous lightness from black over weak blueish colors to white (suited for non-biased data representation)
gpCandy	Blue over pink to white.
gpGeography	Colors suitable to represent different elevations on geographical maps.
gpIon	Half hue spectrum from black over purple to blue and finally green (creates banding illusion but allows more precise magnitude estimates)
gpThermal	Colors suitable for thermal imaging, ranging from dark blue over purple to orange, yellow and white.
gpPolar	Colors suitable to emphasize polarity around the center, with blue for negative, black in the middle and red for positive values.
gpSpectrum	An approximation of the visible light spectrum (creates banding illusion but allows more precise magnitude estimates)
gpJet	Hue variation similar to a spectrum, often used in numerical visualization (creates banding illusion but allows more precise magnitude estimates)
gpHues	Full hue cycle, with highest and lowest color red (suitable for periodic data, such as angles and phases, see setPeriodic)

Definition at line 4459 of file qcustomplot.h.

Constructor & Destructor Documentation

◆ QCPColorGradient() [1/2]

QCPColorGradient::QCPColorGradient ( )

Constructs a new, empty QCPColorGradient with no predefined color stops. You can add own color stops with setColorStopAt.

The color level count is initialized to 350.

Definition at line 15790 of file qcustomplot.cpp.

◆ QCPColorGradient() [2/2]

QCPColorGradient::QCPColorGradient ( GradientPreset preset )

Constructs a new QCPColorGradient initialized with the colors and color interpolation according to preset.

The color level count is initialized to 350.

Definition at line 15805 of file qcustomplot.cpp.

Member Function Documentation

◆ clearColorStops()

void QCPColorGradient::clearColorStops ( )

Clears all color stops.

See also: setColorStops, setColorStopAt

Definition at line 16257 of file qcustomplot.cpp.

◆ color()

QRgb QCPColorGradient::color	(	double	position,
		const QCPRange &	range,
		bool	logarithmic = `false`
	)

Definition at line 16116 of file qcustomplot.cpp.

◆ colorInterpolation()

ColorInterpolation QCPColorGradient::colorInterpolation ( ) const

inline

Definition at line 4482 of file qcustomplot.h.

◆ colorize() [1/2]

void QCPColorGradient::colorize	(	const double *	data,
		const QCPRange &	range,
		QRgb *	scanLine,
		int	n,
		int	dataIndexFactor = `1`,
		bool	logarithmic = `false`
	)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

This method is used to quickly convert a data array to colors. The colors will be output in the array scanLine. Both data and scanLine must have the length n when passed to this function. The data range that shall be used for mapping the data value to the gradient is passed in range. logarithmic indicates whether the data values shall be mapped to colors logarithmically.

if data actually contains 2D-data linearized via [row*columnCount + column], you can set dataIndexFactor to columnCount to convert a column instead of a row of the data array, in scanLine. scanLine will remain a regular (1D) array. This works because data is addressed data[i*dataIndexFactor].

Use the overloaded method to additionally provide alpha map data.

The QRgb values that are placed in scanLine have their r, g and b components premultiplied with alpha (see QImage::Format_ARGB32_Premultiplied).

Definition at line 15927 of file qcustomplot.cpp.

◆ colorize() [2/2]

void QCPColorGradient::colorize	(	const double *	data,
		const unsigned char *	alpha,
		const QCPRange &	range,
		QRgb *	scanLine,
		int	n,
		int	dataIndexFactor = `1`,
		bool	logarithmic = `false`
	)

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Additionally to the other overload of colorize, this method takes the array alpha, which has the same size and structure as data and encodes the alpha information per data point.

The QRgb values that are placed in scanLine have their r, g and b components premultiplied with alpha (see QImage::Format_ARGB32_Premultiplied).

Definition at line 16001 of file qcustomplot.cpp.

◆ colorStops()

QMap<double, QColor> QCPColorGradient::colorStops ( ) const

inline

Definition at line 4481 of file qcustomplot.h.

◆ inverted()

QCPColorGradient QCPColorGradient::inverted ( ) const

Returns an inverted gradient. The inverted gradient has all properties as this QCPColorGradient, but the order of the color stops is inverted.

See also: setColorStops, setColorStopAt

Definition at line 16269 of file qcustomplot.cpp.

◆ levelCount()

int QCPColorGradient::levelCount ( ) const

inline

Definition at line 4480 of file qcustomplot.h.

◆ loadPreset()

void QCPColorGradient::loadPreset ( GradientPreset preset )

Clears the current color stops and loads the specified preset. A preset consists of predefined color stops and the corresponding color interpolation method.

The available presets are:

Definition at line 16148 of file qcustomplot.cpp.

◆ operator!=()

bool QCPColorGradient::operator!= ( const QCPColorGradient & other ) const

inline

Definition at line 4477 of file qcustomplot.h.

