Vespucci  1.0.0
Public Types | Public Member Functions | Protected Member Functions | Protected Attributes | List of all members
QCPColorGradient Class Reference

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,
  cbBuGn, cbBuPu, cbGnBu, cbOrRd,
  cbPuBu, cbPuBuGn, cbPuRd, cbRdPu,
  cbYlGn, cbYlGnBu, cbYlOrBr, cbYlOrRd,
  cbBlues, cbGreens, cbGreys, cbOranges,
  cbPurples, cbReds, cbBrBG, cbPiYG,
  cbPRGn, cbPuOr, cbRdBu, cbRdGy,
  cbRdYlBu, cbRdYlGn, cbSpectral, cbCluster9,
  cbCluster8, cbCluster7, cbCluster6, cbCluster5,
  cbCluster4, cbCluster3, cbCluster2, vSpectral
}
 

Public Member Functions

 QCPColorGradient (GradientPreset preset=gpCold)
 
bool operator== (const QCPColorGradient &other) const
 
bool operator!= (const QCPColorGradient &other) const
 
int levelCount () const
 
QMap< double, QColor > colorStops () const
 
ColorInterpolation colorInterpolation () const
 
bool periodic () const
 
void setLevelCount (int n)
 
void setColorStops (const QMap< double, QColor > &colorStops)
 
void setColorStopAt (double position, const QColor &color)
 
void setColorInterpolation (ColorInterpolation interpolation)
 
void setPeriodic (bool enabled)
 
void colorize (const double *data, const QCPRange &range, QRgb *scanLine, int n, int dataIndexFactor=1, bool logarithmic=false)
 
QRgb color (double position, const QCPRange &range, bool logarithmic=false)
 
void loadPreset (GradientPreset preset)
 
void clearColorStops ()
 
QCPColorGradient inverted () const
 

Protected Member Functions

void updateColorBuffer ()
 

Protected Attributes

int mLevelCount
 
QMap< double, QColor > mColorStops
 
ColorInterpolation mColorInterpolation
 
bool mPeriodic
 
QVector< QRgb > mColorBuffer
 
bool mColorBufferInvalidated
 

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.

QCPColorGradient.png

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

colorMap->setGradient(QCPColorGradient::gpHot);

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 1905 of file qcustomplot.h.

Member Enumeration Documentation

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 1914 of file qcustomplot.h.

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)

cbBuGn 
cbBuPu 
cbGnBu 
cbOrRd 
cbPuBu 
cbPuBuGn 
cbPuRd 
cbRdPu 
cbYlGn 
cbYlGnBu 
cbYlOrBr 
cbYlOrRd 
cbBlues 
cbGreens 
cbGreys 
cbOranges 
cbPurples 
cbReds 
cbBrBG 
cbPiYG 
cbPRGn 
cbPuOr 
cbRdBu 
cbRdGy 
cbRdYlBu 
cbRdYlGn 
cbSpectral 
cbCluster9 
cbCluster8 
cbCluster7 
cbCluster6 
cbCluster5 
cbCluster4 
cbCluster3 
cbCluster2 
vSpectral 

Definition at line 1923 of file qcustomplot.h.

Constructor & Destructor Documentation

QCPColorGradient::QCPColorGradient ( GradientPreset  preset = gpCold)

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 11196 of file qcustomplot.cpp.

Member Function Documentation

void QCPColorGradient::clearColorStops ( )

Clears all color stops.

See also
setColorStops, setColorStopAt

Definition at line 12014 of file qcustomplot.cpp.

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

Definition at line 11386 of file qcustomplot.cpp.

ColorInterpolation QCPColorGradient::colorInterpolation ( ) const
inline

Definition at line 1990 of file qcustomplot.h.

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

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].

Definition at line 11311 of file qcustomplot.cpp.

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

Definition at line 1989 of file qcustomplot.h.

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 12026 of file qcustomplot.cpp.

int QCPColorGradient::levelCount ( ) const
inline

Definition at line 1988 of file qcustomplot.h.

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:

QCPColorGradient.png

Definition at line 11418 of file qcustomplot.cpp.

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

Definition at line 1985 of file qcustomplot.h.

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

Definition at line 11207 of file qcustomplot.cpp.

bool QCPColorGradient::periodic ( ) const
inline

Definition at line 1991 of file qcustomplot.h.

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 11270 of file qcustomplot.cpp.

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 11257 of file qcustomplot.cpp.

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 and then adding them one by one with setColorStopAt.

See also
clearColorStops

Definition at line 11245 of file qcustomplot.cpp.

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.

QCPColorGradient-levelcount.png

Definition at line 11221 of file qcustomplot.cpp.

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.

QCPColorGradient-periodic.png

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 11294 of file qcustomplot.cpp.

void QCPColorGradient::updateColorBuffer ( )
protected

Definition at line 12040 of file qcustomplot.cpp.

Member Data Documentation

QVector<QRgb> QCPColorGradient::mColorBuffer
protected

Definition at line 2017 of file qcustomplot.h.

bool QCPColorGradient::mColorBufferInvalidated
protected

Definition at line 2018 of file qcustomplot.h.

ColorInterpolation QCPColorGradient::mColorInterpolation
protected

Definition at line 2013 of file qcustomplot.h.

QMap<double, QColor> QCPColorGradient::mColorStops
protected

Definition at line 2012 of file qcustomplot.h.

int QCPColorGradient::mLevelCount
protected

Definition at line 2011 of file qcustomplot.h.

bool QCPColorGradient::mPeriodic
protected

Definition at line 2014 of file qcustomplot.h.

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