Munsell Inversion Data

This repository provides fundamental data for conversion from some color spaces (e.g. RGB) to Munsell color system. All the data are generated with color library dufy.

Copying

I don't claim any rights on the generated data (i.e. files in dat/ directory), which are all based on the Munsell renotation data. The other codes are under the MIT lincense.

RGB-to-Munsell binary data

• sRGB: mid-srgb-d65.dat
• sRGB [D50]: mid-srgb-d50.dat
• Adobe RGB: mid-adobergb-d65.dat
• Adobe RGB [D50]: mid-adobergb-d50.dat

Structure

Each of these files is 256 * 256 * 256 * 32 bit (≒ 64MB) binary data, which is a table of conversion from hex (#000000 to #FFFFFF) to Munsell color. Each 32-bit data gives a corresponding Munsell color in hue-value-chroma format in big-endian byte-order:

1-bit	1-bit	10-bit	10-bit	10-bit
0	0	0000000000	0000000000	0000000000
F	-	H	V	C

F: flag of large transformation error:

This flag means that the transformation error is slightly large, which is estimated as follows:

error_diagram digraph G { graph [ labelloc = "t", label = "Transformation Error e.g. in the case of sRGB(D65)", fontsize = 16 ]; node [shape = "box", fontname = "helvetica"] munsell [ label = "Munsell Color" ] lchab [ label = "LCh(ab)\n illuminant C" ] xyzc [label = "XYZ\nilluminant C" ] xyzd65a [label = "XYZ\nilluminant D65" ] xyzd65b [label = "XYZ\nilluminant D65" ] hex [label = "Hex"]

{rank=same; munsell; hex;} {rank=same; xyzd65a; xyzd65b;}

munsell -> lchab [label = "dufy:mhvc-to-lchab-illum-c"] hex -> xyzd65b lchab -> xyzc xyzc -> xyzd65a [label = "Bradford" ]

xyzd65b -> xyzd65a [ label = "Error", dir = both, color = palevioletred3, fontcolor = palevioletred3 ]

} error_diagram

The error is evaluated by ΔE^∗_ab: If ΔE^∗_ab ≥ 1.0, the flag is 1.

H: quantized hue in {0, 1, ..., 999}

H corresponds to Munsell hue string as follows:

H	Hue String
0 to 100	10RP (=0R) to 10R (=0YR)
100 to 200	10R (=0YR) to 10YR (=0Y)
...	...
900 to 999	10P (=0RP) to 9.9RP

V: quantized value in {0, 1, ..., 1000}

Munsell value in [0, 10] is quantized to V by 0.01.

C: quantized chroma in {0, 1, ..., 500}

Munsell chroma in [0, 50] is quantized to C by 0.1.

Information about accuracy

The transformation error is evaluated as described above. The general statistics is as follows:

RGB space	Num. of nodes s.t. Δ E∗ab ≥ 1	Mean Δ E∗ab	Max. Δ E∗ab	Mean Δ E∗00	Max. Δ E∗00
sRGB (D65)	0	0.1992	0.9855	0.09047	0.7190
sRGB (D50)	287	0.2006	1.167	0.09395	0.6750
Adobe RGB (D65)	28502	0.2188	1.346	0.09073	1.155
Adobe RGB (D50)	19199	0.2202	1.325	0.09397	1.112

Note: as is clear from the above diagram, the error here means the color difference not to true colors but to the return values of dufy:mhvc-to-lchab-illum-c. For more information about the converter, see https://github.com/privet-kitty/dufy.

LCh_ab-to-Munsell text data

• Medium set [C]: lchab-to-munsell.dat
• Large set [C]: lchab-to-munsell-large.dat
• Medium set [D65]: lchab-to-munsell-d65.dat
• Large set [D65]: lchab-to-munsell-d65-large.dat
• Medium set [D50]: lchab-to-munsell-d50.dat
• Large set [D50]: lchab-to-munsell-d50-large.dat

Structure

These files are space-separated data of LCh_ab and Munsell notations:

   L*      C*ab       hab         H         V         C      H360
    2        10         0   6.6121R   0.19144   1.49703   23.8035
    2        15         0   6.7657R   0.19144   2.33540   24.3564
    2        20         0   7.0775R   0.19144   3.34647   25.4789
    2        10         9  0.6621YR   0.19144   1.52596   38.3835
    2        15         9  0.8897YR   0.19144   2.37836   39.2031
 ...      ...       ...       ...       ...       ...       ...    

Here H360 is a numerical form of Munsell hue notation:

H360	H
0 to 36	10RP (=0R) to 10R (=0YR)
36 to 72	10R (=0YR) to 10YR (=0Y)
...	...
324 to 360	10P (=0RP) to 10RP (= 0R)

Since the Munsell renotation data is measured under illuminant C, the data sets of illuminant D65 and D50 are generated by Bradford transformation. Hence you should use those of illuminant C, if you need raw data.

For each illuminant there are two data sets of different size:

Data set	L∗	C∗ab	Hab
Medium	10, 20, 30, ... , 100	5, 10, 15, ..., max. in MRD	0, 9, 18, ..., 351
Large	2, 4, 6, ... , 100	5, 10, 15, ..., max. in MRD	0, 3, 6, ..., 357

Information about accuracy

Each data is accurate (i.e. significant digits = display digits) as an inversion of dufy:mhvc-to-lchab-illum-c. Therefore the true errors depend on it. For more information, see https://github.com/privet-kitty/dufy.