Metrics of Contrast Suitable for Comparing Soil Colors

Source: R/colorContrast.R

Pair-wise comparisons of Munsell color specifications, based on the NCSS color contrast classes (Soil Survey Technical Note 2) and CIE delta-E 2000 metric.

colorContrast(m1, m2)

Arguments

m1

vector of Munsell colors ('10YR 3/3')

m2

vector of Munsell colors ('10YR 3/6')

Value

data.frame with the following columns:

  • m1: Munsell color 1

  • m2: Munsell color 2

  • dH: delta-hue, as computed by huePosition

  • dV: delta-value, absolute value of difference in Munsell value (m1 vs. m2)

  • dc: delta-chroma, absolute value of difference in Munsell chroma (m1 vs. m2)

  • dE00: delta-E00, e.g. the CIE delta-E as refined in 2000

  • cc: soil color contrast class, as specified in Soil Survey Technical Note 2.

Details

This function is fully vectorized but expects input to be of the same length. Use expand.grid() to generate suitable input from 1:many or many:1 type comparisons. See this tutorial for an expanded discussion and more examples. Neutral colors are not mentioned in SSTN2: in this function any comparison to a neutral color (e.g. 'N 3/') are assigned a delta-hue of 1. Since SSTN2 expects hues to be counted clock wise from 5R, it possible to get very large delta-hue values for otherwise adjacent colors: '5R' vs. '2.5R'. This will be addressed in an update to the standards.

The most meaningful representation of color contrast is the CIE2000 (dE00) metric.

Note

delta-E00 is computed by the farver package.

References

  1. https://en.wikipedia.org/wiki/Color_difference

Author

D.E. Beaudette

Examples


# keep examples from using more than 2 cores
data.table::setDTthreads(Sys.getenv("OMP_THREAD_LIMIT", unset = 2))

# two sets of colors to compare
m1 <- c('10YR 6/3', '7.5YR 3/3', '10YR 2/2', '7.5YR 3/4')
m2 <- c('5YR 3/4', '7.5YR 4/4', '2.5YR 2/2', '7.5YR 6/3')

# contrast metrics
colorContrast(m1, m2)
#>          m1        m2 dH dV dC      dE00        cc
#> 1  10YR 6/3   5YR 3/4  2  3  1 31.286374 Prominent
#> 2 7.5YR 3/3 7.5YR 4/4  0  1  1  9.657423     Faint
#> 3  10YR 2/2 2.5YR 2/2  3  0  0  6.814101     Faint
#> 4 7.5YR 3/4 7.5YR 6/3  0  3  1 30.261643  Distinct

# adjacent chips
colorContrast('10YR 3/3', '10YR 3/4')
#>         m1       m2 dH dV dC     dE00    cc
#> 1 10YR 3/3 10YR 3/4  0  0  1 3.151168 Faint
colorContrast('10YR 3/3', '7.5YR 3/3')
#>         m1        m2 dH dV dC     dE00    cc
#> 1 10YR 3/3 7.5YR 3/3  1  0  0 3.313277 Faint

# highly contrasting colors
# http://colour.granjow.net/fabercastell-polychromos.html
colorContrastPlot('10B 4/13', '10YR 10/15',
labels = c('helioblue-reddish', 'light cadmium yellow')
)



## Note: neutral hues aren't defined in TN2
# approximation / extension of the concept
colorContrast(m1 = 'N 3/', m2 = 'N 6/')
#>     m1   m2 dH dV dC     dE00       cc
#> 1 N 3/ N 6/  0  3  0 17.20472 Distinct

#
colorContrast(m1 = '10YR 3/3', m2 = 'N 3/')
#>         m1   m2 dH dV dC     dE00        cc
#> 1 10YR 3/3 N 3/  1  0  3 22.01338 Prominent

m1 <- c('10YR 6/3', '7.5YR 3/3', '10YR 2/2', 'N 3/')
m2 <- c('5YR 3/4', '7.5YR 4/4', '2.5YR 2/2', '7.5YR 6/3')
colorContrast(m1, m2)
#>          m1        m2 dH dV dC      dE00        cc
#> 1  10YR 6/3   5YR 3/4  2  3  1 31.286374 Prominent
#> 2 7.5YR 3/3 7.5YR 4/4  0  1  1  9.657423     Faint
#> 3  10YR 2/2 2.5YR 2/2  3  0  0  6.814101     Faint
#> 4      N 3/ 7.5YR 6/3  1  3  3 47.668246 Prominent