Centroid Notations for the Revised ISCC-NBS Color-Name Blocks

Description

CentroidsISCCNBS is a table with the centroids of the revised ISCC-NBS Color-Name Blocks, taken from Kelly (1958)

Format

This data.frame has 267 rows and these columns:

Number

ISCC-NBS number (an integer from 1 to 267)

Name

ISCC-NBS name

MunsellSpec

Munsell specification of the centroid of the block a (character string)

Details

The earliest paper I am aware of is by Nickerson, et. al. in 1941. After the big Munsell renotation in 1943, the name blocks were revised in 1955.
When the central colors were recomputed in Kelly (1958), they were called the "Central Colors", though the text makes it clear that most are truly centroids, which were computed from the centroid of an "elementary shape", which is a "sector of a right cylindrical annulus". For the "peripheral blocks" of high chroma, the centroids were "estimated graphically by plotting the MacAdam limits".
In Kelly (1965) these were called "centroid colors", and that is the name we will use here.

Contributor

Glenn Davis

References

Nickerson, Dorothy and Sidney M. Newhall. Central Notations for ISCC-NBS Color names. J Opt. Soc. Am. Vol 31 Iss. 9. pp. 597-591. 1941.

Newhall, Sidney M., Dorothy Nickerson, Deane B. Judd. Final Report of the O.S.A. Subcommitte on the Spacing of the Munsell Colors. Journal of the Optical Society of America. Vol. 33. No. 7. pp. 385-418. July 1943.

Kelly, Kenneth L. and Deane B. Judd The ISCC-NBS Method of Designating Colors and a Dictionary of Color Names. National Bureau of Standards Circular 553. Washington DC: US Government Printing Office. November 1, 1955.

Kelly, Kenneth Low. Central Notations for the Revised ISCC-NBS Color-Name Blocks. Journal of Research of the National Bureau of Standards. Research Paper 2911. Vol. 61 No. 5. pp. 427-431. November 1958.

Kelly, Kenneth Low. A Universal Color Language. Color Engineering. Vol. 3 No. 2. pp. 2-7. March-April, 1965.

Examples

print( CentroidsISCCNBS[ 1:5, ] )

##    Number          Name   MunsellSpec
##  1      1    vivid pink     1.5R 7/13
##  2      2   strong pink  1.5R 7.5/9.1
##  3      3     deep pink 1.9R 6.0/11.1
##  4      4    light pink  2.5R 8.6/5.2
##  5      5 moderate pink  2.5R 7.2/5.2

Get ISCC-NBS Number and ISCC-NBS Name from Munsell HVC or Munsell Notation

Description

Get ISCC-NBS Number and ISCC-NBS Name from Munsell HVC or Munsell Notation.

Usage

ColorBlockFromMunsell( MunsellSpec ) 

Arguments

Details

The ISCC-NBS System is a partition of Munsell Color Solid into 267 color blocks. Each block is a disjoint union of elementary blocks, where an elementary block is defined by its minimum and maximum limits in Hue, Value, and Chroma. Some blocks are non-convex. The peripheral blocks, of which there are 120, have arbitrary large chroma and are considered semi-infinite for this function; there is no consideration of the MacAdam limits. For each query vector HVC, the function searches a private data.frame with 932 elementary blocks, for the one elementary block that contains it.

Value

a data.frame with N rows and these columns:

The rownames are set to the input MunsellSpec.

History

The Munsell Book of Color was published in 1929. The first ISCC-NBS partition, in 1939, had 319 blocks and names (including 5 neutrals). There were no block numbers. The aimpoints of the Munsell samples were thoroughly revised in 1943. The ISCC-NBS partition was revised in 1955, and this is the version used here.

Future Work

It might be useful to compute the distance from the query point to the boundary of the containing color block.

Author(s)

Glenn Davis

References

Munsell Color Company, A.H. Munsell, and A.E.O. Munsell. Munsell book of color: defining, explaining, and illustrating the fundamental characteristics of color. 1929.

Judd, Deane B. and Kenneth L. Kelly. Method of Designating Colors. Journal of Research of the National Bureau of Standards. Research Paper 1239. Volume 23 Issue 3. pp. 355-385. September 1939.

Newhall, Sidney M., Dorothy Nickerson, Deane B. Judd. Final Report of the O.S.A. Subcommitte on the Spacing of the Munsell Colors. Journal of the Optical Society of America. Vol. 33. No. 7. pp. 385-418. July 1943.

Kelly, Kenneth L. and Deane B. Judd The ISCC-NBS Method of Designating Colors and a Dictionary of Color Names. National Bureau of Standards Circular 553. Washington DC: US Government Printing Office. November 1, 1955.

See Also

CentroidsISCCNBS

Examples

ColorBlockFromMunsell( c( "3R 8/3", "7.4YR 3/4" ) )

##            HVC.H HVC.V HVC.C Number           Name      Centroid
##  3R 8/3      3.0   8.0   3.0      4     light pink  2.5R 8.6/5.2
##  7.4YR 3/4  17.4   3.0   4.0     58 moderate brown 5.5YR 3.5/3.9

Convert Colorlab Munsell Format to Munsell HVC

Description

Convert Colorlab Munsell Format to Munsell HVC

Usage

ColorlabFormatToMunsellSpec( HVCH )

Arguments

Details

Colorlab Munsell format uses 4 numbers.

1. Hue Step, in the interval (0,10], or 0 for neutrals

2. Munsell Value, in the interval (0,10]

3. Munsell Chroma, non-negative

4. Hue Index, an integer from 1 to 10, or 0 for neutrals

Value

an Nx3 matrix, with each row an HVC vector. Value and Chroma are simply copied unchanged. The complex part is conversion of Colorlab Hue Step and Hue Index to Hue Number. For neutrals, both Hue Step and Hue Index are ignored. Invalid input values, such as a Hue Index that is not an integer from 0 to 10 (except for neutrals), are converted to NAs. The rownames of the input are copied to the output, but if these are NULL, the rownames are set to the Munsell notations.

Author(s)

Jose Gama and Glenn Davis

References

Color Processing Toolbox. Colorlab 1.0. https://www.uv.es/vista/vistavalencia/software/colorlab.html

See Also

MunsellSpecToColorlabFormat()

Examples

ColorlabFormatToMunsellSpec( c( 3.2,3,2,1,  2,5.1,0,0, 2,5.1,0.1,0 ) )
##                     H   V  C
##  3.20B 3.00/2.00 63.2 3.0  2
##  N 5.10/          0.0 5.1  0
##  <NA>              NA  NA NA

Convert Munsell Notation to numerical Munsell HVC

Description

Convert Munsell Notation to numerical Munsell HVC

Usage

HVCfromMunsellName( MunsellName )
MunsellHVC( MunsellName )
HueNumberFromString( HueString )

Arguments

Value

HVCfromMunsellName() returns a numeric Nx3 matrix with HVC in the rows. For neutral colors, both H and C are set to 0. If a string cannot be parsed, the entire row is set to NAs. The rownames are set to MunsellName.
MunsellHVC() returns a character Nx3 matrix with HVC in the rows, and is there for backward compatibility with older versions of the package. For neutral colors, H is set to 'N' and C is set to '0'.
HueNumberFromString() returns the hue number H (in (0,100]). If the string cannot be parsed, or the color is neutral, the output is set to NA.
For all functions the Hue Number is wrapped to (0,100].

