"""
Y'CbCr Colour Encoding
======================
Define the *Y'CbCr* colour encoding related attributes and objects.
- :attr:`colour.WEIGHTS_YCBCR`
- :attr:`colour.SCALES_YCBCR`
- :func:`colour.matrix_YCbCr`
- :func:`colour.offset_YCbCr`
- :func:`colour.RGB_to_YCbCr`
- :func:`colour.YCbCr_to_RGB`
- :func:`colour.RGB_to_YcCbcCrc`
- :func:`colour.YcCbcCrc_to_RGB`
Notes
-----
- *Y'CbCr* is not an absolute colourspace.
References
----------
- :cite:`InternationalTelecommunicationUnion2011e` : International
Telecommunication Union. (2011). Recommendation ITU-T T.871 - Information
technology - Digital compression and coding of continuous-tone still
images: JPEG File Interchange Format (JFIF).
https://www.itu.int/rec/dologin_pub.asp?lang=e&\
id=T-REC-T.871-201105-I!!PDF-E&type=items
- :cite:`InternationalTelecommunicationUnion2015h` : International
Telecommunication Union. (2015). Recommendation ITU-R BT.2020 - Parameter
values for ultra-high definition television systems for production and
international programme exchange (pp. 1-8).
https://www.itu.int/dms_pubrec/itu-r/rec/bt/\
R-REC-BT.2020-2-201510-I!!PDF-E.pdf
- :cite:`InternationalTelecommunicationUnion2015i` : International
Telecommunication Union. (2015). Recommendation ITU-R BT.709-6 - Parameter
values for the HDTV standards for production and international programme
exchange BT Series Broadcasting service (pp. 1-32).
https://www.itu.int/dms_pubrec/itu-r/rec/bt/\
R-REC-BT.709-6-201506-I!!PDF-E.pdf
- :cite:`InternationalTelecommunicationUnion2018` : International
Telecommunication Union. (2018). Recommendation ITU-R BT.2100-2 - Image
parameter values for high dynamic range television for use in production
and international programme exchange.
https://www.itu.int/dms_pubrec/itu-r/rec/bt/\
R-REC-BT.2100-2-201807-I!!PDF-E.pdf
- :cite:`SocietyofMotionPictureandTelevisionEngineers1999b` : Society of
Motion Picture and Television Engineers. (1999). ANSI/SMPTE 240M-1995 -
Signal Parameters - 1125-Line High-Definition Production Systems (pp. 1-7).
http://car.france3.mars.free.fr/HD/\
INA-%2026%20jan%2006/SMPTE%20normes%20et%20confs/s240m.pdf
- :cite:`Wikipedia2004d` : Wikipedia. (2004). YCbCr. Retrieved February 29,
2016, from https://en.wikipedia.org/wiki/YCbCr
"""
from __future__ import annotations
import typing
import numpy as np
if typing.TYPE_CHECKING:
from colour.hints import Any, ArrayLike, Domain1, NDArrayReal, Range1
from colour.hints import Annotated, NDArrayFloat, cast
from colour.models.rgb.transfer_functions import (
CV_range,
oetf_BT2020,
oetf_inverse_BT2020,
)
from colour.utilities import (
CanonicalMapping,
as_float_array,
as_int_array,
domain_range_scale,
from_range_1,
to_domain_1,
tsplit,
tstack,
)
__author__ = "Colour Developers"
__copyright__ = "Copyright 2013 Colour Developers"
__license__ = "BSD-3-Clause - https://opensource.org/licenses/BSD-3-Clause"
__maintainer__ = "Colour Developers"
__email__ = "colour-developers@colour-science.org"
__status__ = "Development"
__all__ = [
"WEIGHTS_YCBCR",
"SCALES_YCBCR",
"round_BT2100",
"ranges_YCbCr",
"matrix_YCbCr",
"offset_YCbCr",
"RGB_to_YCbCr",
"YCbCr_to_RGB",
"RGB_to_YcCbcCrc",
"YcCbcCrc_to_RGB",
]
WEIGHTS_YCBCR: CanonicalMapping = CanonicalMapping(
{
"ITU-R BT.601": np.array([0.2990, 0.1140]),
"ITU-R BT.709": np.array([0.2126, 0.0722]),
"ITU-R BT.2020": np.array([0.2627, 0.0593]),
"SMPTE-240M": np.array([0.2122, 0.0865]),
}
)
"""
Luma weightings presets.
