aqp (version 2.3)

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 = NULL)

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'), must be >1 color if m2 is not specified

m2

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

Author

D.E. Beaudette

Details

This function is fully vectorized over elements of m1 and m2 when both are of the same length. Recycling is not implemented. The minimum set of all pair-wise comparisons are performed within elements of m1 when m2 is not specified. For example, comparisons between A, B, and C are limited to AxB, AxC, and BxC. 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/')

# pair-wise comparisons
m1 <- c('10YR 6/3', '7.5YR 3/3', '10YR 2/2', 'N 3/')
colorContrast(m1)