Note

Ever since the Munsell Book of Color (1929), the Munsell hue circle has been divided into 5 principal hues and 5 intermediate hues, to define a total of 10 arcs. Each of these hues has been assigned a 10-point scale, with 5 at the midpoint of the arc. Moreover, the hue "origin" has been at '10RP'. So a 100-point scale (with no letters) for the entire hue circle is obvious and trivial to construct, but I have been unable to determine the first explicit mention of such a scale. The earliest I have have found is from Nimeroff (1968), Figures 20 and 21 on page 27.

There is a reference to ASTM D 1535 in the References of Nimeroff, but it is not dated, and the 2 figures are not attributed to it. There was an ASTM D 1535 in 1968 but I have not been able to locate it; it is possible that the 100-point scale first appeared in ASTM D-1535 (1968), or even earlier in ASTM D 1525-58T (1958).
Interestingly, in the Atlas of the Munsell Color System (1915) there were only 5 principal hues (with no intermediate hues) and each of the 5 arcs was assigned a 10-point scale. If the entire hue circle of 1915 were assigned a scale, it would have been a 50-point scale.

Author(s)

Glenn Davis

References

Nimeroff, I. Colorimetry. National Bureau of Standards Monograph 104. January 1968. 35 cents.

ASTM D 1535-80. Standard Practice for Specifying Color by the Munsell System. 1980.

Munsell Book of Color: defining, explaining, and illustrating the fundamental characteristics of color. Munsell Color Co. 1929.

Atlas of the Munsell Color System. Malden, Mass., Wadsworth, Howland & Co., inc., Printers. 1915.

See Also

MunsellNameFromHVC(), HueStringFromNumber()

Examples

HVCfromMunsellName( c( "4.2P 2.9/3.8", "N 2.3/", "N 8.9/0" ) )
##                  H   V   C
##  4.2P 2.9/3.8 84.2 2.9 3.8
##  N 2.3/        0.0 2.3 0.0
##  N 8.9/0       0.0 8.9 0.0

HueNumberFromString( c('4B','4.6GY','10RP','N') )
##  [1]  64.0  34.6 100.0    NA

Test xyY Coordinates for being Inside the MacAdam Limits

Description

Test xyY Coordinates for being Inside the MacAdam Limits for Illuminants C and D65

Usage

IsWithinMacAdamLimits( xyY, Illuminant='C' )

Arguments

Details

The MacAdam Limit is the boundary of the optimal color solid (also called the Rösch Farbkörper), in XYZ coordinates. The optimal color solid is convex and depends on the illuminant. Points on the boundary of the solid are called optimal colors. It is symmetric about the midpoint of the segment joining black and white (the 50% gray point). It can be expressed as a zonohedron - a convex polyhedron with a special form; for details on zonohedra, see Centore.

For each of the 2 illuminants, a zonohedron Z is pre-computed (and stored in sysdata.rda). The wavelengths used are 380 to 780 nm with 5nm step (81 wavelengths). Each zonohedron has 81*80=6480 parallelogram faces, though some of them are coplanar. Z is expressed as the intersection of 6480 halfspaces. The plane equation of each parallelogram is pre-computed, but redundant ones are not removed (in this version).

For testing a query point xyY, a pseudo-distance metric \delta is used. Let the zonohedron Z be the intersection of the halfspaces ⟨ h_i,x ⟩ \le b_i ~~ i=1,...,n, where each h_i is a unit vector. The point xyY is converted to XYZ, and \delta(XYZ) is computed as: \delta(XYZ) := max( ⟨ h_i,XYZ ⟩ - b_i ) where the maximum is taken over all i=1,...,n. This calculation can be optimized; because the zonohedron is centrally symmetric, only half of the planes actually have to be stored, and this cuts the memory and processing time in half. It is clear that XYZ is within the zonohedron iff \delta(XYZ) \le 0, and that XYZ is on the boundary iff \delta(XYZ)=0. This pseudo-distance is part of the returned data.frame.

An interesting fact is that if \delta(XYZ)>0, then \delta(XYZ) \le dist(XYZ,Z), with equality iff the segment from XYZ to the point z on the boundary of Z closest to XYZ is normal to one of the faces of Z that contains z. This is why we call \delta a pseudo-distance. Another interesting fact is that if \delta(XYZ) \le 0, then \delta(XYZ) = -min( \Psi_Z(u) - ⟨ u,XYZ ⟩ ), where the minimum is taken over all unit vectors u and where \Psi_Z is the support function of Z.

Value

A data.frame with N rows and these columns:

The row names of the output value are set equal to the row names of xyY.

Author(s)

Glenn Davis and Jose Gama

References

Centore, Paul. A zonohedral approach to optimal colours. Color Research & Application. Vol. 38. No. 2. pp. 110-119. April 2013.

Rösch, S. Darstellung der Farbenlehre für die Zwecke des Mineralogen. Fortschr. Mineral. Krist. Petrogr. Vol. 13 No. 143. 1929.

MacAdam, David L. Maximum Visual Efficiency of Colored Materials. Journal of the Optical Society of America. Vol 25, No. 11. pp. 361-367. November 1935.

Wikipedia. Support Function. https://en.wikipedia.org/wiki/Support_function

Examples

IsWithinMacAdamLimits( c(0.6,0.3,10, 0.6,0.3,20, 0.6,0.3,30, 0.6,0.3,40  ), 'C' )

##    within  delta
##  1   TRUE -1.941841
##  2   TRUE -1.332442
##  3  FALSE  3.513491
##  4  FALSE 12.826172

Convert CIE Lab coordinates to Munsell HVC

Description

LabToMunsell Converts CIE Lab coordinates to Munsell HVC, by interpolating over the extrapolated Munsell renotation data

Usage

LabToMunsell( Lab, white='D65', adapt='Bradford', ... )

Arguments

Details

The conversion is done in these steps.

• Lab → XYZ using spacesXYZ::XYZfromLab() with the given white.

• XYZ is then adapted from the given white to Illuminant C using the given adapt method.