References
----------
:cite:`InternationalTelecommunicationUnion2011e`,
:cite:`InternationalTelecommunicationUnion2015i`,
:cite:`InternationalTelecommunicationUnion2015h`,
:cite:`SocietyofMotionPictureandTelevisionEngineers1999b`,
:cite:`Wikipedia2004d`
"""
SCALES_YCBCR: CanonicalMapping = CanonicalMapping(
{
"Y'CbCr": np.array([0.5, 0.5]),
"Y'UV": np.array([0.436, 0.615]),
}
)
"""
Chroma scaling presets.
References
----------
:cite:`Wikipedia2004d`
"""
def round_BT2100(a: ArrayLike) -> NDArrayFloat:
"""
Round the specified array :math:`a` to the nearest integer using the
rounding method defined in *Recommendation ITU-R BT.2100*.
This function implements the specific rounding behaviour required by
*Recommendation ITU-R BT.2100*, where values are rounded to the nearest
integer with 0.5 rounding up.
Parameters
----------
a
Array :math:`a` to round.
Returns
-------
:class:`numpy.ndarray`
Rounded array :math:`a`.
References
----------
:cite:`InternationalTelecommunicationUnion2018`
Examples
--------
>>> round_BT2100(np.array([0.4, 0.5, 0.6]))
array([0., 1., 1.])
"""
return cast("NDArrayFloat", np.sign(a) * np.floor(np.abs(a) + 0.5))
def ranges_YCbCr(bits: int, is_legal: bool, is_int: bool) -> NDArrayFloat:
"""
Return the *Y'CbCr* colour encoding ranges array for the specified
bit-depth, range legality and representation.
Parameters
----------
bits
Bit-depth of the *Y'CbCr* colour encoding ranges array.
is_legal
Whether the *Y'CbCr* colour encoding ranges array is legal.
is_int
Whether the *Y'CbCr* colour encoding ranges array represents integer
code values.
Returns
-------
:class:`numpy.ndarray`
*Y'CbCr* colour encoding ranges array.
Examples
--------
>>> ranges_YCbCr(8, True, True)
array([ 16., 235., 16., 240.])
>>> ranges_YCbCr(8, True, False) # doctest: +ELLIPSIS
array([0.0627451..., 0.9215686..., 0.0627451..., 0.9411764...])
>>> ranges_YCbCr(10, False, False)
array([ 0. , 1. , -0.5, 0.5])
>>> ranges_YCbCr(10, False, True) # doctest: +ELLIPSIS
array([0.0000...e+00, 1.0230...e+03, 5.0000...e-01, 1.0235...e+03])
"""
if is_legal:
ranges = as_float_array([16, 235, 16, 240]) * 2 ** (bits - 8)
else:
ranges = as_float_array([0, 2**bits - 1, 0, 2**bits - 1])
if not is_int:
ranges = as_int_array(ranges) / (2**bits - 1)
if is_int and not is_legal:
ranges = as_float_array([ranges[0], ranges[1], 0.5, 2**bits - 0.5])
if not is_int and not is_legal:
ranges = as_float_array([ranges[0], ranges[1], -0.5, 0.5])
return ranges
[docs]
def matrix_YCbCr(
K: NDArrayFloat = WEIGHTS_YCBCR["ITU-R BT.709"],
S: NDArrayFloat = SCALES_YCBCR["Y'CbCr"],
bits: int = 8,
is_legal: bool = False,
is_int: bool = False,
) -> NDArrayFloat:
"""
Compute the *Y'CbCr* to *R'G'B'* matrix for the specified weights,
bit-depth, range legality and representation.
The related offset for the *R'G'B'* to *Y'CbCr* matrix can be computed
with the :func:`colour.offset_YCbCr` definition.
Parameters
----------
K
Luma weighting coefficients of red and blue. See
:attr:`colour.WEIGHTS_YCBCR` for presets. Default is
*(0.2126, 0.0722)*, the weightings for *ITU-R BT.709*.
S
Chroma scaling coefficients of *Cb* and *Cr*. See
:attr:`colour.SCALES_YCBCR` for presets. Default is
*(0.5, 0.5)*, the scaling for *Y'CbCr*.
bits
Bit-depth of the *Y'CbCr* colour encoding ranges array.
is_legal
Whether the *Y'CbCr* colour encoding ranges array is legal.
is_int
Whether the *Y'CbCr* colour encoding ranges array represents int
code values.
