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InvertAgXBaseRec2020.py
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InvertAgXBaseRec2020.py
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import colour
import numpy
# Log range parameters
midgrey = 0.18
normalized_log2_minimum = -10
normalized_log2_maximum = +6.5
# define color space matrices
inset_matrix = numpy.array([[0.856627153315983, 0.0951212405381588, 0.0482516061458583],
[0.137318972929847, 0.761241990602591, 0.101439036467562],
[0.11189821299995, 0.0767994186031903, 0.811302368396859]])
outset_matrix = numpy.linalg.inv(numpy.array([[0.899796955911611, 0.0871996192028351, 0.013003424885555],
[0.11142098895748, 0.875575586156966, 0.0130034248855548],
[0.11142098895748, 0.0871996192028349, 0.801379391839686]]))
default_contrast = colour.io.read_LUT_SonySPI1D('AgX_Default_Contrast.spi1d')
inverse = default_contrast.invert(extrapolate=True, interpolator='Tetrahedral')
def apply_inverse_sigmoid(x):
col = inverse.apply(x)
return col
colour.utilities.filter_warnings(python_warnings=True)
def main():
# resolution of the 3DLUT
LUT_res = 36
mix_percent = 40
LUT = colour.LUT3D(name=f'Inverse AgX_Formation Rec.2020',
size=LUT_res)
LUT.domain = ([[0.0, 0.0, 0.0], [1.0, 1.0, 1.0]])
LUT.comments = [f'Inverse of AgX Base Rec.2020 Formation LUT',
f'This LUT expects input to be Rec.2020 power 2.4, output to be Rec.2020 Log2 from -10 stops to +6.5 stops']
x, y, z, _ = LUT.table.shape
for i in range(x):
for j in range(y):
for k in range(z):
col = numpy.array(LUT.table[i][j][k], dtype=numpy.longdouble)
# decode Rec.2020 image's power 2.4 transfer function
col = colour.models.exponent_function_basic(col, 2.4, 'basicFwd')
# inverse the outset matrix
col = numpy.tensordot(col, numpy.linalg.inv(outset_matrix), axes=(0, 1))
# re-encode transfer function
col = colour.models.exponent_function_basic(col, 2.4, 'basicRev')
# record formed image's chroma angle
formed_hsv = colour.RGB_to_HSV(col)
# inverse sigmoid
col = apply_inverse_sigmoid(col)
# decode Log2 curve
col = colour.log_decoding(col,
function='Log2',
min_exposure=-10,
max_exposure=+6.5,
middle_grey=midgrey)
# re-encode transfer function
col = colour.models.exponent_function_basic(col, 2.4, 'basicRev')
# record inverted result's chroma angle
inverted_hsv = colour.RGB_to_HSV(col)
# mix pre-invert and post-invert chroma angle
inverted_hsv[0] = colour.algebra.lerp(mix_percent/100, formed_hsv[0], inverted_hsv[0], False)
col = colour.HSV_to_RGB(inverted_hsv)
# decode power 2.4 transfer function
col = colour.models.exponent_function_basic(col, 2.4, 'basicFwd')
# invert the inset matrix
col = numpy.tensordot(col, numpy.linalg.inv(inset_matrix), axes=(0, 1))
# re-encode log2 curve
col = colour.log_encoding(col,
function='Log2',
min_exposure=-10,
max_exposure=+6.5,
middle_grey=midgrey)
LUT.table[i][j][k] = numpy.array(col, dtype=LUT.table.dtype)
colour.write_LUT(
LUT,
f"Inverse_AgX_Base_Rec2020.cube")
print(LUT)
if __name__ == '__main__':
try:
main()
except KeyboardInterrupt:
pass