Converting saturated, bright, dark, or near-gray RGB colors to Munsell colors get an error that the specification doesn't exists on Munsell Renotation System data.

[lulunac27a]

Description

I got an error when converting saturated RGB colors (RGB 0,0,1, blue) to Munsell color saying the specification doesn't exists on Munsell Renotation System data. I also get errors that near-gray RGB colors says chroma is not in domain from 2 to 50, and bright RGB colors like yellow (RGB 1,1,0) get an error that maximum number of iterations reached and another error that converting black color (RGB 0,0,0) get an error that the value is not in domain of 1 to 10.

Errors:

ValueError: "[ 10. 3. 22. 1.]" specification does not exists in "Munsell Renotation System" data!
rgb=[0,0,1] xyz=colour.sRGB_to_XYZ(rgb) xyy=colour.XYZ_to_xyY(xyz) munsell=colour.xyY_to_munsell_colour(xyy) print(munsell)
AssertionError: "array([ 7.73987341, 5.23531075, 0.656444 , 4. ])" specification chroma must be normalised to domain [2, 50]!
rgb=[0.5,0.5,0.5] xyz=colour.sRGB_to_XYZ(rgb) xyy=colour.XYZ_to_xyY(xyz) munsell=colour.xyY_to_munsell_colour(xyy) print(munsell)
AssertionError: "[ 5.37774567 10. nan 2. ]" specification value must be normalised to domain [1, 9]!
rgb=[1,1,1] xyz=colour.sRGB_to_XYZ(rgb) xyy=colour.XYZ_to_xyY(xyz) munsell=colour.xyY_to_munsell_colour(xyy) print(munsell)
RuntimeError: Maximum inner iterations count reached without convergence!
rgb=[1,1,0] xyz=colour.sRGB_to_XYZ(rgb) xyy=colour.XYZ_to_xyY(xyz) munsell=colour.xyY_to_munsell_colour(xyy) print(munsell)
AssertionError: "0.0" value must be normalised to domain [1, 10]!
rgb=[0,0,0] xyz=colour.sRGB_to_XYZ(rgb) xyy=colour.XYZ_to_xyY(xyz) munsell=colour.xyY_to_munsell_colour(xyy) print(munsell)

Code for Reproduction

===============================================================================
*                                                                             *
*   Interpreter :                                                             *
*       python : 3.9.15 | packaged by conda-forge | (main, Nov 22 2022,       *
*   08:55:37)                                                                 *
*                [Clang 14.0.6 ]                                              *
*                                                                             *
*   colour-science.org :                                                      *
*       colour : 0.4.2                                                        *
*                                                                             *
*   Runtime :                                                                 *
*       imageio : 2.25.0                                                      *
*       matplotlib : 3.6.3                                                    *
*       networkx : 3.0                                                        *
*       numpy : 1.24.1                                                        *
*       pandas : 1.5.3                                                        *
*       scipy : 1.10.0                                                        *
*       tqdm : 4.64.1                                                         *
*                                                                             *
===============================================================================

Exception Message

/Users/lulunac/opt/anaconda3/lib/python3.9/site-packages/colour/utilities/verbose.py:266: ColourUsageWarning: "array([ 0.15001662,  0.06000665,  0.0722    ])" is not within "MacAdam" limits for illuminant "C"!
  warn(*args, **kwargs)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_from_renotation(specification)
   1755 
-> 1756         return MUNSELL_COLOURS_ALL[int(index[0])][1]
   1757     except Exception:

TypeError: only size-1 arrays can be converted to Python scalars

During handling of the above exception, another exception occurred:

ValueError                                Traceback (most recent call last)
/var/folders/92/n6cd988d2z9cdrxst_9dwkt00000gn/T/ipykernel_1705/2990441278.py in <module>
      1 rgb=[0,0,1]
      2 xyz=colour.sRGB_to_XYZ(rgb)
      3 xyy=colour.XYZ_to_xyY(xyz)
----> 4 munsell=colour.xyY_to_munsell_colour(xyy)