• XYZ → HVC using XYZtoMunsell().

Value

An Nx3 matrix with the Munsell HVC coordinates in each row. The rownames are set to those of Lab.

Note

The case of the letter 't' in the function name was recently changed from lower to upper. The function LabtoMunsell() is equivalent but deprecated and provided for a limited time.

Author(s)

Jose Gama and Glenn Davis

References

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

MunsellToLab(), XYZtoMunsell(), spacesXYZ::standardXYZ(), spacesXYZ::CAT(), spacesXYZ::XYZfromLab()

Examples

LabToMunsell( c(74.613450, -20.4, 10.1,    80, 0, 0) )
##                      H        V       C
##  3.1G 7.4/3.6 43.13641 7.379685 3.62976
##  N 7.9/        0.00000 7.945314 0.00000

Convert CIE Luv coordinates to Munsell HVC

Description

LuvToMunsell Converts CIE Luv coordinates to Munsell HVC, by interpolating over the extrapolated Munsell renotation data

Usage

LuvToMunsell( Luv, white='D65', adapt='Bradford', ... ) 

Arguments

Details

The conversion is done in these steps:

• Luv → XYZ using spacesXYZ::XYZfromLuv() with the given white.

• XYZ is then adapted from the given white to Illuminant C using the given chromatic adaptation method, see spacesXYZ::CAT().

• XYZ → HVC using XYZtoMunsell()

Value

An Nx3 matrix with the Munsell HVC coordinates in each row. The rownames are set to those of Luv.

Note

The case of the letter 't' in the function name was recently changed from lower to upper. The function LuvtoMunsell() is equivalent but deprecated and provided for a limited time.

Author(s)

Jose Gama and Glenn Davis

References

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

XYZtoMunsell(), spacesXYZ::XYZfromLuv(), spacesXYZ::standardXYZ(), spacesXYZ::CAT()

Examples

LuvToMunsell( c( 74.613450, -5.3108, 10.6,  55, 0, 0 ) )
##                      H        V        C
##  8.7GY 7.4/1.2 38.6599 7.383948 1.229376
##  N 5.4/         0.0000 5.395003 0.000000

The Munsell HVC to xy 3D Lookup Table

Description

This is the discrete data for the Munsell Renotation System, which is often considered to be the most perceptually uniform color atlas. It was created by the NBS and OSA from "3,000,000 color judgments" by 40 observers.

Format

A data frame with 4995 observations of the following 6 variables.

• H the Munsell Hue. Each H is a multiple of 2.5 and in the interval (0,100].

• V the Munsell Value. Each V is an integer from 1 to 10, or one of 0.2, 0.4, 0.6, 0.8

• C the Munsell Chroma. Each C is a positive even integer.

• x the x chromaticity coordinate, for Illuminant C.

• y the y chromaticity coordinate, for Illuminant C.

• real a logical value. If TRUE then x,y were published, otherwise they have been extrapolated.

Note that the luminance factor Y is *not* here, since Y is a simple function of V, see YfromV().

Details

All the (x,y) data here comes from the file all.dat downloaded from Rochester Institute of Technology, see Source. The file real.dat is a subset, and contains the (x,y) published in Newhall, et. al. (1943). These rows have real=TRUE and are only for Value \ge 1. There are 2734 of these.
Similarly, for Value<1 (very dark colors), (x,y) data from the paper Judd et. al. (1956) also have real=TRUE. There are 355 of these.
So all.dat has 4995 colors, of which 2734+355=3089 are "real" colors, and the remaining 1906 are extrapolated. I am confident that the extrapolation was done by Schleter et. al. (1958) at the NBS, and put online by the Rochester Institute of Technology. For more details, and the abstract of the 1958 article, see the munsellinterpol User Guide.

Note

For the purpose of this package, I have found that the extrapolated (x,y) for V\ge1 work well. But for V<1 they did not work so well, and I was able to get better results with my own extrapolation. Moreover, to get reliable results in this package for high Chroma, it was necessary to extrapolate past the data in all.dat.

Author(s)

Glenn Davis

Source

Rochester Institute of Technology. Program of Color Science. Munsell Renotation Data. https://www.rit.edu/science/munsell-color-lab

References

Newhall, Sidney M., Dorothy Nickerson, Deane B. Judd. Final Report of the O.S.A. Subcommitte on the Spacing of the Munsell Colors. Journal of the Optical Society of America. Vol. 33. No. 7. pp. 385-418. July 1943.

Judd, Deane B. and Gunter Wyszecki. Extension of the Munsell Renotation System to Very Dark Colors. Journal of the Optical Society of America. Vol. 46. No. 4. pp. 281-284. April 1956.

Schleter, J. C, D. B. Judd, D. B., H. J. Keegan. Extension of the Munsell Renotation System (Abstract). J. Opt. Soc. Am. Vol 48. Num. 11. pp. 863-864. presented at the Forty-Third Annual Meeting of the Optical Society of America. Statler Hilton Hotel, Detroit, Michigan. October 9, 10, and 11, 1958.

See Also

YfromV()

Examples

str(Munsell2xy)

##  'data.frame':	4995 obs. of  6 variables:
##   $ H   : num  32.5 35 37.5 37.5 40 40 42.5 42.5 45 45 ...
##   $ V   : num  0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 ...
##   $ C   : num  2 2 2 4 2 4 2 4 2 4 ...
##   $ x   : num  0.713 0.449 0.262 -0.078 0.185 -0.257 0.144 -0.235 0.117 -0.209 ...
##   $ y   : num  1.414 1.145 0.837 2.16 0.676 ...
##   $ real: logi  FALSE FALSE FALSE FALSE TRUE FALSE ...

Convert Munsell Numeric to Munsell String Notation

Description

Convert Munsell Numeric to Munsell String Notation

Usage

MunsellNameFromHVC( HVC, format='g', digits=2 )

HueStringFromNumber( Hue, format='g', digits=2 )

Arguments

Value

Both functions return a character vector of length N. MunsellNameFromHVC() returns the full notation. HueStringFromNumber() returns just initial the hue part; which is useful for labeling plots.

Note

If format='f', then Chroma is first rounded to to the given digits. Chromas close to 0 may then become 0 and be displayed as a neutral, see Examples.
The width argument of formatC() is always set to 1, to suppress leading spaces.

