#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
DICOM - Grayscale Standard Display Function
===========================================
Defines the *DICOM - Grayscale Standard Display Function* opto-electrical
transfer function (OETF / OECF) and electro-optical transfer function
(EOTF / EOCF):
- :func:`oetf_DICOMGSDF`
- :func:`eotf_DICOMGSDF`
The Grayscale Standard Display Function is defined for the Luminance Range
from :math:`0.05` to :math:`4000 cd/m^2`. The minimum Luminance corresponds
to the lowest practically useful Luminance of cathode-ray-tube (CRT) monitors
and the maximum exceeds the unattenuated Luminance of very bright light-boxes
used for interpreting X-Ray mammography. The Grayscale Standard Display
Function explicitly includes the effects of the diffused ambient Illuminance.
See Also
--------
`RGB Colourspaces Jupyter Notebook
<http://nbviewer.jupyter.org/github/colour-science/colour-notebooks/\
blob/master/notebooks/models/rgb.ipynb>`_
References
----------
.. [1] National Electrical Manufacturers Association. (2004). Digital Imaging
and Communications in Medicine ( DICOM ) Part 14 :
Grayscale Standard Display Function. Medicine, 10(S1), 3–4.
doi:10.1007/BF03168637
"""
from __future__ import division, unicode_literals
import numpy as np
from colour.utilities import Structure, as_numeric
__author__ = 'Colour Developers'
__copyright__ = 'Copyright (C) 2013-2017 - Colour Developers'
__license__ = 'New BSD License - http://opensource.org/licenses/BSD-3-Clause'
__maintainer__ = 'Colour Developers'
__email__ = 'colour-science@googlegroups.com'
__status__ = 'Production'
__all__ = ['DICOMGSDF_CONSTANTS', 'oetf_DICOMGSDF', 'eotf_DICOMGSDF']
DICOMGSDF_CONSTANTS = Structure(
a=-1.3011877,
b=-2.5840191e-2,
c=8.0242636e-2,
d=-1.0320229e-1,
e=1.3646699e-1,
f=2.8745620e-2,
g=-2.5468404e-2,
h=-3.1978977e-3,
k=1.2992634e-4,
m=1.3635334e-3,
A=71.498068,
B=94.593053,
C=41.912053,
D=9.8247004,
E=0.28175407,
F=-1.1878455,
G=-0.18014349,
H=0.14710899,
I=-0.017046845)
"""
*DICOM Grayscale Standard Display Function* constants.
DICOMGSDF_CONSTANTS : Structure
"""
[docs]def oetf_DICOMGSDF(L):
"""
Defines the *DICOM - Grayscale Standard Display Function* opto-electronic
transfer function (OETF / OECF).
Parameters
----------
L : numeric or array_like
*Luminance* :math:`L`.
Returns
-------
numeric or ndarray
Just-Noticeable Difference (JND) Index, :math:`j` in domain 1 to 1023.
Examples
--------
>>> oetf_DICOMGSDF(130.065284012159790) # doctest: +ELLIPSIS
511.9964806...
"""
L = np.asarray(L)
L_lg = np.log10(L)
A = DICOMGSDF_CONSTANTS.A
B = DICOMGSDF_CONSTANTS.B
C = DICOMGSDF_CONSTANTS.C
D = DICOMGSDF_CONSTANTS.D
E = DICOMGSDF_CONSTANTS.E
F = DICOMGSDF_CONSTANTS.F
G = DICOMGSDF_CONSTANTS.G
H = DICOMGSDF_CONSTANTS.H
I = DICOMGSDF_CONSTANTS.I
L = (A + B * L_lg + C * L_lg ** 2 + D * L_lg ** 3 + E * L_lg ** 4 +
F * L_lg ** 5 + G * L_lg ** 6 + H * L_lg ** 7 + I * L_lg ** 8)
return as_numeric(L)
[docs]def eotf_DICOMGSDF(J):
"""
Defines the *DICOM - Grayscale Standard Display Function* electro-optical
transfer function (EOTF / EOCF).
Parameters
----------
J : numeric or array_like
Just-Noticeable Difference (JND) Index, :math:`j` in range 1 to 1023.
Returns
-------
numeric or ndarray
Corresponding *luminance* :math:`L`.
Examples
--------
>>> eotf_DICOMGSDF(512) # doctest: +ELLIPSIS
130.0652840...
"""
J = np.asarray(J)
a = DICOMGSDF_CONSTANTS.a
b = DICOMGSDF_CONSTANTS.b
c = DICOMGSDF_CONSTANTS.c
d = DICOMGSDF_CONSTANTS.d
e = DICOMGSDF_CONSTANTS.e
f = DICOMGSDF_CONSTANTS.f
g = DICOMGSDF_CONSTANTS.g
h = DICOMGSDF_CONSTANTS.h
k = DICOMGSDF_CONSTANTS.k
m = DICOMGSDF_CONSTANTS.m
J_ln = np.log(J)
J_ln2 = J_ln ** 2
J_ln3 = J_ln ** 3
J_ln4 = J_ln ** 4
J_ln5 = J_ln ** 5
L = ((a + c * J_ln + e * J_ln2 + g * J_ln3 + m * J_ln4) /
(1 + b * J_ln + d * J_ln2 + f * J_ln3 + h * J_ln4 + k * J_ln5))
L = 10 ** L
return as_numeric(L)