Table of Contents

Class ColorUtils

Namespace
NixUniversalSDK
Assembly
NixUniversalSDK.dll

Color math utility functions

public static class ColorUtils
Inheritance
ColorUtils
Inherited Members

Methods

AdaptXyz(double[], double[], double[])

Adapts colour in XYZ from one reference white to another using Bradford adaptation method. NOTE: refIn, refOut, xyzIn must all be on the same scale

public static double[] AdaptXyz(double[] xyzIn, double[] refIn, double[] refOut)

Parameters

xyzIn double[]

Source color, referenced to refIn (element order X, Y, Z)

refIn double[]

Source reference white (element order X, Y, Z)

refOut double[]

Destination reference white (element order X, Y, Z)

Returns

double[]

Adapted color, referenced to refOut (element order X, Y, Z)

ClipXyz(double[], double[])

Clips CIEXYZ values in between 0 and the value of the reference white to ensure X, Y, Z are in the proper range.

public static double[] ClipXyz(double[] xyz, double[] xyzRef)

Parameters

xyz double[]

CIEXYZ value (element order X, Y, Z)

xyzRef double[]

CIEXYZ value for reference white (X, Y, Z)

Returns

double[]

Clipped CIEXYZ value (element order X, Y, Z)

CmykToXyz(double[], double[], bool)

Calculates XYZ value from CMYK input using built-in lookup tables

public static double[] CmykToXyz(double[] cmykIn, double[] refOut, bool bpc)

Parameters

cmykIn double[]

CMYK colour input, unity scale (element order C, M, Y, K)

refOut double[]

Reference white value for XYZ output, unity scale (element order X, Y, Z)

bpc bool

Set to true to perform black point compensation

Returns

double[]

XYZ value output, unity scale (element order X, Y, Z)

CmykToXyz(double[], double[], bool, double[][], int[][], int[][], int[][])

Calculates XYZ value from CMYK input using lookup tables provided as input arguments

public static double[] CmykToXyz(double[] cmykIn, double[] refOut, bool bpc, double[][] m, int[][] input, int[][] clut, int[][] output)

Parameters

cmykIn double[]

CMYK colour input, unity scale (element order C, M, Y, K)

refOut double[]

Reference white value for XYZ output, unity scale (element order X, Y, Z)

bpc bool

Set to true to perform black point compensation

m double[][]

3x3 Extracted from ICC profile: transformation matrix to perform on LAB value (NOT used in current function)

input int[][]

256x4 Extracted from ICC profile: InputCurves

clut int[][]

6561x3 Extracted from ICC profile: CMYK to LAB LUT (flattened 9x9x9x9 array with 3 channels, one each for L, A, B)

output int[][]

Extracted from ICC profile: OutputCurves (NOT used in current function, default profile has 1:1 output)

Returns

double[]

XYZ value output, unity scale (element order X, Y, Z)

DegToRad(double)

Converts angle in degrees to radians (used in dE2000 function)

public static double DegToRad(double deg)

Parameters

deg double

Angle in degrees

Returns

double

Angle in radians

DeltaE00(double[], double[], double, double, double)

Takes two CIELAB values and calculates color difference (dE) using the CIE2000 formula. NOTE: both CIELAB values must share the same reference white. If they do not, convert to XYZ, adapt, convert back to CIELAB before calculating dE.

public static double DeltaE00(double[] lab1, double[] lab2, double kL = 1, double kC = 1, double kH = 1)

Parameters

lab1 double[]

First CIELAB value (element order L, a, b)

lab2 double[]

Second CIELAB value (element order L, a, b)

kL double

Model parameter (optional, default 1)

kC double

Model parameter (optional, default 1)

kH double

Model parameter (optional, default 1)

Returns

double

Delta E (2000) value

DeltaE76(double[], double[])

Takes two CIELAB values and calculates color difference (dE) using CIE1976 formula. NOTE: both CIELAB values must share the same reference white. If they do not: convert to XYZ, adapt, convert back to CIELAB before calculating dE.

public static double DeltaE76(double[] lab1, double[] lab2)

Parameters

lab1 double[]

First CIELAB value (element order L, a, b)

lab2 double[]

Second CIELAB value (element order L, a, b)

Returns

double

Delta E (1976) value

DeltaE94(double[], double[], double, double, double)

Takes two CIELAB values and calculates color difference (dE) using the CIE1994 formula. Requires weighting factors kL, k1, and k2 which are dependent on application. Use DeltaE94G(double[], double[]) for graphic design applications andDeltaE94T(double[], double[]) for textile applications. Both CIELAB values must share the same reference white.If they do not, convert to XYZ, adapt, convert back to CIELAB before calculating dE.

public static double DeltaE94(double[] lab1, double[] lab2, double kL, double k1, double k2)