Author(s)

Glenn Davis

References

ASTM D 1535-97. Standard Practice for Specifying Color by the Munsell System. 1997

See Also

formatC(), HVCfromMunsellName(), HueNumberFromString()

Examples

MunsellNameFromHVC( c(39,5.1,7.3,  0,5.1234,0.003 )  )
##  [1] "9GY 5.1/7.3"    "10RP 5.1/0.003"

MunsellNameFromHVC( c(39,5.1,7.34,  0,5.1234,0.003 ), format='f' )
##  [1] "9.00GY 5.10/7.34" "N 5.10/"

HueStringFromNumber( seq( 2.5, 100, by=2.5 ) )   # make nice labels for a plot
##   [1] "2.5R"  "5R"    "7.5R"  "10R"   "2.5YR" "5YR"   "7.5YR" "10YR"  "2.5Y" 
##  [10] "5Y"    "7.5Y"  "10Y"   "2.5GY" "5GY"   "7.5GY" "10GY"  "2.5G"  "5G"   
##  [19] "7.5G"  "10G"   "2.5BG" "5BG"   "7.5BG" "10BG"  "2.5B"  "5B"    "7.5B" 
##  [28] "10B"   "2.5PB" "5PB"   "7.5PB" "10PB"  "2.5P"  "5P"    "7.5P"  "10P"  
##  [37] "2.5RP" "5RP"   "7.5RP" "10RP" 

Convert Munsell Specification to Colorlab Format

Description

Convert Munsell Specification to Colorlab Format

Usage

MunsellSpecToColorlabFormat( MunsellSpec )

Arguments

Details

Colorlab Munsell format uses 4 numbers.

1. Hue Step, in the interval (0,10], or 0 for neutrals. In Colorlab documentation it is called the hue shade. It is also the Hue Number H mod 10 (unless H is an exact multiple of 10).

2. Munsell Value, in the interval [0,10]

3. Munsell Chroma, non-negative

4. Hue Index, an integer from 1 to 10, or 0 for neutrals. This index defines the principal hue, see Details.

Value

an Nx4 matrix, with rows as described in Details. Value and Chroma are simply copied unchanged. The complex part is conversion of Hue Number to Colorlab Hue Step and Hue Index. If Chroma is 0, both the Hue Step and Hue Index are set to 0. Invalid input values are converted to NAs.
If the input is a character vector, the rownames of the returned matrix are set to that vector.

Note

The Colorlab format is closer to the Munsell Book of Color (1929) than HVC. In the book the hue circle is divided into 10 principal hues - 5 simple and 5 compound. The 10 hue labels are: R, YR, Y, GY G, BG, B, PB, P (simple are 1 letter and compound are 2 letters). In Colorlab these labels are replaced by the Hue Index. WARNING: In the Munsell System, see Cleland, there is a different Hue Index - R is 1, YR is 2, ..., P is 10. The Colorlab index has a different origin, and goes around the circle in a different direction !
Each one of these major hues corresponds to an arc on the circle, with a 10-point hue scale. The midpoint of the arc has hue step = 5. Fortunately this 10-point hue scale is exactly the same as the Colorlab Hue Step.

Author(s)

Jose Gama and Glenn Davis

References

Color Processing Toolbox. Colorlab 1.0. https://www.uv.es/vista/vistavalencia/software/colorlab.html

Cleland, T. M. A Practical description of the Munsell Color System with Suggestions for its Use. (1921)

See Also

HVCfromMunsellName(), ColorlabFormatToMunsellSpec()

Examples

MunsellSpecToColorlabFormat( c(100,5,5, 10,3,4, 90,4,3, 77,1,2, 66,2,0, 0,1,2 ) )
##                    HN V C HI
##  10.00RP 5.00/5.00 10 5 5  8
##  10.00R 3.00/4.00  10 3 4  7
##  10.00P 4.00/3.00  10 4 3  9
##  7.00PB 1.00/2.00   7 1 2 10
##  N 2.00/            0 2 0  0
##  10.00RP 1.00/2.00 10 1 2  8

Convert a Munsell specification to CIE Lab coordinates

Description

MunsellToLab Converts a Munsell specification to CIE Lab coordinates, by interpolating over the extrapolated Munsell renotation data

Usage

MunsellToLab( MunsellSpec, white='D65', adapt='Bradford', ... ) 

Arguments

Details

The conversion is done in these steps:

• HVC → XYZ using MunsellToXYZ()

• XYZ is adapted from Illuminant C to the given white using spacesXYZ::adaptXYZ() and the given chromatic adaptation method

• XYZ → Lab using spacesXYZ::LabfromXYZ() with the given white

Value

An Nx3 matrix with the Lab coordinates in each row. The rownames of Lab are copied from the input HVC matrix, unless the rownames are NULL and then the output rownames are the Munsell notations for HVC.

Author(s)

Jose Gama and Glenn Davis

References

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

LabToMunsell(), MunsellToXYZ(), spacesXYZ::LabfromXYZ(), spacesXYZ::standardXYZ(), spacesXYZ::adaptXYZ(), spacesXYZ::CAT()

Examples

MunsellToLab( c('7.6P 8.9/2.2', 'N 5/' ) )
##                      L       a         b
##  7.6P 8.9/2.2 89.19097 5.09879 -3.250468
##  N 5/         51.00375 0.00000  0.000000

Convert a Munsell specification to CIE Luv coordinates

Description

MunsellToLuv Converts a Munsell specification to CIE Luv coordinates, by interpolating over the extrapolated Munsell renotation data

Usage

MunsellToLuv( MunsellSpec, white='D65', adapt='Bradford', ... ) 

Arguments

Details

The conversion is done in these steps:

• HVC → XYZ using MunsellToXYZ()

• XYZ is adapted from Illuminant C to the given white using spacesXYZ::adaptXYZ() with the given chromatic adaptation method

• XYZ → Luv using spacesXYZ::LuvfromXYZ() with the given white

Value

An Nx3 matrix with the Luv coordinates in each row. The rownames of Luv are copied from the input HVC matrix, unless the rownames are NULL and then the output rownames are the Munsell notations for HVC.

Author(s)

Jose Gama and Glenn Davis

References

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

LuvToMunsell(), MunsellToXYZ(), spacesXYZ::standardXYZ(), spacesXYZ::CAT(), spacesXYZ::adaptXYZ(), spacesXYZ::LuvfromXYZ()

Examples

MunsellToLuv( c('7.6P 8.9/2.2', 'N 5/' ) )
##                      L        u         v
##  7.6P 8.9/2.2 89.19097 5.247155 -5.903808
##  N 5/         51.00375 0.000000  0.000000

Convert a Munsell specification to RGB coordinates

Description

MunsellToRGB Converts a Munsell specification to RGB coordinates, by interpolating over the extrapolated Munsell renotation data

Usage

MunsellToRGB( MunsellSpec, space='sRGB', which='scene', maxSignal=255, 
    adapt='Bradford', ... ) 

Arguments

Details

The conversion is done with these steps:

• HVC → xyY using MunsellToxyY() with .... This xyY is for Illuminant C.

