aqp (version 2.1.0)

colorContrast: Metrics of Contrast Suitable for Comparing Soil Colors

Description

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.

Usage

colorContrast(m1, m2)

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.

Arguments

m1

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

m2

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

Author

D.E. Beaudette

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.

References

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

See Also

colorContrastPlot, huePosition, huePositionCircle

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)

# adjacent chips
colorContrast('10YR 3/3', '10YR 3/4')
colorContrast('10YR 3/3', '7.5YR 3/3')

# 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/')

#
colorContrast(m1 = '10YR 3/3', m2 = 'N 3/')

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)