Parameters

lab1 double[]

First CIELAB value (element order L, a, b)

lab2 double[]

Second CIELAB value (element order L, a, b)

kL double

Weighting factor (application dependent)

k1 double

Weighting factor (application dependent)

k2 double

Weighting factor (application dependent)

Returns

double

Delta E (1994) value

DeltaE94G(double[], double[])

Takes two CIELAB values and calculates color difference (dE) using the CIE1994 formula for the graphic design application (kL = 1, k1 = 0.045, k2 = 0.015). See also DeltaE94(double[], double[], double, double, double)

public static double DeltaE94G(double[] lab1, double[] lab2)

Parameters

lab1 double[]

First CIELAB value (element order L, a, b)

lab2 double[]

Second CIELAB value (element order L, a, b)

Returns

double

Delta E (1994) value

DeltaE94T(double[], double[])

Takes two CIELAB values and calculates color difference (dE) using the CIE1994 formula for the textiles design application (kL = 2, k1 = 0.048, k2 = 0.014). See also DeltaE94(double[], double[], double, double, double)

public static double DeltaE94T(double[] lab1, double[] lab2)

Parameters

lab1 double[]

First CIELAB value (element order L, a, b)

lab2 double[]

Second CIELAB value (element order L, a, b)

Returns

double

Delta E (1994) value

DeltaECmc(double[], double[], double, double)

Takes two CIELAB values and calculates color difference (dE) using the CMC(l:c) formula. Depends on model parameters l and c; common values used are CMC(2:1) for acceptability and CMC(1:1) for perceptibility.

public static double DeltaECmc(double[] lab1, double[] lab2, double l, double c)

Parameters

lab1 double[]

First CIELAB value (element order L, a, b)

lab2 double[]

First CIELAB value (element order L, a, b)

l double

Model parameter l

c double

Model parameter c

Returns

double

Delta E (CMC) value

LabToLch(double[])

Takes CIELAB value and converts to polar coordinates (LCH)

public static double[] LabToLch(double[] labIn)

Parameters

labIn double[]

CIELAB value (element order L, a, b)

Returns

double[]

LCHab value (element order L, c, h). Hue angle h is in degrees

LabToXyz(double[], Illuminant, Observer)

Takes CIELAB value and its reference white to calculate CIEXYZ value

public static double[] LabToXyz(double[] lab, Illuminant illuminant, Observer observer)

Parameters

lab double[]
illuminant Illuminant

Illuminant for reference white point

observer Observer

Observer for reference white point

Returns

double[]

CIEXYZ value (element order X, Y, Z)

LabToXyz(double[], ReferenceWhite)

Takes CIELAB value and its reference white to calculate CIEXYZ value

public static double[] LabToXyz(double[] lab, ReferenceWhite reference)

Parameters

lab double[]

CIELAB value (element order L, a, b)

reference ReferenceWhite

Reference white point for input CIEXYZ value

Returns

double[]

CIEXYZ value (element order X, Y, Z)

LabToXyz(double[], double[])

Takes CIELAB value and its reference white to calculate CIEXYZ value

public static double[] LabToXyz(double[] lab, double[] xyzRef)

Parameters

lab double[]

CIELAB value (element order L, a, b)

xyzRef double[]

Reference white (element order X, Y, Z)

Returns

double[]

CIEXYZ value (element order X, Y, Z)

LchToLab(double[])

Takes LCHab value and converts to CIELAB

public static double[] LchToLab(double[] lchIn)

Parameters

lchIn double[]

LCHab value (element order L, c, h). Hue angle h is in degrees

Returns

double[]

CIELAB value (element order L, a, b)

LchToLuv(double[])

Takes LCHuv value and converts to CIELUV

public static double[] LchToLuv(double[] lchIn)

Parameters

lchIn double[]

LCHuv value (element order L, c, h). Hue angle h is in degrees

Returns

double[]

CIELUV value (element order L, u, v)

LuvToLch(double[])

Takes CIELUV value and converts to polar coordinates (LCH)

public static double[] LuvToLch(double[] LuvIn)

Parameters

LuvIn double[]

CIELUV value (element order L, u, v)

Returns

double[]

LCHuv value (element order L, c, h). Hue angle h is in degrees

LuvToXyz(double[], double[])

Takes CIELUV value and its reference white to calculate CIEXYZ value

public static double[] LuvToXyz(double[] luvIn, double[] xyzRef)

Parameters

luvIn double[]

CIELUV value (element order L, u, v)

xyzRef double[]

CIEXYZ reference white (element order X, Y, Z)

Returns

double[]

CIEXYZ value (element order X, Y, Z)

RadToDeg(double)

Converts angle in radians to degrees (used in dE2000 function)

public static double RadToDeg(double rads)