• xyY → XYZ using spacesXYZ::XYZfromxyY()

• XYZ is adapted from Illuminant C to the white-point (with which) of the RGB space, using spacesXYZ::adaptXYZ(), with the given chromatic adaptation method adapt

• XYZ → RGB using spacesRGB::RGBfromXYZ() with the given space, which, and maxSignal

Value

a data.frame with these columns:

In case of error, it returns NULL.

Author(s)

Jose Gama and Glenn Davis

References

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

MunsellToXYZ(), IsWithinMacAdamLimits(), spacesRGB::installRGB(), spacesRGB::RGBfromXYZ(), spacesXYZ::XYZfromxyY(), spacesXYZ::CAT()

Examples

MunsellToRGB( c('7.6P 8.9/2.2', 'N 3/'), space='AdobeRGB' )
##     SAMPLE_NAME      xyY.x      xyY.y      xyY.Y     RGB.R     RGB.G     RGB.B OutOfGamut
##  1 7.6P 8.9/2.2  0.3109520  0.3068719 74.6134498 227.72419 220.18659 229.23297      FALSE
##  2         N 3/  0.3101000  0.3163000  6.3911778  73.01793  73.01793  73.01793      FALSE

Convert a Munsell specification to CIE XYZ coordinates

Description

MunsellToXYZ Converts a Munsell specification to XYZ coordinates, by interpolating over the extrapolated Munsell renotation data

Usage

MunsellToXYZ( MunsellSpec, ... ) 

Arguments

Details

The conversion is done in these steps:

• HVC → xyY using MunsellToxyY() and .... This xyY is for Illuminant C.

• xyY → XYZ using spacesXYZ::XYZfromxyY()

Value

an Nx3 matrix with XYZ values in the rows. The rownames of XYZ are copied from the input HVC matrix, unless the rownames are NULL and then the output rownames are the Munsell notations for HVC. Note that these XYZ values are for viewing under Illuminant C, with Y=100. There is no chromatic adaptation.

Author(s)

Jose Gama and Glenn Davis

References

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

MunsellToxyY(), spacesXYZ::XYZfromxyY()

Examples

MunsellToXYZ('7.6P 8.9/2.2')
##                     X        Y        Z
##  7.6P 8.9/2.2 75.6055 74.61345 92.92308

Convert a Munsell specification to sRGB coordinates

Description

MunsellTosRGB Converts a Munsell specification to non-linear sRGB coordinates, by interpolating over the extrapolated Munsell renotation data

Usage

MunsellTosRGB( MunsellSpec, maxSignal=255, ... ) 

Arguments

Details

The conversion is done in these steps.

• HVC → xyY using MunsellToxyY() and the given .... This xyY is for Illuminant C.

• xyY → XYZ using spacesXYZ::XYZfromxyY()

• XYZ is adapted from Illuminant C to Illuminant D65 (from the sRGB standard) using spacesXYZ::adaptXYZ() and the Bradford chromatic adaptation method

• XYZ → sRGB using spacesRGB::RGBfromXYZ() with the given maxSignal

Value

a data.frame with these columns:

Note

The more general function MunsellToRGB() also performs this conversion. The main reason to use MunsellTosRGB() is that it takes a little less time, since the CAT (using the Bradford method) is precomputed during base::.onLoad().

Author(s)

Jose Gama and Glenn Davis

References

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

MunsellToXYZ(), MunsellToRGB(), spacesXYZ::XYZfromxyY(), spacesXYZ::CAT(), spacesXYZ::adaptXYZ(), spacesRGB::RGBfromXYZ(), IsWithinMacAdamLimits()

Examples

MunsellTosRGB( c('7.6P 8.9/2.2', 'N 3/') )
##     SAMPLE_NAME      xyY.x      xyY.y      xyY.Y     RGB.R     RGB.G     RGB.B OutOfGamut
##  1 7.6P 8.9/2.2  0.3109520  0.3068719 74.6134498 231.35746 221.14207 230.35011      FALSE
##  2         N 3/  0.3101000  0.3163000  6.3911778  71.50491  71.50491  71.50491      FALSE

Convert Munsell HVC to xyY coordinates

Description

MunsellToxyY Converts Munsell HVC to xyY coordinates, by interpolating over the extrapolated Munsell renotation data

Usage

MunsellToxyY( MunsellSpec, xyC='NBS', hcinterp='bicubic', vinterp='cubic',
                     YfromV='ASTM', warn=TRUE ) 

Arguments

Details

In case hcinterp='bicubic' or vinterp='cubic' a Catmull-Rom spline is used; see the article Cubic Hermite spline. This spline has the nice property that it is local and requires at most 4 points. And if the knot spacing is uniform: 1) the resulting spline is C^1, 2) if the knots are on a line, the interpolated points are on the line too.

Value

a data.frame with these columns:

Warning

Even when vinterp='cubic' the function HVC → xyY is not C^1 on the plane V=1. This is because of a change in Value spacing: when V\ge1 the Value spacing is 1, but when V\le1 the Value spacing is 0.2.

Note

When making plots in planes of constant Value, option hcinterp='bicubic' makes fairly smooth ovals, and hcinterp='bilinear' makes polygons. The ovals are smooth even when vinterp='linear', but the function is not class C^1 at the planes of integer Value. To get a fully C^1 function (except at the neutrals and on the plane V=1), hcinterp and vinterp must be set to the defaults.

Author(s)

Jose Gama and Glenn Davis

Source

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html
https://www.rit.edu/science/munsell-color-lab
https://www.rit-mcsl.org/MunsellRenotation/all.dat
https://www.rit-mcsl.org/MunsellRenotation/real.dat

References

Judd, Deane B. The 1931 I.C.I. Standard Observer and Coordinate System for Colorimetry. Journal of the Optical Society of America. Vol. 23. pp. 359-374. October 1933.

Newhall, Sidney M., Dorothy Nickerson, Deane B. Judd. Final Report of the O.S.A. Subcommitte on the Spacing of the Munsell Colors. Journal of the Optical Society of America. Vol. 33. No. 7. pp. 385-418. July 1943.

Kelly, Kenneth L. Kasson S. Gibson. Dorothy Nickerson. Tristimulus Specification of the Munsell Book of Color from Spectrophometric Measurements National Bureau of Standards RP1549 Volume 31. August 1943.

Judd, Deane B. and Günther Wyszecki. Extension of the Munsell Renotation System to Very Dark Colors. Journal of the Optical Society of America. Vol. 46. No. 4. pp. 281-284. April 1956.