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_to_munsell_colour(xyY, hue_decimals, value_decimals, chroma_decimals)
   1458 
   1459     specification = to_domain_10(
-> 1460         xyY_to_munsell_specification(xyY), _munsell_scale_factor()
   1461     )
   1462     shape = list(specification.shape)

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_to_munsell_specification(xyY)
   1404     shape = list(xyY.shape)
   1405 
-> 1406     specification = [
   1407         _xyY_to_munsell_specification(a) for a in xyY.reshape([-1, 3])
   1408     ]

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in <listcomp>(.0)
   1405 
   1406     specification = [
-> 1407         _xyY_to_munsell_specification(a) for a in xyY.reshape([-1, 3])
   1408     ]
   1409 

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in _xyY_to_munsell_specification(xyY)
   1191 
   1192             with domain_range_scale("ignore"):
-> 1193                 x_inner, y_inner, _Y_inner = _munsell_specification_to_xyY(
   1194                     [hue_inner, value, chroma_current, code_inner]
   1195                 )

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in _munsell_specification_to_xyY(specification)
    902         else [hue, value_minus, chroma, code]
    903     )
--> 904     x_minus, y_minus = tsplit(munsell_specification_to_xy(specification_minus))
    905 
    906     specification_plus = as_float_array(

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in munsell_specification_to_xy(specification)
   2683             x_minus, y_minus = CCS_ILLUMINANT_MUNSELL
   2684         else:
-> 2685             x_minus, y_minus = xy_from_renotation_ovoid(
   2686                 [hue, value, chroma_minus, code]
   2687             )

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xy_from_renotation_ovoid(specification)
   2395 
   2396         specification_minus = (hue_minus, value, chroma, code_minus)
-> 2397         x_minus, y_minus, Y_minus = xyY_from_renotation(specification_minus)
   2398         rho_minus, phi_minus, _z_minus = cartesian_to_cylindrical(
   2399             [x_minus - x_grey, y_minus - y_grey, Y_minus]

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_from_renotation(specification)
   1756         return MUNSELL_COLOURS_ALL[int(index[0])][1]
   1757     except Exception:
-> 1758         raise ValueError(
   1759             f'"{specification}" specification does not exists in '
   1760             '"Munsell Renotation System" data!'

ValueError: "[ 10.   3.  22.   1.]" specification does not exists in "Munsell Renotation System" data!
---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
/var/folders/92/n6cd988d2z9cdrxst_9dwkt00000gn/T/ipykernel_1705/2062133454.py in <module>
      1 rgb=[0.5,0.5,0.5]
      2 xyz=colour.sRGB_to_XYZ(rgb)
      3 xyy=colour.XYZ_to_xyY(xyz)
----> 4 munsell=colour.xyY_to_munsell_colour(xyy)
      5 print(munsell)

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_to_munsell_colour(xyY, hue_decimals, value_decimals, chroma_decimals)
   1465     munsell_colour = np.reshape(
   1466         np.array(
-> 1467             [
   1468                 munsell_specification_to_munsell_colour(a, *decimals)
   1469                 for a in specification.reshape([-1, 4])

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in <listcomp>(.0)
   1466         np.array(
   1467             [
-> 1468                 munsell_specification_to_munsell_colour(a, *decimals)
   1469                 for a in specification.reshape([-1, 4])
   1470             ]

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in munsell_specification_to_munsell_colour(specification, hue_decimals, value_decimals, chroma_decimals)
   1690 
   1691         chroma = round(chroma, chroma_decimals)
-> 1692         attest(
   1693             2 <= chroma <= 50,
   1694             f'"{specification!r}" specification chroma must be normalised to '

~/opt/anaconda3/lib/python3.9/site-packages/colour/utilities/common.py in attest(condition, message)
    382 
    383     if not condition:
--> 384         raise AssertionError(message)
    385 
    386 