Parameters

rads double

Angle in radians

Returns

double

Angle in degrees

RgbToXyz(double[], double[], double[], double[], double[], double[])

Calculates XYZ from linear RGB given chromaticity coordinates of RGB working space primaries and reference whites of RGB and XYZ value.

public static double[] RgbToXyz(double[] rgbIn, double[] rC, double[] gC, double[] bC, double[] wC, double[] refOut)

Parameters

rgbIn double[]

Input linear RGB value, unity scale (element order R, G, B)

rC double[]

RGB space red primary chromaticity coordinates (element order x, y)

gC double[]

RGB space green primary chromaticity coordinates (element order x, y)

bC double[]

RGB space blue primary chromaticity coordinates (element order x, y)

wC double[]

RGB space reference white/grey chromaticity coordinates (element order x, y)

refOut double[]

Selected reference white of output XYZ color, unity scale (element order X, Y, Z)

Returns

double[]

XYZ value, unity scale, with reference white refOut (element order X, Y, Z)

RgbTripletToHexString(byte[])

Takes a RGB triplet and formats it as a HEX string (e.g. - "#RRGGBB")

public static string RgbTripletToHexString(byte[] rgb)

Parameters

rgb byte[]

Returns

string

Exceptions

ArgumentException

Thrown if array does not have three entries

SRgbToXyz(byte[], double[])

Calculates XYZ from sRGB value

public static double[] SRgbToXyz(byte[] sRgb, double[] refOut)

Parameters

sRgb byte[]

Non-linear sRGB value, 0 - 255 scale (element order R, G, B)

refOut double[]

Reference white of colour output, unity scale (element order X, Y, Z)

Returns

double[]

XYZ value, unity scale, with reference white refOut (element order X, Y, Z)

Spectral10ToDensity(int[], float[], DensityStatus)

Takes reflectance data on 10 nm intervals and calculates CMYK densities according to ISO 5-3:2009. Data must be provided on 10 nm intervals corresponding to the nearest 10 nanometer. Density values are calculated across the range 340 - 770 nm. If the provided data spans a shorter range (e.g. - 400 - 700 nm), the values at the boundaries are repeated.

public static double[] Spectral10ToDensity(int[] lambda, float[] reflectance, DensityStatus status)

Parameters

lambda int[]

Wavelength values of provided reflectance data.

reflectance float[]

Reflectance data. Must contain the same number of elements as lambda

status DensityStatus

Selected density status

Returns

double[]

CMYK densities (element order C, M, Y, K)

Spectral10ToXyz(int[], float[], Illuminant, Observer)

Takes reflectance data on 10 nm intervals and calculates a CIEXYZ value according to ASTM E308. Data must be provided on 10 nm intervals corresponding to the nearest 10 nanometer. CIEXYZ values are calculated across the range 360 - 780 nm.If the provided data spans a shorter range (e.g. - 400 - 700 nm), the values at the boundaries are repeated.

public static double[] Spectral10ToXyz(int[] lambda, float[] reflectance, Illuminant illuminant, Observer observer)

Parameters

lambda int[]

Wavelength values of provided reflectance data.

reflectance float[]

Reflectance data. Must contain the same number of elements as lambda

illuminant Illuminant

Reference illuminant

observer Observer

Reference observer

Returns

double[]

CIEXYZ value reported on 0 - 1.0 scale (element order X, Y, Z)

Spectral10ToXyz(int[], float[], ReferenceWhite)

Takes reflectance data on 10 nm intervals and calculates a CIEXYZ value according to ASTM E308. Data must be provided on 10 nm intervals corresponding to the nearest 10 nanometer. CIEXYZ values are calculated across the range 360 - 780 nm. If the provided data spans a shorter range (e.g. - 400 - 700 nm), the values at the boundaries are repeated.

public static double[] Spectral10ToXyz(int[] lambda, float[] reflectance, ReferenceWhite reference)

Parameters

lambda int[]

Wavelength values of provided reflectance data.

reflectance float[]

Reflectance data. Must contain the same number of elements as lambda

reference ReferenceWhite

Selected reference white

Returns

double[]

CIEXYZ value reported on 0 - 1.0 scale (element order X, Y, Z)

XyzChromaticity(double[])

Calculates chromaticity coordinates x,y from a given xyz value. WARNING: Be aware that for black xyz(0, 0, 0), the result is undefined. For this case, use chromaticity of reference white instead.

public static double[] XyzChromaticity(double[] xyz)

Parameters

xyz double[]

Source color (element order X, Y, Z)

Returns

double[]

Chromaticity of input color, unity scale (element order x, y)

XyzToCmyk(double[], double[], bool)

Calculates CMYK value from XYZ input using built in lookup tables

public static double[] XyzToCmyk(double[] xyzIn, double[] xyzRef, bool bpc)