National Television System Committee. [Report and Reports of Panel No. 11, 11-A, 12-19, with Some supplementary references cited in the Reports, and the Petition for adoption of transmission standards for color television before the Federal Communications Commission] (1953)

Rheinboldt, Werner C. and John P. Menard. Mechanized Conversion of Colorimetric Data to Munsell Renotations. Journal of the Optical Society of America. Vol. 50, Issue 8, pp. 802-807. August 1960.

Wikipedia. Cubic Hermite spline. https://en.wikipedia.org/wiki/Cubic_Hermite_spline

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

xyYtoMunsell()

Examples

MunsellToxyY( '7.6P 8.9/2.2' )
##    SAMPLE_NAME  HVC.H HVC.V HVC.C      xyY.x      xyY.y      xyY.Y
##  1 7.6P 8.9/2.2  87.6   8.9   2.2  0.3109520  0.3068719 74.6134498

Calculate the Nickerson Color Difference between two Colors

Description

Calculate the Nickerson Color Difference between two colors, given in Munsell HVC; see Nickerson.

Usage

NickersonColorDifference( HVC0, HVC1, symmetric=TRUE, coeffs=c(0.4,6,3) ) 

Arguments

Details

If HVC0=H_0,V_0,C_0 and If HVC1=H_1,V_1,C_1 then the original Nickerson formula is:

NCD(HVC0,HVC1) = 0.4 C_0 \Delta H ~+~ 6 \Delta V ~+~ 3 \Delta C

where \Delta H = |H_0 - H_1| (on the circle), \Delta V = |V_0 - V_1| and \Delta C = |C_0 - C_1| . Unfortunately, if HVC0 and HVC1 are swapped, the color difference is different. The first color is considered to be the reference color and the second one is the test color. The difference is not symmetric.
Another problem is that the difference is not continuous when the second color is a neutral gray, for rectangular coordinates on a plane of constant V.

Both of these problems are fixed with a slightly modified formula:

NCD(HVC0,HVC1) = 0.4 \min(C_0,C_1) \Delta H ~+~ 6 \Delta V ~+~ 3 \Delta C

For the first formula set symmetric=FALSE and for the second formula set symmetric=TRUE.

Value

A numeric N-vector with the pairwise differences, i.e. between row i of HVC0 and row i of HVC1.

Author(s)

Jose Gama and Glenn Davis

References

Nickerson, Dorothy. The Specification of Color Tolerances. Textile Research. Vol 6. pp. 505-514. 1936.

Examples

NickersonColorDifference( '7.6P 8.9/2.2', '8P 8.2/3'  )
##  [1] 6.952

Convert RGB coordinates to Munsell HVC

Description

RGBtoMunsell Converts RGB coordinates to Munsell HVC, by interpolating over the extrapolated Munsell renotation data

Usage

RGBtoMunsell( RGB, space='sRGB', which='scene', maxSignal=255, adapt='Bradford', ... ) 

Arguments

Details

The conversion is done in these steps:

• RGB → XYZ using spacesRGB::XYZfromRGB() with the given space, which, and maxSignal

• XYZ is adapted from the white-point (with which) of space to Illuminant C, using spacesXYZ::adaptXYZ(), with the given chromatic adaptation method adapt

• XYZ → HVC using XYZtoMunsell() with ...

Value

a numeric Nx3 matrix with HVC coordinates in the rows. The rownames are copied from input RGB to output HVC, unless the rownames are NULL when they are set to the Munsell notations for HVC.
In case of error, it returns NULL.

Author(s)

Jose Gama and Glenn Davis

References

Wikipedia. sRGB. https://en.wikipedia.org/wiki/SRGB.

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

XYZtoMunsell(), spacesXYZ::CAT(), spacesXYZ::adaptXYZ(), spacesRGB::XYZfromRGB()

Examples

RGBtoMunsell( c(255,45,67) )
##                     H        V        C
##  5.4R 5.5/18 5.401135 5.477315 18.01984

RGBtoMunsell( c(255,45,67), space='Adobe' )
##                     H        V        C
##  5.9R 6.2/22 5.924749 6.214155 21.83907

Convert Munsell Value V to Luminance Factor Y, and back again

Description

Convert non-linear Munsell Value V to linear Luminance Factor Y, and back again

Usage

YfromV( V, which='ASTM' )
VfromY( Y, which='ASTM' )

Arguments

Details

'Priest' is the earliest (1920) transfer function in this package. It is implemented as:

V = sqrt(Y) ~~~~~~and~~~~~~ Y = V^2

One readily checks that when V=10, Y=100, and vice-versa. This transfer function has been implemented in colorimeters, using analog electric circuits. It is used in Hunter Lab - the precursor of CIE Lab.

'Munsell' is the next (1933) transfer function, and was proposed by Munsell's son (Alexander Ector Orr Munsell) and co-workers. It is implemented as:

V = sqrt( 1.474*Y - 0.00474*Y^2 )

Y = 50 * ( (1474 - sqrt(1474^2 - 4*4740*V^2)) / 474 )

One readily checks that when V=10, Y=100, and vice-versa. The luminance factor Y is absolute, AKA relative to the perfect reflecting diffuser.

'Priest' and 'Munsell' are included in this package for historical interest only.

The remaining three define Y as a quintic polynomial in V.

The next one historically - 'MgO' - is implemented as:

Y = (((((8404*V - 210090)*V + 2395100)*V - 2311100)*V + 10000000)*V ) / 10000000

One readily checks that when V=10, Y=102.568. This Y is larger than 100, because the authors decided to make Y relative to a clean surface of MgO, instead of the perfect reflecting diffuser. In their words:

• It should be noted that the reflectances indicated are not absolute but relative to magnesium oxide; whereas the maximum at value 10/ was formerly 100 percent, it is now 102.57. Use of this relation facilitates results and also avoids the somewhat dubious conversion to absolute scale, by permitting Y determinations with a MgO standard to be converted directly to Munsell value.

Nowadays, the perfect reflecting diffuser is preferred over MgO. For users who would like to modify this quintic as little as possible, with the perfect reflecting diffuser in mind (going back to 'MUNSELL'), I offer 'OSA', which is given by this quintic of my own design

Y = (((((8404*V - 210090)*V + 2395100)*V - 2311100)*V + 10000000)*V ) / 10256800

ASTM had a similar modification in mind, but did it a little differently by scaling each coefficient. 'ASTM' is given by this quintic:

Y = ( ((((81939*V - 2048400)*V + 23352000)*V - 22533000)*V + 119140000)*V ) / 1.e8

One readily checks that when V=10, Y=100 exactly (for both 'OSA' and 'ASTM').

The inverses - from Y to V - of all 3 quintics are implemented as 3 splinefun()s at a large number (about 300) of points. These inverses are both fast and accurate. The round-trip Y → V → Y is accurate to 7 digits after the decimal. The round-trip V → Y → V is accurate to 8 digits after the decimal.