Returns
-------
:class:`numpy.ndarray`
*Y'CbCr* matrix.
Examples
--------
>>> matrix_YCbCr() # doctest: +ELLIPSIS
array([[ 1.0000000...e+00, ..., 1.5748000...e+00],
[ 1.0000000...e+00, -1.8732427...e-01, -4.6812427...e-01],
[ 1.0000000...e+00, 1.8556000...e+00, ...]])
>>> matrix_YCbCr(K=WEIGHTS_YCBCR["ITU-R BT.601"]) # doctest: +ELLIPSIS
array([[ 1.0000000...e+00, ..., 1.4020000...e+00],
[ 1.0000000...e+00, -3.4413628...e-01, -7.1413628...e-01],
[ 1.0000000...e+00, 1.7720000...e+00, ...]])
>>> matrix_YCbCr(is_legal=True) # doctest: +ELLIPSIS
array([[ 1.1643835...e+00, ..., 1.7927410...e+00],
[ 1.1643835...e+00, -2.1324861...e-01, -5.3290932...e-01],
[ 1.1643835...e+00, 2.1124017...e+00, ...]])
Computing the *Y'UV* to *R'G'B'* matrix:
>>> matrix_YCbCr(S=SCALES_YCBCR["Y'UV"]) # doctest: +ELLIPSIS
array([[ 1.0000000...e+00, ..., 1.2803252...e+00],
[ 1.0000000...e+00, -2.1482141...e-01, -3.8058884...e-01],
[ 1.0000000...e+00, 2.1279816...e+00, ...]])
Computing the *R'G'B'* to *Y'UV* matrix:
>>> np.linalg.inv(matrix_YCbCr(S=SCALES_YCBCR["Y'UV"]))
... # doctest: +ELLIPSIS
array([[ 0.2126... , 0.7152... , 0.0722... ],
[-0.0999068..., -0.3360931..., 0.436... ],
[ 0.615... , -0.5586080..., -0.0563919...]])
Matching the default output of the :func:`colour.RGB_to_YCbCr` is done as
follows:
>>> from colour.algebra import vecmul
>>> from colour.utilities import as_int_array
>>> RGB = np.array([1.0, 1.0, 1.0])
>>> RGB_to_YCbCr(RGB) # doctest: +ELLIPSIS
array([0.9215686..., 0.5019607..., 0.5019607...])
>>> YCbCr = vecmul(np.linalg.inv(matrix_YCbCr(is_legal=True)), RGB)
>>> YCbCr += offset_YCbCr(is_legal=True)
>>> YCbCr # doctest: +ELLIPSIS
array([0.9215686..., 0.5019607..., 0.5019607...])
Matching the int output of the :func:`colour.RGB_to_YCbCr` is done as
follows:
>>> RGB = np.array([102, 0, 51])
>>> RGB_to_YCbCr(RGB, in_bits=8, in_int=True, out_bits=8, out_int=True)
... # doctest: +SKIP
array([ 38, 140, 171])
>>> YCbCr = vecmul(np.linalg.inv(matrix_YCbCr(is_legal=True)), RGB)
>>> YCbCr += offset_YCbCr(is_legal=True, is_int=True)
>>> as_int_array(np.around(YCbCr))
... # doctest: +SKIP
array([ 38, 140, 171])
"""
Kr, Kb = K
Cb_scale, Cr_scale = S
Y_min, Y_max, C_min, C_max = ranges_YCbCr(bits, is_legal, is_int)
Y = np.array([Kr, (1 - Kr - Kb), Kb])
Cb = Cb_scale * (np.array([0, 0, 1]) - Y) / (1 - Kb)
Cr = Cr_scale * (np.array([1, 0, 0]) - Y) / (1 - Kr)
Y = Y * (Y_max - Y_min)
Cb = Cb * (C_max - C_min)
Cr = Cr * (C_max - C_min)
return np.linalg.inv(np.vstack([Y, Cb, Cr]))
[docs]
def offset_YCbCr(
bits: int = 8, is_legal: bool = False, is_int: bool = False
) -> NDArrayFloat:
"""
Compute the *R'G'B'* to *Y'CbCr* offsets for the specified bit-depth,
range legality and representation.
