PR: Varnish "Recommendation ITU-T H.273" Implementation

[KelSolaar]

Summary

This PR polishes the Recommendation ITU-T H.273 implementation from #987.

• FFmpeg enums are not defining the dictionary keys anymore, the coupling is now looser but it should not be driven by names from another software.
• Exposed the core objects to the base namespace.
• I added definitions to describe the code points:

>>> colour.COLOUR_PRIMARIES_ITUTH273.keys()
dict_keys([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 22, 23])
>>> colour.COLOUR_PRIMARIES_ITUTH273.keys()
>>> description = colour.models.describe_video_signal_colour_primaries(1)
===============================================================================
*                                                                             *
*   Colour Primaries: 1                                                       *
*   -------------------                                                       *
*                                                                             *
*   Primaries        : [[ 0.64  0.33]                                         *
*                       [ 0.3   0.6 ]                                         *
*                       [ 0.15  0.06]]                                        *
*   Whitepoint       : [ 0.3127  0.329 ]                                      *
*   Whitepoint Name  : D65                                                    *
*   NPM              : [[ 0.4123908   0.35758434  0.18048079]                 *
*                       [ 0.21263901  0.71516868  0.07219232]                 *
*                       [ 0.01933082  0.11919478  0.95053215]]                *
*   NPM -1           : [[ 3.24096994 -1.53738318 -0.49861076]                 *
*                       [-0.96924364  1.8759675   0.04155506]                 *
*                       [ 0.05563008 -0.20397696  1.05697151]]                *
*   FFmpeg Constants : ['AVCOL_PRI_BT709', 'BT709']                           *
*                                                                             *
===============================================================================
>>> colour.TRANSFER_CHARACTERISTICS_ITUTH273.keys()
dict_keys([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19])
>>> description = colour.models.describe_video_signal_transfer_characteristics(1)
===============================================================================
*                                                                             *
*   Transfer Characteristics: 1                                               *
*   ---------------------------                                               *
*                                                                             *
*   Function         : <function oetf_BT709 at 0x165bb3550>                   *
*   FFmpeg Constants : ['AVCOL_TRC_BT709', 'BT709']                           *
*                                                                             *
===============================================================================
>>> colour.MATRIX_COEFFICIENTS_ITUTH273.keys()
dict_keys([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15])
>>> description = colour.models.describe_video_signal_matrix_coefficients(1)
===============================================================================
*                                                                             *
*   Matrix Coefficients: 1                                                    *
*   ----------------------                                                    *
*                                                                             *
*   Matrix Coefficients : [ 0.2126  0.0722]                                   *
*   FFmpeg Constants    : ['AVCOL_SPC_BT709', 'BT709']                        *
*                                                                             *
===============================================================================

• Unit tests have been implemented whilst ensuring that the domain-range scale support works.
• Various transfer functions have been moved around.
• Bibliography and keys are updated.
• Updated and cleaned-up the docstrings, removed redundant info.
• Added examples and docs.
• Etc...

Preflight

Code Style and Quality

• Unit tests have been implemented and passed.
• Mypy static checking has been run and passed.
• Pre-commit hooks have been run and passed.
• New transformations have been added to the Automatic Colour Conversion Graph.
• New transformations have been exported to the relevant namespaces, e.g. colour, colour.models.

Documentation

• New features are documented along with examples if relevant.
• The documentation is Sphinx and numpydoc compliant.

[KelSolaar]

@fxthomas for VIS!

[coveralls]

Coverage increased (+0.003%) to 99.839% when pulling 243e8e4 on feature/itu_t_h273 into 2dc8afc on develop.

[fxthomas]

Nice, thank you for taking the time to consolidate these! Looks good to me, and I'll take notes of the changes you did for the next time I need to contribute ;)