Package limn.graphics

Record Class Color

java.lang.Object

java.lang.Record

limn.graphics.Color

Record Components:

r - red

g - green

b - blue

a - alpha (1 = opaque)

All Implemented Interfaces:

Paint

public record Color(float r, float g, float b, float a)
extends Record
implements Paint

Immutable straight-alpha RGBA color, channels in [0..1].

Field Summary

Fields

Modifier and Type	Field	Description
static final Color	BLACK
static final Color	TRANSPARENT
static final Color	WHITE

Constructor Summary

Constructors

Constructor	Description
Color(float r, float g, float b, float a)	Creates an instance of a Color record class.

Method Summary

Modifier and Type	Method	Description
float	a()	Returns the value of the a record component.
float	b()	Returns the value of the b record component.
static Color	cmyk(float cyan, float magenta, float yellow, float key, float alpha)	From cyan/magenta/yellow/key, each in [0,1].
static double	contrastRatio(Color a, Color b)	WCAG 2.1 contrast ratio between two colours, from 1 (identical) to 21 (black on white).
final boolean	equals(Object o)	Indicates whether some other object is "equal to" this one.
static Color	fromHex(String text)	Parses #RGB, #RGBA, #RRGGBB or #RRGGBBAA, with or without the #.
float	g()	Returns the value of the g record component.
final int	hashCode()	Returns a hash code value for this object.
static Color	hsv(float hue, float saturation, float value, float alpha)	From hue/saturation/value.
float	hue()	Hue in degrees [0,360).
Color	lerp(Color other, float t)	Linear interpolation between this color and other at t in [0..1].
double	lightness()	CIE L* in [0,100]: perceptual lightness, where a difference of 1 is roughly the smallest step a person can see anywhere on the scale.
float	r()	Returns the value of the r record component.
double	relativeLuminance()	WCAG 2.1 relative luminance in [0,1]: the sRGB channels linearized and weighted for the eye's response, so 0 is black and 1 is white.
static Color	rgb(int rgb)	Opaque color from a 0xRRGGBB value.
static Color	rgba(int rgb, float alpha)	Color from a 0xRRGGBB value plus explicit alpha.
float	saturation()	Saturation in [0,1]: how far from grey.
float[]	toCmyk(float[] out)	Cyan, magenta, yellow and key in [0,1]: the inverse of cmyk(float, float, float, float, float).
String	toHex()	"#RRGGBB", or "#RRGGBBAA" when not fully opaque.
final String	toString()	Returns a string representation of this record class.
float	value()	Value in [0,1]: the brightest channel.
Color	withAlpha(float alpha)

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Details

TRANSPARENT

public static final Color TRANSPARENT

BLACK

public static final Color BLACK

WHITE

public static final Color WHITE

Constructor Details

Color

public Color(float r,
 float g,
 float b,
 float a)

Creates an instance of a Color record class.

Parameters:

r - the value for the r record component

g - the value for the g record component

b - the value for the b record component

a - the value for the a record component

Method Details

rgb

public static Color rgb(int rgb)

Opaque color from a 0xRRGGBB value.

rgba

public static Color rgba(int rgb,
 float alpha)

Color from a 0xRRGGBB value plus explicit alpha.

withAlpha

public Color withAlpha(float alpha)

Returns:

this color with its alpha replaced by alpha

lerp

public Color lerp(Color other,
 float t)

Linear interpolation between this color and other at t in [0..1].

hsv

public static Color hsv(float hue,
 float saturation,
 float value,
 float alpha)

From hue/saturation/value. hue is in degrees and wraps, so 370 and -350 both mean 10; saturation, value and alpha are clamped to [0,1].

hue

public float hue()

Hue in degrees [0,360). Grey has no hue and answers 0; a picker must keep its own hue across a trip through grey, or dragging saturation to zero would lose which colour you were on.

saturation

public float saturation()

Saturation in [0,1]: how far from grey.

value

public float value()

Value in [0,1]: the brightest channel.

cmyk

public static Color cmyk(float cyan,
 float magenta,
 float yellow,
 float key,
 float alpha)

From cyan/magenta/yellow/key, each in [0,1].

Naive, not colour-managed. This is the plain arithmetic conversion every colour picker offers, and it is a convenience for people who think in ink percentages, not a substitute for a profile. Print work needs one; this will not match a press.

toCmyk

public float[] toCmyk(float[] out)

Cyan, magenta, yellow and key in [0,1]: the inverse of cmyk(float, float, float, float, float).

toHex

public String toHex()

"#RRGGBB", or "#RRGGBBAA" when not fully opaque.

fromHex

public static Color fromHex(String text)

Parses #RGB, #RGBA, #RRGGBB or #RRGGBBAA, with or without the #. Missing alpha is opaque.

Returns:

the colour, or null if the text is not one of those forms: a field being typed into is half-written most of the time, and an exception per keystroke is not a parser, it is a nuisance

relativeLuminance

public double relativeLuminance()

WCAG 2.1 relative luminance in [0,1]: the sRGB channels linearized and weighted for the eye's response, so 0 is black and 1 is white.

Alpha is ignored. A translucent colour has no luminance of its own; what a reader sees is the composite. Composite it over its backdrop first (backdrop.lerp(this, this.a())) and ask that colour.

contrastRatio

public static double contrastRatio(Color a,
 Color b)

WCAG 2.1 contrast ratio between two colours, from 1 (identical) to 21 (black on white). Symmetric: which argument is the ink does not change it.

The bars the guideline sets: 4.5 for body text, 3 for large text and for meaningful non-text such as an accent-filled indicator or a focus ring, and 7 for the enhanced (AAA) level.

Both colours must be opaque for the answer to mean anything; see relativeLuminance().

lightness

public double lightness()

CIE L* in [0,100]: perceptual lightness, where a difference of 1 is roughly the smallest step a person can see anywhere on the scale.

This is the scale to measure elevation on. A contrast ratio cannot describe the step from a surface to the card above it in a light palette at all: the step a dark palette reaches at 1.46:1 would need a luminance above 1 to reproduce from a near-white canvas, so the ratio reports two palettes as wildly different when they read identically.

Alpha is ignored, exactly as in relativeLuminance().

toString

public final String toString()

Returns a string representation of this record class. The representation contains the name of the class, followed by the name and value of each of the record components.

Specified by:

toString in class Record

Returns:

a string representation of this object

hashCode

public final int hashCode()

Returns a hash code value for this object. The value is derived from the hash code of each of the record components.

Specified by:

hashCode in class Record

Returns:

a hash code value for this object

equals

public final boolean equals(Object o)

Indicates whether some other object is "equal to" this one. The objects are equal if the other object is of the same class and if all the record components are equal. All components in this record class are compared with '=='.

Specified by:

equals in class Record

Parameters:

o - the object with which to compare

Returns:

true if this object is the same as the o argument; false otherwise.

r

public float r()

Returns the value of the r record component.

Returns:

the value of the r record component

g

public float g()

Returns the value of the g record component.

Returns:

the value of the g record component

b

public float b()

Returns the value of the b record component.

Returns:

the value of the b record component

a

public float a()

Returns the value of the a record component.

Returns:

the value of the a record component