The related *R'G'B'* to *Y'CbCr* matrix can be computed with the
:func:`colour.matrix_YCbCr` definition.
Parameters
----------
bits
Bit-depth of the *Y'CbCr* colour encoding ranges array.
is_legal
Whether the *Y'CbCr* colour encoding ranges array is legal.
is_int
Whether the *Y'CbCr* colour encoding ranges array represents int
code values.
Returns
-------
:class:`numpy.ndarray`
*Y'CbCr* offsets.
Examples
--------
>>> offset_YCbCr()
array([0., 0., 0.])
>>> offset_YCbCr(is_legal=True) # doctest: +ELLIPSIS
array([0.0627451..., 0.5019607..., 0.5019607...])
"""
Y_min, _Y_max, C_min, C_max = ranges_YCbCr(bits, is_legal, is_int)
Y_offset = Y_min
C_offset = (C_min + C_max) / 2
return np.array([Y_offset, C_offset, C_offset])
[docs]
def RGB_to_YCbCr(
RGB: Domain1,
K: NDArrayFloat = WEIGHTS_YCBCR["ITU-R BT.709"],
S: NDArrayFloat = SCALES_YCBCR["Y'CbCr"],
in_bits: int = 10,
in_legal: bool = False,
in_int: bool = False,
out_bits: int = 8,
out_legal: bool = True,
out_int: bool = False,
clamp_int: bool = True,
**kwargs: Any,
) -> Annotated[NDArrayReal, 1]:
"""
Convert an array of *R'G'B'* values to the corresponding *Y'CbCr* colour
encoding values array.
Parameters
----------
RGB
Input *R'G'B'* array of floats or int values.
K
Luma weighting coefficients of red and blue. See
:attr:`colour.WEIGHTS_YCBCR` for presets. Default is
*(0.2126, 0.0722)*, the weightings for *ITU-R BT.709*.
S
Chroma scaling coefficients of *Cb* and *Cr*. See
:attr:`colour.SCALES_YCBCR` for presets. Default is
*(0.5, 0.5)*, the scaling for *Y'CbCr*.
in_bits
Bit-depth for int input, or used in the calculation of the
denominator for legal range float values, i.e., 8-bit means the
float value for legal white is *235 / 255*. Default is *10*.
in_legal
Whether to treat the input values as legal range. Default is
*False*.
in_int
Whether to treat the input values as ``in_bits`` int code values.
Default is *False*.
out_bits
Bit-depth for int output, or used in the calculation of the
denominator for legal range float values, i.e., 8-bit means the
float value for legal white is *235 / 255*. Ignored if
``out_legal`` and ``out_int`` are both *False*. Default is *8*.
out_legal
Whether to return legal range values. Default is *True*.
out_int
Whether to return values as ``out_bits`` int code values. Default
is *False*.
clamp_int
Whether to clamp int output to allowable range for ``out_bits``.
Default is *True*.
Other Parameters
----------------
in_range
Array overriding the computed range such as
*in_range = (RGB_min, RGB_max)*. If ``in_range`` is undefined,
*RGB_min* and *RGB_max* will be computed using
:func:`colour.CV_range` definition.
out_range
Array overriding the computed range such as
*out_range = (Y_min, Y_max, C_min, C_max)`. If ``out_range`` is
undefined, *Y_min*, *Y_max*, *C_min* and *C_max* will be computed
using :func:`colour.models.rgb.ycbcr.ranges_YCbCr` definition.
Returns
-------
:class:`numpy.ndarray`
*Y'CbCr* colour encoding array of int or float values.
Warnings
--------
For *Recommendation ITU-R BT.2020*,
:func:`colour.RGB_to_YCbCr` definition is only applicable to the
non-constant luminance implementation.
:func:`colour.RGB_to_YcCbcCrc` definition should be used for the
constant luminance case as per
:cite:`InternationalTelecommunicationUnion2015h`.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``RGB`` | 1 | 1 |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``YCbCr`` | 1 | 1 |
+------------+-----------------------+---------------+
- This definition has input and output int switches, thus the
domain-range scale information is only specified for the floating point
mode.