◆ operator==()

bool QCPColorGradient::operator== ( const QCPColorGradient & other ) const

Definition at line 15816 of file qcustomplot.cpp.

◆ periodic()

bool QCPColorGradient::periodic ( ) const

inline

Definition at line 4483 of file qcustomplot.h.

◆ setColorInterpolation()

void QCPColorGradient::setColorInterpolation ( QCPColorGradient::ColorInterpolation interpolation )

Sets whether the colors in between the configured color stops (see setColorStopAt) shall be interpolated linearly in RGB or in HSV color space.

For example, a sweep in RGB space from red to green will have a muddy brown intermediate color, whereas in HSV space the intermediate color is yellow.

Definition at line 15880 of file qcustomplot.cpp.

◆ setColorStopAt()

void QCPColorGradient::setColorStopAt	(	double	position,
		const QColor &	color
	)

Sets the color the gradient will have at the specified position (from 0 to 1). In between these color stops, the color is interpolated according to setColorInterpolation.

See also: setColorStops, clearColorStops

Definition at line 15867 of file qcustomplot.cpp.

◆ setColorStops()

void QCPColorGradient::setColorStops ( const QMap< double, QColor > & colorStops )

Sets at which positions from 0 to 1 which color shall occur. The positions are the keys, the colors are the values of the passed QMap colorStops. In between these color stops, the color is interpolated according to setColorInterpolation.

A more convenient way to create a custom gradient may be to clear all color stops with clearColorStops (or creating a new, empty QCPColorGradient) and then adding them one by one with setColorStopAt.

See also: clearColorStops

Definition at line 15855 of file qcustomplot.cpp.

◆ setLevelCount()

void QCPColorGradient::setLevelCount ( int n )

Sets the number of discretization levels of the color gradient to n. The default is 350 which is typically enough to create a smooth appearance. The minimum number of levels is 2.

Definition at line 15830 of file qcustomplot.cpp.

◆ setPeriodic()

void QCPColorGradient::setPeriodic ( bool enabled )

Sets whether data points that are outside the configured data range (e.g. QCPColorMap::setDataRange) are colored by periodically repeating the color gradient or whether they all have the same color, corresponding to the respective gradient boundary color.

As shown in the image above, gradients that have the same start and end color are especially suitable for a periodic gradient mapping, since they produce smooth color transitions throughout the color map. A preset that has this property is gpHues.

In practice, using periodic color gradients makes sense when the data corresponds to a periodic dimension, such as an angle or a phase. If this is not the case, the color encoding might become ambiguous, because multiple different data values are shown as the same color.

Definition at line 15904 of file qcustomplot.cpp.

◆ stopsUseAlpha()

bool QCPColorGradient::stopsUseAlpha ( ) const

protected

Definition at line 16283 of file qcustomplot.cpp.

◆ updateColorBuffer()

void QCPColorGradient::updateColorBuffer ( )

protected

Definition at line 16298 of file qcustomplot.cpp.

Member Data Documentation

◆ mColorBuffer

QVector<QRgb> QCPColorGradient::mColorBuffer

protected

Definition at line 4508 of file qcustomplot.h.

◆ mColorBufferInvalidated

bool QCPColorGradient::mColorBufferInvalidated

protected

Definition at line 4509 of file qcustomplot.h.

◆ mColorInterpolation

ColorInterpolation QCPColorGradient::mColorInterpolation

protected

Definition at line 4504 of file qcustomplot.h.

◆ mColorStops

QMap<double, QColor> QCPColorGradient::mColorStops

protected

Definition at line 4503 of file qcustomplot.h.

◆ mLevelCount

int QCPColorGradient::mLevelCount

protected

Definition at line 4502 of file qcustomplot.h.

◆ mPeriodic

bool QCPColorGradient::mPeriodic

protected

Definition at line 4505 of file qcustomplot.h.

The documentation for this class was generated from the following files:

Public Types

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

◆ ColorInterpolation

◆ GradientPreset

Constructor & Destructor Documentation

◆ QCPColorGradient() [1/2]

◆ QCPColorGradient() [2/2]

Member Function Documentation

◆ clearColorStops()

◆ color()

◆ colorInterpolation()

◆ colorize() [1/2]

◆ colorize() [2/2]

◆ colorStops()

◆ inverted()

◆ levelCount()

◆ loadPreset()

◆ operator!=()

◆ operator==()

◆ periodic()

◆ setColorInterpolation()

◆ setColorStopAt()

◆ setColorStops()

◆ setLevelCount()

◆ setPeriodic()

◆ stopsUseAlpha()

◆ updateColorBuffer()

Member Data Documentation

◆ mColorBuffer

◆ mColorBufferInvalidated

◆ mColorInterpolation

◆ mColorStops

◆ mLevelCount

◆ mPeriodic