Value

a numeric vector the same length as the input

Note

The quintic functions 'ASTM' and 'OSA' are very close. They agree at the endpoints 0 and 10 exactly, and the largest difference is near V=6.767 where they differ by about 0.0007.

Author(s)

Glenn Davis

References

Priest, I. G. Gibson, K. S. and McNicholas, H. J. An Examination of the Munsell Color System. I. Spectral and and Total Reflection and the Munsell Scale of Value. Technologic Papers of the Bureau of Standards, No. 167. pp. 1-33. Washington D.C. 1920.

Munsell, A. E. O., L. L. Sloan, and I. H. Godlove. Neutral Value Scales. I. Munsell Neutral Value Scale. Journal of the Optical Society of America. Vol. 23. Issue 11. pp. 394-411. November 1933.

Newhall, Sidney M., Dorothy Nickerson, Deane B. Judd. Final Report of the O.S.A. Subcommitte on the Spacing of the Munsell Colors. Journal of the Optical Society of America. Vol. 33. No. 7. pp. 385-418. July 1943.

ASTM D 1535-08. Standard Practice for Specifying Color by the Munsell System. 2008

See Also

MunsellToxyY(), xyYtoMunsell()

Examples

VfromY( c(0,50,100) )
##  [1]  0.00000  7.53772 10.00000

Convert XYZ coordinates to Munsell HVC

Description

XYZtoMunsell Convert XYZ coordinates to Munsell HVC, by interpolating over the Munsell renotation data

Usage

XYZtoMunsell( XYZ, ... ) 

Arguments

Details

the function calls XYZ2xyY() and xyYtoMunsell().

The conversion is done in these steps:

• XYZ → xyY using spacesXYZ::xyYfromXYZ()

• xyY → HVC using xyYtoMunsell() and ...

Value

an Nx3 matrix with Munsell HVC in the rows. The rownames are copied from input to output, unless the rownames are NULL when they are set to the Munsell notations for HVC.
In case of error, it returns NULL.

Author(s)

Jose Gama and Glenn Davis

References

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

MunsellToXYZ(), spacesXYZ::xyYfromXYZ()

Examples

XYZtoMunsell( c(31.0897, 30.6510, 74.613450) )
##                      H        V        C
## 5.4PB 6.1/9.4 75.43786 6.117631 9.416488

Plot Curves of Constant Munsell Hue and Chroma

Description

Plot Curves of Constant Munsell Hue and Chroma

Usage

plotLociHC( value=5, hue=seq(2.5,100,by=2.5), chroma='auto', coords='xy',
                        main="Value %g/", est=FALSE, ... ) 

Arguments

Details

The plot limits (xlim and ylim) are set to include all points where the Hue radials intersect the Chroma ovoids, plus the white point.
If value is one of {0.2,0.4,0.6,0.8,1,2,3,4,5,6,7,8,9,10} then published points from real.dat are plotted with filled black points (real points), and extrapolated points from all.dat are drawn with open circles (unreal points).

Value

TRUE for success and FALSE for failure.

Note

The option hcinterp='bicubic' makes fairly smooth ovoids, and hcinterp='bilinear' makes 40-sided polygons (when coords='xy'). Compare with the plots in Newhall et. al. (1943), Judd, et. al. (1956), and Judd, et. al. (1975) p. 263.

Author(s)

Glenn Davis

References

Newhall, Sidney M., Dorothy Nickerson, Deane B. Judd. Final Report of the O.S.A. Subcommitte on the Spacing of the Munsell Colors. Journal of the Optical Society of America. Vol. 33. No. 7. pp. 385-418. July 1943.

Judd, Deane B. and Günther Wyszecki. Extension of the Munsell Renotation System to Very Dark Colors. Journal of the Optical Society of America. Vol. 46. No. 4. pp. 281-284. April 1956.

Judd, Deane B. and Günther Wyszecki. Color in Business, Science, and Industry. 3rd edition. John Wiley & Sons. 1975.

See Also

MunsellToxyY(), HueNumberFromString()

Plot Colored Patches for a fixed Munsell Hue

Description

This plot simulates a page from the Munsell Book of Color. The colors are best viewed on a display calibrated for the RGB space given as the second argument.

Usage

plotPatchesH( hue, space='sRGB', adapt='Bradford', background='gray50',
                        main="Hue %s  (H=%g)      [%s   adapt=%s]",
                        value=NULL, chroma=NULL, ... ) 

Arguments

Details

If chroma=NULL, for the closest discrete Hue in real.dat, the patches in real.dat are transformed to xyY using simple lookup with no interpolation. These are then tested against the MacAdam Limits for Illuminant C using IsWithinMacAdamLimits(). The patches outside the limits are discarded, and the maximum Chroma of the remaining patches, which is always an even integer, determines chroma.
Patches inside the MacAdam Limits can still be outside the RGB cube; those patches are drawn in outline only, and with the clamped RGB coordinates printed inside.

Value

TRUE for success and FALSE for failure.

Author(s)

Glenn Davis

See Also

MunsellToRGB(), HueNumberFromString(), IsWithinMacAdamLimits(), spacesRGB::installRGB()

Round a Given Munsell HVC to the Closest Sample in One or More Books of Samples

Description

The functions in this package compute Munsell HVC coordinates with high precision. When reporting the Munsell notation it is often desirable, for historical consistency or other reasons, to report a notation that is actually appears in one or more published books of Munsell samples. This rounding operation requires exact knowledge of such books. We use a paper by Ferguson, which gives the contents of books on these fields: soil, rocks, beads, and plants. It also includes The New Munsell Student Color Set, see References.

Usage

roundHVC( HVC, books )

Arguments

Details

First, the set of samples over all selected books is formed. Then the closest sample in this set to the given notation is found. For the color distance, the function NickersonColorDifference() is used. Unfortunately, the particular coefficients in this difference equation can lead to large regions of Munsell color space with exact ties for the two closest samples. These exact ties make the final result unpredictable and sometime unintuitive. As a tie-breaker, a very small multiple (1.e-6) of plain Eucliden distance is added to the Nickerson difference, which has proven effective.

Value

A data.frame with a N rows and these columns:

The row names are set to the row names of HVC. But if these are NULL they are set to the Munsell notation of the input HVC. Finally, if these row names have duplicates, they are set to 1:N.

Acknowledgements

The conversion of the book data to Supplement1_3.6.2024.csv was done by Willie Ondricek, who provided all the motivation for this function. He also kindly provided photographs of the soil book, and much other material.

Author(s)

Glenn Davis

Source

The data on books of samples is provide in .../munsellinterpol/inst/extdata/Supplement1_3.6.2024.csv. This was converted from the original file yjfa_a_11710256_sm0001.docx which is Online Supplement #1 from Ferguson.