- The default arguments, ``**{'in_bits': 10, 'in_legal': False,
'in_int': False, 'out_bits': 8, 'out_legal': True, 'out_int':
False}`` transform a float *R'G'B'* input array normalised to
domain [0, 1] (``in_bits`` is ignored) to a float *Y'CbCr* output
array where *Y'* is normalised to range [16 / 255, 235 / 255] and
*Cb* and *Cr* are normalised to range [16 / 255, 240./255]. The
float values are calculated based on an [0, 255] int range, but no
8-bit quantisation or clamping are performed.
References
----------
:cite:`InternationalTelecommunicationUnion2011e`,
:cite:`InternationalTelecommunicationUnion2015i`,
:cite:`SocietyofMotionPictureandTelevisionEngineers1999b`,
:cite:`Wikipedia2004d`
Examples
--------
>>> RGB = np.array([1.0, 1.0, 1.0])
>>> RGB_to_YCbCr(RGB) # doctest: +ELLIPSIS
array([0.9215686..., 0.5019607..., 0.5019607...])
Matching the float output of *The Foundry Nuke*'s *Colorspace* node
set to *YCbCr*:
>>> RGB_to_YCbCr(RGB, out_range=(16 / 255, 235 / 255, 15.5 / 255, 239.5 / 255))
... # doctest: +ELLIPSIS
array([0.9215686..., 0.5 , 0.5 ])
Matching the float output of *The Foundry Nuke*'s *Colorspace* node
set to *YPbPr*:
>>> RGB_to_YCbCr(RGB, out_legal=False, out_int=False)
... # doctest: +ELLIPSIS
array([1., 0., 0.])
Computing *R'G'B'* to *Y'UV* values:
>>> RGB = np.array([0.75, 0.5, 0.25])
>>> RGB_to_YCbCr(RGB, S=SCALES_YCBCR["Y'UV"], out_legal=False, out_int=False)
... # doctest: +ELLIPSIS
array([ 0.5351..., -0.1339767..., 0.1678479...])
Creating int code values as per standard *10-bit SDI*:
>>> RGB = np.array([1.0, 1.0, 1.0])
>>> RGB_to_YCbCr(RGB, out_legal=True, out_bits=10, out_int=True)
... # doctest: +ELLIPSIS
array([940, 512, 512]...)
For *JFIF JPEG* conversion as per *Recommendation ITU-T T.871*
>>> RGB = np.array([102, 0, 51])
>>> RGB_to_YCbCr(
... RGB,
... K=WEIGHTS_YCBCR["ITU-R BT.601"],
... in_range=(0, 255),
... out_range=(0, 255, 0.5, 255.5),
... out_int=True,
... )
... # doctest: +ELLIPSIS
array([ 36, 136, 175]...)
Note the use of [0.5, 255.5] for the *Cb / Cr* range, which is
required so that the *Cb* and *Cr* output is centered about 128. Using
255 centres it about 127.5, meaning that there is no int code value to
represent achromatic colours. This does however create the possibility
of output int codes with value of 256, which cannot be stored in 8-bit
int representation. *Recommendation ITU-T T.871* specifies these should
be clamped to 255, which is applied with the default
``clamp_int=True``.
These *JFIF JPEG* ranges are also obtained as follows:
>>> RGB_to_YCbCr(
... RGB,
... K=WEIGHTS_YCBCR["ITU-R BT.601"],
... in_bits=8,
... in_int=True,
... out_legal=False,
... out_int=True,
... )
... # doctest: +ELLIPSIS
array([ 36, 136, 175]...)
"""
RGB = as_float_array(RGB) if in_int else to_domain_1(RGB)
Kr, Kb = K
Cb_scale, Cr_scale = S
RGB_min, RGB_max = kwargs.get("in_range", CV_range(in_bits, in_legal, in_int))
Y_min, Y_max, C_min, C_max = kwargs.get(
"out_range", ranges_YCbCr(out_bits, out_legal, out_int)
)
RGB_float = as_float_array(RGB) - RGB_min
RGB_float *= 1 / (RGB_max - RGB_min)
R, G, B = tsplit(RGB_float)
Y = Kr * R + (1 - Kr - Kb) * G + Kb * B
Cb = Cb_scale * (B - Y) / (1 - Kb)
Cr = Cr_scale * (R - Y) / (1 - Kr)
Y *= Y_max - Y_min
Y += Y_min
Cb *= C_max - C_min
Cr *= C_max - C_min
Cb += (C_max + C_min) / 2
Cr += (C_max + C_min) / 2
YCbCr = tstack([Y, Cb, Cr])
if out_int:
return as_int_array(
round_BT2100(np.clip(YCbCr, 0, 2**out_bits - 1) if clamp_int else YCbCr)
)
return from_range_1(YCbCr)
[docs]
def YCbCr_to_RGB(
YCbCr: Domain1,
K: NDArrayFloat = WEIGHTS_YCBCR["ITU-R BT.709"],
S: NDArrayFloat = SCALES_YCBCR["Y'CbCr"],
in_bits: int = 8,
in_legal: bool = True,
in_int: bool = False,
out_bits: int = 10,
out_legal: bool = False,
out_int: bool = False,
clamp_int: bool = True,
**kwargs: Any,
) -> Annotated[NDArrayReal, 1]:
"""
Convert an array of *Y'CbCr* colour encoding values to the
corresponding *R'G'B'* values array.