AssertionError: "array([ 7.73987341,  5.23531075,  0.656444  ,  4.        ])" specification chroma must be normalised to domain [2, 50]!
/Users/lulunac/opt/anaconda3/lib/python3.9/site-packages/colour/utilities/verbose.py:266: ColourUsageWarning: "array([ 0.31271591,  0.32900148,  1.        ])" is not within "MacAdam" limits for illuminant "C"!
  warn(*args, **kwargs)
/Users/lulunac/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py:1293: RuntimeWarning: divide by zero encountered in scalar divide
  (rho_input / rho_current) ** iterations_inner
/Users/lulunac/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py:1292: RuntimeWarning: invalid value encountered in scalar multiply
  chroma_inner = (
---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
/var/folders/92/n6cd988d2z9cdrxst_9dwkt00000gn/T/ipykernel_1705/3006693157.py in <module>
      1 rgb=[1,1,1]
      2 xyz=colour.sRGB_to_XYZ(rgb)
      3 xyy=colour.XYZ_to_xyY(xyz)
----> 4 munsell=colour.xyY_to_munsell_colour(xyy)
      5 print(munsell)

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_to_munsell_colour(xyY, hue_decimals, value_decimals, chroma_decimals)
   1458 
   1459     specification = to_domain_10(
-> 1460         xyY_to_munsell_specification(xyY), _munsell_scale_factor()
   1461     )
   1462     shape = list(specification.shape)

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_to_munsell_specification(xyY)
   1404     shape = list(xyY.shape)
   1405 
-> 1406     specification = [
   1407         _xyY_to_munsell_specification(a) for a in xyY.reshape([-1, 3])
   1408     ]

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in <listcomp>(.0)
   1405 
   1406     specification = [
-> 1407         _xyY_to_munsell_specification(a) for a in xyY.reshape([-1, 3])
   1408     ]
   1409 

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in _xyY_to_munsell_specification(xyY)
   1305 
   1306             with domain_range_scale("ignore"):
-> 1307                 x_inner, y_inner, _Y_inner = _munsell_specification_to_xyY(
   1308                     specification_inner
   1309                 )

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in _munsell_specification_to_xyY(specification)
    902         else [hue, value_minus, chroma, code]
    903     )
--> 904     x_minus, y_minus = tsplit(munsell_specification_to_xy(specification_minus))
    905 
    906     specification_plus = as_float_array(

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in munsell_specification_to_xy(specification)
   2683             x_minus, y_minus = CCS_ILLUMINANT_MUNSELL
   2684         else:
-> 2685             x_minus, y_minus = xy_from_renotation_ovoid(
   2686                 [hue, value, chroma_minus, code]
   2687             )

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xy_from_renotation_ovoid(specification)
   2345         hue, value, chroma, code = specification
   2346 
-> 2347         attest(
   2348             1 <= value <= 9,
   2349             f'"{specification}" specification value must be normalised to '

~/opt/anaconda3/lib/python3.9/site-packages/colour/utilities/common.py in attest(condition, message)
    382 
    383     if not condition:
--> 384         raise AssertionError(message)
    385 
    386 

AssertionError: "[  5.37774567  10.                  nan   2.        ]" specification value must be normalised to domain [1, 9]!
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
/var/folders/92/n6cd988d2z9cdrxst_9dwkt00000gn/T/ipykernel_1705/799062424.py in <module>
      1 rgb=[1,1,0]
      2 xyz=colour.sRGB_to_XYZ(rgb)
      3 xyy=colour.XYZ_to_xyY(xyz)
----> 4 munsell=colour.xyY_to_munsell_colour(xyy)
      5 print(munsell)

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_to_munsell_colour(xyY, hue_decimals, value_decimals, chroma_decimals)
   1458 
   1459     specification = to_domain_10(
-> 1460         xyY_to_munsell_specification(xyY), _munsell_scale_factor()
   1461     )
   1462     shape = list(specification.shape)

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_to_munsell_specification(xyY)
   1404     shape = list(xyY.shape)
   1405 
-> 1406     specification = [
   1407         _xyY_to_munsell_specification(a) for a in xyY.reshape([-1, 3])
   1408     ]

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in <listcomp>(.0)
   1405 
   1406     specification = [
-> 1407         _xyY_to_munsell_specification(a) for a in xyY.reshape([-1, 3])
   1408     ]
   1409 

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in _xyY_to_munsell_specification(xyY)
   1284 
   1285             if iterations_inner > iterations_maximum_inner:
-> 1286                 raise RuntimeError(
   1287                     "Maximum inner iterations count reached "
   1288                     "without convergence!"

