DeltaE {spacesXYZ}

Calculate the Color Difference between Two Colors

Description

Calculate Standard CIE Color Differences between two Colors

Usage

DeltaE( Lab1, Lab2, metric=1976 ) 

Arguments

Lab1

a numeric Nx3 matrix with Lab values in the rows, or a vector that can be converted to such a matrix, by row. Lab1 can also be a numeric 3-vector with a single Lab, and it is then replicated to match the size of Lab2.

Lab2

a numeric Nx3 matrix with Lab values in the rows, or a vector that can be converted to such a matrix, by row. Lab2 can also be a numeric 3-vector with a single Lab, and it is then replicated to match the size of Lab1.

metric

a vector of color metric specifiers. Valid values are '1976', '1994', and '2000', which refer to the year the metric was recommended by the CIE. They can also be given as integers, as shown. These metrics are often denoted \Delta E_{1976}, \Delta E_{1994}, and \Delta E_{2000}. When more than one metric is given, a matrix is returned, see Value.

Value

DeltaE() returns a numeric vector of length N, or an NxM matrix. It returns a matrix iff length(metric)= M\ge 2; the column names are set to the metric names. The elements of the output are the pairwise differences, i.e. between row i of Lab1 and row i of Lab2. The names or rownames are set to the rownames of one of the input matrices.

For metric=1976 the distance is simply the Euclidean distance between the two points in Lab, see Hunt p. 111.
For metric=1994 the symmetric variant is used, see Hunt p. 670. There is an asymmetric variant which is not available in this package. The weighting coefficients are for graphic arts (not for textiles).
For metric=2000 the distance is insanely complicated, see Hunt p. 671.
All these metrics are symmetric, which means that swapping Lab1 and Lab2 does not change the result.

References

Hunt, R. W. G. The Reproduction of Colour. 6th Edition. John Wiley & Sons. 2004.

Examples

DeltaE( c(50,0,0),  c(51,2,2,  52,10,11,  46,-13,16)  )
## [1]  3 15 21

path = system.file( "extdata/ciede2000testdata.txt", package='spacesXYZ' )
df   = read.table( path, sep='\t', quote='', head=TRUE )
Lab1 = as.matrix( df[ , 1:3 ] )
Lab2 = as.matrix( df[ , 4:6 ] )
cbind( Lab1, Lab2, DeltaE( Lab1, Lab2, metric=c(1976,2000) ) )[ 1:10, ]

##       LAB_L_REF LAB_A_REF LAB_B_REF LAB_L_SAM LAB_A_SAM LAB_B_SAM DeltaE.1976 DeltaE.2000
##  [1,]   50.0000    2.6772  -79.7751   50.0000    0.0000  -82.7485   4.0010633   2.0424597
##  [2,]   50.0000    3.1571  -77.2803   50.0000    0.0000  -82.7485   6.3141501   2.8615102
##  [3,]   50.0000    2.8361  -74.0200   50.0000    0.0000  -82.7485   9.1776999   3.4411906
##  [4,]   50.0000   -1.3802  -84.2814   50.0000    0.0000  -82.7485   2.0627008   0.9999989
##  [5,]   50.0000   -1.1848  -84.8006   50.0000    0.0000  -82.7485   2.3695707   1.0000047
##  [6,]   50.0000   -0.9009  -85.5211   50.0000    0.0000  -82.7485   2.9152927   1.0000130
##  [7,]   50.0000    0.0000    0.0000   50.0000   -1.0000    2.0000   2.2360680   2.3668588
##  [8,]   50.0000   -1.0000    2.0000   50.0000    0.0000    0.0000   2.2360680   2.3668588
##  [9,]   50.0000    2.4900   -0.0010   50.0000   -2.4900    0.0009   4.9800004   7.1791720
## [10,]   50.0000    2.4900   -0.0010   50.0000   -2.4900    0.0010   4.9800004   7.1791626