Parameters
----------
YCbCr
Input *Y'CbCr* colour encoding array of int or float values.
K
Luma weighting coefficients of red and blue. See
:attr:`colour.WEIGHTS_YCBCR` for presets. Default is
*(0.2126, 0.0722)*, the weightings for *ITU-R BT.709*.
S
Chroma scaling coefficients of *Cb* and *Cr*. See
:attr:`colour.SCALES_YCBCR` for presets. Default is
*(0.5, 0.5)*, the scaling for *Y'CbCr*.
in_bits
Bit-depth for int input, or used in the calculation of the
denominator for legal range float values, i.e., 8-bit means
the float value for legal white is *235 / 255*. Default is
*8*.
in_legal
Whether to treat the input values as legal range. Default is
*True*.
in_int
Whether to treat the input values as ``in_bits`` int code
values. Default is *False*.
out_bits
Bit-depth for int output, or used in the calculation of the
denominator for legal range float values, i.e., 8-bit means
the float value for legal white is *235 / 255*. Ignored if
``out_legal`` and ``out_int`` are both *False*. Default is
*10*.
out_legal
Whether to return legal range values. Default is *False*.
out_int
Whether to return values as ``out_bits`` int code values.
Default is *False*.
clamp_int
Whether to clamp int output to allowable range for
``out_bits``. Default is *True*.
Other Parameters
----------------
in_range
Array overriding the computed range such as
*in_range = (Y_min, Y_max, C_min, C_max)*. If ``in_range``
is undefined, *Y_min*, *Y_max*, *C_min* and *C_max* will be
computed using :func:`colour.models.rgb.ycbcr.ranges_YCbCr`
definition.
out_range
Array overriding the computed range such as
*out_range = (RGB_min, RGB_max)*. If ``out_range`` is
undefined, *RGB_min* and *RGB_max* will be computed using
:func:`colour.CV_range` definition.
Returns
-------
:class:`numpy.ndarray`
*R'G'B'* array of int or float values.
Notes
-----
+------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``YCbCr`` | 1 | 1 |
+------------+-----------------------+---------------+
+------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+============+=======================+===============+
| ``RGB`` | 1 | 1 |
+------------+-----------------------+---------------+
- This definition has input and output int switches, thus the
domain-range scale information is only specified for the floating point
mode.
Warnings
--------
For *Recommendation ITU-R BT.2020*,
:func:`colour.YCbCr_to_RGB` definition is only applicable to
the non-constant luminance implementation.
:func:`colour.YcCbcCrc_to_RGB` definition should be used for
the constant luminance case as per
:cite:`InternationalTelecommunicationUnion2015h`.
References
----------
:cite:`InternationalTelecommunicationUnion2011e`,
:cite:`InternationalTelecommunicationUnion2015i`,
:cite:`SocietyofMotionPictureandTelevisionEngineers1999b`,
:cite:`Wikipedia2004d`
Examples
--------
>>> YCbCr = np.array([502, 512, 512])
>>> YCbCr_to_RGB(YCbCr, in_bits=10, in_legal=True, in_int=True)
array([0.5, 0.5, 0.5])
Converting *Y'UV* values to *R'G'B'*:
>>> YUV = np.array([0.5351, -0.13397672, 0.16784798])
>>> YCbCr_to_RGB(YUV, S=SCALES_YCBCR["Y'UV"], in_legal=False, in_int=False)
... # doctest: +ELLIPSIS
array([0.75..., 0.5..., 0.25...])