Parameters

xyzIn double[]

XYZ colour, unity scale (element order X, Y, Z)

xyzRef double[]

Reference white value for xyzIn, unity scale (element order X, Y, Z)

bpc bool

Black point compensation enabled / disabled

Returns

double[]

CMYK value on unity scale (element order C, M, Y, K)

XyzToCmyk(double[], double[], bool, double[][], int[][], int[][], int[][])

Calculates CMYK value from XYZ using lookup tables provided as inputCurves arguments

public static double[] XyzToCmyk(double[] xyzIn, double[] xyzRef, bool bpc, double[][] m, int[][] inputCurves, int[][] clut, int[][] outputCurves)

Parameters

xyzIn double[]

XYZ colour, unity scale (element order X, Y, Z)

xyzRef double[]

Reference white value for xyzIn, unity scale (element order X, Y, Z)

bpc bool

Black point compensation enabled / disabled

m double[][]

3x3 Extracted from ICC profile: transformation matrix to perform on LAB value (code only tested with identity matrix)

inputCurves int[][]

256x3 Extracted from ICC profile: InputCurves

clut int[][]

35937x4: Extracted from ICC profile: Lab to CMYK LUT (flattened 33x33x33 array with 4 channels, one each for C,M,Y,K)

outputCurves int[][]

256x4: Extracted from ICC profile: OutputCurves

Returns

double[]

CMYK value on unity scale (element order C, M, Y, K)

XyzToLab(double[], Illuminant, Observer)

Takes CIEXYZ value and its reference white to calculate CIELAB value. Value xyz and xyzRef must be either unity (Y on 0 - 1) input.

public static double[] XyzToLab(double[] xyz, Illuminant illuminant, Observer observer)

Parameters

xyz double[]
illuminant Illuminant

Illuminant for reference white point

observer Observer

Observer for reference white point

Returns

double[]

CIELAB value (element order L, a, b)

XyzToLab(double[], ReferenceWhite)

Takes CIEXYZ value and its reference white to calculate CIELAB value. Value xyz and xyzRef must be either unity (Y on 0 - 1) input.

public static double[] XyzToLab(double[] xyz, ReferenceWhite reference)

Parameters

xyz double[]

CIEXYZ value (element order X, Y, Z)

reference ReferenceWhite

Reference white point for input CIEXYZ value

Returns

double[]

CIELAB value (element order L, a, b)

XyzToLab(double[], double[])

Takes CIEXYZ value and its reference white to calculate CIELAB value. Values xyz and xyzRef can be either unity (0 - 1) or scaled (0 - 100) input, but both vectors must be the same scale. (i.e., if xyz is unity scale, xyzRef must also be unity scale)

public static double[] XyzToLab(double[] xyz, double[] xyzRef)

Parameters

xyz double[]

CIEXYZ value (element order X, Y, Z)

xyzRef double[]

CIEXYZ value for reference white (X, Y, Z)

Returns

double[]

CIELAB value (element order L, a, b)

XyzToLuv(double[], double[])

Takes CIEXYZ value and its reference white to calculate CIELUV value.

public static double[] XyzToLuv(double[] xyzIn, double[] xyzRef)

Parameters

xyzIn double[]

CIEXYZ value (element order X, Y, Z)

xyzRef double[]

CIEXYZ reference white (element order X, Y, Z)

Returns

double[]

CIELUV value (element order L, u, v)

XyzToRgb(double[], double[], double[], double[], double[], double[])

Calculates linear RGB from XYZ given chromaticity coordinates of RGB working space primaries and reference whites of RGB and XYZ value

public static double[] XyzToRgb(double[] xyzIn, double[] refIn, double[] rC, double[] gC, double[] bC, double[] wC)

Parameters

xyzIn double[]

Input colour XYZ values, unity scale (element order X, Y, Z)

refIn double[]

Reference white of input colour xyzIn, unity scale (element order X, Y, Z)

rC double[]

RGB space red primary chromaticity coordinates (element order x, y)

gC double[]

RGB space green primary chromaticity coordinates (element order x, y)

bC double[]

RGB space blue primary chromaticity coordinates (element order x, y)

wC double[]

RGB space reference white/grey chromaticity coordinates (element order x, y)

Returns

double[]

XyzToSRgb(double[], double[])

Calculates companded sRGB value from XYZ given reference white of XYZ value.

public static byte[] XyzToSRgb(double[] xyzIn, double[] refIn)

Parameters

xyzIn double[]

Input colour XYZ values, unity scale (element order X, Y, Z)

refIn double[]

Reference white of input colour xyzIn, unity scale (element order X, Y, Z)

Returns

byte[]

Non-linear sRGB value, 0 - 255 scale (element order R, G, B)