RuntimeError: Maximum inner iterations count reached without convergence!
/Users/lulunac/opt/anaconda3/lib/python3.9/site-packages/colour/utilities/verbose.py:266: ColourUsageWarning: "array([ 0.3127,  0.329 ,  0.    ])" is not within "MacAdam" limits for illuminant "C"!
  warn(*args, **kwargs)
/Users/lulunac/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py:1105: RuntimeWarning: divide by zero encountered in scalar divide
  XYZ_r = np.array([(1 / Y_r) * X_r, 1, (1 / Y_r) * Z_r])
/Users/lulunac/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py:1105: RuntimeWarning: invalid value encountered in scalar multiply
  XYZ_r = np.array([(1 / Y_r) * X_r, 1, (1 / Y_r) * Z_r])
---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
/var/folders/92/n6cd988d2z9cdrxst_9dwkt00000gn/T/ipykernel_1705/33299363.py in <module>
      1 rgb=[0,0,0]
      2 xyz=colour.sRGB_to_XYZ(rgb)
      3 xyy=colour.XYZ_to_xyY(xyz)
----> 4 munsell=colour.xyY_to_munsell_colour(xyy)
      5 print(munsell)

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_to_munsell_colour(xyY, hue_decimals, value_decimals, chroma_decimals)
   1458 
   1459     specification = to_domain_10(
-> 1460         xyY_to_munsell_specification(xyY), _munsell_scale_factor()
   1461     )
   1462     shape = list(specification.shape)

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in xyY_to_munsell_specification(xyY)
   1404     shape = list(xyY.shape)
   1405 
-> 1406     specification = [
   1407         _xyY_to_munsell_specification(a) for a in xyY.reshape([-1, 3])
   1408     ]

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in <listcomp>(.0)
   1405 
   1406     specification = [
-> 1407         _xyY_to_munsell_specification(a) for a in xyY.reshape([-1, 3])
   1408     ]
   1409 

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in _xyY_to_munsell_specification(xyY)
   1132         hue_angle_current = hue_to_hue_angle([hue_current, code_current])
   1133 
-> 1134         chroma_maximum = maximum_chroma_from_renotation(
   1135             [hue_current, value, code_current]
   1136         )

~/opt/anaconda3/lib/python3.9/site-packages/colour/notation/munsell.py in maximum_chroma_from_renotation(hue_and_value_and_code)
   2568         return 0
   2569 
-> 2570     attest(
   2571         1 <= value <= 10,
   2572         f'"{value}" value must be normalised to domain [1, 10]!',

~/opt/anaconda3/lib/python3.9/site-packages/colour/utilities/common.py in attest(condition, message)
    382 
    383     if not condition:
--> 384         raise AssertionError(message)
    385 
    386 

AssertionError: "0.0" value must be normalised to domain [1, 10]!

Environment Information

defaultdict(dict,
            {'Interpreter': {'python': '3.9.15 | packaged by conda-forge | (main, Nov 22 2022, 08:55:37) \n[Clang 14.0.6 ]'},
             'colour-science.org': {'colour': '0.4.2'},
             'Runtime': {'imageio': '2.25.0',
              'matplotlib': '3.6.3',
              'networkx': '3.0',
              'numpy': '1.24.1',
              'pandas': '1.5.3',
              'scipy': '1.10.0',
              'tqdm': '4.64.1'}})

[KelSolaar]

Hi @lulunac27a,

The behaviour you see is expected, the Munsell Renotation System is first and foremost a physical dataset that was created with real paint thus its gamut is very irregular:

The consequence is that many "digital" colours simply do not exist in it, e.g. pure blue, pure red or pure black. I'm curious about the near-grey values though, it would be useful if you could send over the ones you tried that failed.

Cheers,

Thomas