"""
YCbCr = as_float_array(YCbCr) if in_int else to_domain_1(YCbCr)
Y, Cb, Cr = tsplit(YCbCr)
Kr, Kb = K
Cb_scale, Cr_scale = S
Y_min, Y_max, C_min, C_max = kwargs.get(
"in_range", ranges_YCbCr(in_bits, in_legal, in_int)
)
RGB_min, RGB_max = kwargs.get("out_range", CV_range(out_bits, out_legal, out_int))
Y = Y - Y_min
Cb = Cb - (C_max + C_min) / 2
Cr = Cr - (C_max + C_min) / 2
Y = Y * (1 / (Y_max - Y_min))
Cb = Cb * (1 / (C_max - C_min))
Cr = Cr * (1 / (C_max - C_min))
R = Y + (1 - Kr) / Cr_scale * Cr
B = Y + (1 - Kb) / Cb_scale * Cb
G = (Y - Kr * R - Kb * B) / (1 - Kr - Kb)
RGB = tstack([R, G, B])
RGB = RGB * (RGB_max - RGB_min) + RGB_min
return (
as_int_array(
round_BT2100(np.clip(RGB, 0, 2**out_bits - 1) if clamp_int else RGB)
)
if out_int
else from_range_1(RGB)
)
[docs]
def RGB_to_YcCbcCrc(
RGB: Domain1,
out_bits: int = 10,
out_legal: bool = True,
out_int: bool = False,
is_12_bits_system: bool = False,
**kwargs: Any,
) -> Annotated[NDArrayReal, 1]:
"""
Convert an array of *RGB* linear values to the corresponding *Yc'Cbc'Crc'*
colour encoding values array.
Parameters
----------
RGB
Input *RGB* array of linear float values.
out_bits
Bit-depth for int output, or used in the calculation of the
denominator for legal range float values, i.e., 8-bit means the float
value for legal white is *235 / 255*. Ignored if ``out_legal`` and
``out_int`` are both *False*. Default is *10*.
out_legal
Whether to return legal range values. Default is *True*.
out_int
Whether to return values as ``out_bits`` int code values. Default is
*False*.
is_12_bits_system
*Recommendation ITU-R BT.2020* OETF (OECF) adopts different parameters
for 10 and 12 bit systems. Default is *False*.
Other Parameters
----------------
out_range
Array overriding the computed range such as
*out_range = (Y_min, Y_max, C_min, C_max)*. If ``out_range`` is
undefined, *Y_min*, *Y_max*, *C_min* and *C_max* will be computed
using :func:`colour.models.rgb.ycbcr.ranges_YCbCr` definition.
Returns
-------
:class:`numpy.ndarray`
*Yc'Cbc'Crc'* colour encoding array of int or float values.
Notes
-----
+----------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+================+=======================+===============+
| ``RGB`` | 1 | 1 |
+----------------+-----------------------+---------------+
+----------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+================+=======================+===============+
| ``YcCbcCrc`` | 1 | 1 |
+----------------+-----------------------+---------------+
- This definition has input and output int switches, thus the
domain-range scale information is only specified for the floating point
mode.
Warnings
--------
This definition is specifically for usage with *Recommendation ITU-R
BT.2020* when adopting the constant luminance implementation.
References
----------
:cite:`InternationalTelecommunicationUnion2015h`, :cite:`Wikipedia2004d`
Examples
--------
>>> RGB = np.array([0.18, 0.18, 0.18])
>>> RGB_to_YcCbcCrc(
... RGB,
... out_legal=True,
... out_bits=10,
... out_int=True,
... is_12_bits_system=False,
... )
... # doctest: +ELLIPSIS
array([422, 512, 512]...)