The sample counts in the 5 books are:

The union of all 5 books has 869 samples.

References

Ferguson, Jonathan. Munsell notations and color names: Recommendations for archaeological practice. Journal of Field Archaeology. 39:4. 327-335. (2014). Online Supplement #1.

Long, J. T. The New Munsell Student Color Set. New York: Fairchild Books. 2011.

Munsell Color. Munsell Soil-Color Charts. Grand Rapids, MI: 2009.

Munsell Color. Geological Rock-Color Chart. GrandRapids, MI: 2009.

Munsell Color. Munsell Bead Color Book. Grand Rapids, MI: 2012.

Munsell Color. Munsell Color Charts for Plant Tissues. New Windsor, NY: 1977.

Examples

## search the soil book for the best match for 3 samples
roundHVC( c("7.7YR 3.4/6.1", "2.6PB 6.1/4.5", "N 6.6/" ), books='soil' )

##               HVC.H HVC.V HVC.C ISCC-NBS Name MunsellRounded Ferguson Name
## 7.7YR 3.4/6.1  17.7   3.4   6.1  strong brown      7.5YR 4/6  Strong brown
## 2.6PB 6.1/4.5  72.6   6.1   4.5     pale blue        5PB 6/1   Bluish gray
## N 6.6/          0.0   6.6   0.0    light gray           N 7/    Light gray

## The middle sample has a poor match, since "purplish-blue" with Chroma=4.5
## is not well-matched by soil color samples.
## Search again, but this time in all 5 books.

roundHVC( c("7.7YR 3.4/6.1", "2.6PB 6.1/4.5", "N 6.6/" ), books='s,b,r,p,n' )

##               HVC.H HVC.V HVC.C ISCC-NBS Name MunsellRounded Ferguson Name
## 7.7YR 3.4/6.1  17.7   3.4   6.1  strong brown      7.5YR 4/6  Strong brown
## 2.6PB 6.1/4.5  72.6   6.1   4.5     pale blue        5PB 6/4     Pale blue
## N 6.6/          0.0   6.6   0.0    light gray           N 7/    Light gray

## This time, for the middle sample, a better match was found.
## The other 2 sample are unchanged.

Convert sRGB coordinates to Munsell HVC

Description

Converts non-linear sRGB coordinates to Munsell HVC, by interpolating over the extrapolated Munsell renotation data

Usage

sRGBtoMunsell( sRGB, maxSignal=255, ... ) 

Arguments

Details

The conversion is done in these steps:

• sRGB → XYZ using spacesXYZ::XYZfromRGB() with the given maxSignal

• XYZ is adapted from Illuminant D65 (from the sRGB standard) to Illuminant C, using spacesXYZ::adaptXYZ() with the Bradford chromatic adaptation method

• XYZ → HVC using XYZtoMunsell() and the given ...

Value

a numeric Nx3 matrix with HVC coordinates in the rows. The rownames are copied from input to output, unless the rownames are NULL when they are set to the Munsell notations for HVC.
In case of error, it returns NULL.

Note

The more general function RGBtoMunsell() also performs this conversion. This function has the advantage that it takes a little less time, since the CAT (using the Bradford method) is precomputed during base::.onLoad(). But it has the disadvantage that the chromatic adaptation method cannot be changed.

Author(s)

Jose Gama and Glenn Davis

References

Wikipedia. sRGB. https://en.wikipedia.org/wiki/SRGB.

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

RGBtoMunsell(), XYZtoMunsell(), spacesXYZ::CAT(), spacesXYZ::adaptXYZ(), spacesXYZ::XYZfromRGB()

Examples

sRGBtoMunsell( c(255,45,67) )
##                     H        V        C
##  5.4R 5.5/18 5.401135 5.477315 18.01984

sRGBtoMunsell( c(1,0,1), maxSignal=1 )
##                 H        V        C
##  8P 6/26 87.98251 5.981297 25.64534

Convert xyY coordinates to Munsell HVC

Description

xyYtoMunsell Convert xyY coordinates to Munsell HVC, by interpolating over the extrapolated Munsell renotation data.
HVC \to xyY is the forward direction, and xyY \to HVC is the inverse direction. This inversion requires requires root-finding, which is done using rootSolve::multiroot().

Usage

xyYtoMunsell( xyY, xyC='NBS', hcinterp='bicubic', vinterp='cubic',
                     VfromY='ASTM', rtol=1.e-8, atol=1.e-6, warn=TRUE, perf=FALSE ) 

Arguments

Details

See MunsellToxyY() and the User Guide - Appendix C.

Value

a data.frame with N rows and these columns:

If perf is TRUE then there are these additional columns:

Warning

Even when vinterp='cubic' the function xyY → HVC is not C^1 on the plane V=1. This is because of a change in Value spacing: when V\ge1 the Value spacing is 1, but when V\le1 the Value spacing is 0.2.

Author(s)

Jose Gama and Glenn Davis

Source

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html
https://www.rit.edu/science/munsell-color-lab
https://www.rit-mcsl.org/MunsellRenotation/all.dat
https://www.rit-mcsl.org/MunsellRenotation/real.dat

References

Judd, Deane B. The 1931 I.C.I. Standard Observer and Coordinate System for Colorimetry. Journal of the Optical Society of America. Vol. 23. pp. 359-374. October 1933.

Newhall, Sidney M., Dorothy Nickerson, Deane B. Judd. Final Report of the O.S.A. Subcommitte on the Spacing of the Munsell Colors. Journal of the Optical Society of America. Vol. 33. No. 7. pp. 385-418. July 1943.

Kelly, Kenneth L. Kasson S. Gibson. Dorothy Nickerson. Tristimulus Specification of the Munsell Book of Color from Spectrophometric Measurements National Bureau of Standards RP1549 Volume 31. August 1943.

Judd, Deane B. and Günther Wyszecki. Extension of the Munsell Renotation System to Very Dark Colors. Journal of the Optical Society of America. Vol. 46. No. 4. pp. 281-284. April 1956.

Paul Centore 2014 The Munsell and Kubelka-Munk Toolbox https://www.munsellcolourscienceforpainters.com/MunsellAndKubelkaMunkToolbox/MunsellAndKubelkaMunkToolbox.html

See Also

MunsellToxyY(), rootSolve::multiroot(), microbenchmark::get_nanotime()

Examples

xyYtoMunsell(c(0.310897, 0.306510, 74.613450))
##       xyY.1     xyY.2     xyY.3     HVC.H     HVC.V     HVC.C    SAMPLE_NAME
## 1  0.310897  0.306510 74.613450 87.541720  8.900000  2.247428   7.5P 8.9/2.2