"""
R, G, B = tsplit(to_domain_1(RGB))
Y_min, Y_max, C_min, C_max = kwargs.get(
"out_range", ranges_YCbCr(out_bits, out_legal, out_int)
)
Yc = 0.2627 * R + 0.6780 * G + 0.0593 * B
with domain_range_scale("ignore"):
Yc = oetf_BT2020(Yc, is_12_bits_system=is_12_bits_system)
R = oetf_BT2020(R, is_12_bits_system=is_12_bits_system)
B = oetf_BT2020(B, is_12_bits_system=is_12_bits_system)
Cbc = np.where((B - Yc) <= 0, (B - Yc) / 1.9404, (B - Yc) / 1.5816)
Crc = np.where((R - Yc) <= 0, (R - Yc) / 1.7184, (R - Yc) / 0.9936)
Yc = Yc * (Y_max - Y_min) + Y_min
Cbc = Cbc * (C_max - C_min) + (C_max + C_min) / 2
Crc = Crc * (C_max - C_min) + (C_max + C_min) / 2
YcCbcCrc = tstack([Yc, Cbc, Crc])
if out_int:
return as_int_array(np.round(YcCbcCrc))
return from_range_1(YcCbcCrc)
[docs]
def YcCbcCrc_to_RGB(
YcCbcCrc: Domain1,
in_bits: int = 10,
in_legal: bool = True,
in_int: bool = False,
is_12_bits_system: bool = False,
**kwargs: Any,
) -> Range1:
"""
Convert an array of *Yc'Cbc'Crc'* colour encoding values to the
corresponding *RGB* array of linear values.
Parameters
----------
YcCbcCrc
Input *Yc'Cbc'Crc'* colour encoding array of linear float values.
in_bits
Bit-depth for int input, or used in the calculation of the
denominator for legal range float values, i.e., 8-bit means the
float value for legal white is *235 / 255*. Default is *10*.
in_legal
Whether to treat the input values as legal range. Default is
*True*.
in_int
Whether to treat the input values as ``in_bits`` int code values.
Default is *False*.
is_12_bits_system
*Recommendation ITU-R BT.2020* EOTF (EOCF) adopts different
parameters for 10 and 12 bit systems. Default is *False*.
Other Parameters
----------------
in_range
Array overriding the computed range such as
*in_range = (Y_min, Y_max, C_min, C_max)*. If ``in_range`` is
undefined, *Y_min*, *Y_max*, *C_min* and *C_max* will be computed
using :func:`colour.models.rgb.ycbcr.ranges_YCbCr` definition.
Returns
-------
:class:`numpy.ndarray`
*RGB* array of linear float values.
Notes
-----
+----------------+-----------------------+---------------+
| **Domain** | **Scale - Reference** | **Scale - 1** |
+================+=======================+===============+
| ``YcCbcCrc`` | 1 | 1 |
+----------------+-----------------------+---------------+
+----------------+-----------------------+---------------+
| **Range** | **Scale - Reference** | **Scale - 1** |
+================+=======================+===============+
| ``RGB`` | 1 | 1 |
+----------------+-----------------------+---------------+
- This definition has input and output int switches, thus the
domain-range scale information is only specified for the floating point
mode.
Warnings
--------
This definition is specifically for usage with
*Recommendation ITU-R BT.2020* when adopting the constant luminance
implementation.
References
----------
:cite:`InternationalTelecommunicationUnion2015h`,
:cite:`Wikipedia2004d`
Examples
--------
>>> YcCbcCrc = np.array([1689, 2048, 2048])
>>> YcCbcCrc_to_RGB(
... YcCbcCrc,
... in_legal=True,
... in_bits=12,
... in_int=True,
... is_12_bits_system=True,
... )
... # doctest: +ELLIPSIS
array([0.1800903..., 0.1800903..., 0.1800903...])
"""
YcCbcCrc = as_float_array(YcCbcCrc) if in_int else to_domain_1(YcCbcCrc)
Yc, Cbc, Crc = tsplit(YcCbcCrc)
Y_min, Y_max, C_min, C_max = kwargs.get(
"in_range", ranges_YCbCr(in_bits, in_legal, in_int)
)
Yc = (Yc - Y_min) * (1 / (Y_max - Y_min))
Cbc = (Cbc - (C_max + C_min) / 2) * (1 / (C_max - C_min))
Crc = (Crc - (C_max + C_min) / 2) * (1 / (C_max - C_min))
B = np.where(Cbc <= 0, Cbc * 1.9404 + Yc, Cbc * 1.5816 + Yc)
R = np.where(Crc <= 0, Crc * 1.7184 + Yc, Crc * 0.9936 + Yc)
with domain_range_scale("ignore"):
Yc = oetf_inverse_BT2020(Yc, is_12_bits_system)
B = oetf_inverse_BT2020(B, is_12_bits_system)
R = oetf_inverse_BT2020(R, is_12_bits_system)
G = (Yc - 0.0593 * B - 0.2627 * R) / 0.6780
RGB = tstack([R, G, B])
return from_range_1(RGB)
