mirror of
https://github.com/wassname/scikit-image.git
synced 2026-07-17 11:32:45 +08:00
Added support for different illuminants.
This commit is contained in:
capitanbatata
+5
-5
@@ -65,11 +65,11 @@ from skimage._shared.utils import deprecated as _deprecated
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pkg_dir = _osp.abspath(_osp.dirname(__file__))
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data_dir = _osp.join(pkg_dir, 'data')
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try:
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from .version import version as __version__
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except ImportError:
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__version__ = "unbuilt-dev"
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del version
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# try:
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# from .version import version as __version__
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# except ImportError:
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# __version__ = "unbuilt-dev"
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# del version
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try:
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+139
-24
@@ -322,8 +322,86 @@ gray_from_rgb = np.array([[0.2125, 0.7154, 0.0721],
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[0, 0, 0]])
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# CIE LAB constants for Observer= 2A, Illuminant= D65
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## NOTE: this is actually the XYZ values for the illuminant above.
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lab_ref_white = np.array([0.95047, 1., 1.08883])
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## XYZ coordinates of the illuminants, scaled to [0, 1]. For each illuminant I we have:
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##
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## illuminant[I][0] corresponds to the XYZ coordinates for the 2 degree
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## field of view.
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##
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## illuminant[I][1] corresponds to the XYZ coordinates for the 10 degree
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## field of view.
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##
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## The XYZ coordinates are calculated from [1], using the formula:
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##
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## X = x * ( Y / y )
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## Y = Y
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## Z = ( 1 - x - y ) * ( Y / y )
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##
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## where Y = 1. The only exception is the illuminant "D65" with aperture angle
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## 2, whose coordinates are copied from 'lab_ref_white' for
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## backward-compatibility reasons.
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##
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## References
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## ----------
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## .. [1] http://en.wikipedia.org/wiki/Standard_illuminant
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illuminants = \
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{"A": [[1.098466069456375, 1, 0.3558228003436005], \
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[1.111420406956693, 1, 0.3519978321919493]], \
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"D50": [[0.9642119944211994, 1, 0.8251882845188288], \
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[0.9672062750333777, 1, 0.8142801513128616]], \
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"D55": [[0.956797052643698, 1, 0.9214805860173273], \
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[0.9579665682254781, 1, 0.9092525159847462]], \
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"D65": [lab_ref_white, \
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[0.94809667673716, 1, 1.0730513595166162]], \
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"D75": [[0.9497220898840717, 1, 1.226393520724154], \
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[0.9441713925645873, 1, 1.2064272211720228]], \
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"E": [[1.0, 1.0, 1.0], \
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[1.0, 1.0, 1.0]]
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}
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def get_xyz_coords(illuminant, observer):
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"""Get the XYZ coordinates of the given illuminant and observer [1]. Currently
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supported illuminants are: "A", "D50", "D55", "D65", "D75", "E".
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Parameters
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----------
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illuminant: string
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The name of the illuminant (the function is NOT case sensitive).
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observer: int
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The aperture angle of the observer.
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Returns
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-------
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xyz_coords: list
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A list with 3 elements containing the XYZ coordinates of the given
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illuminant.
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Raises
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------
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ValueError
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If either the illuminant or the observer angle are not supported or
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unknown.
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References
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----------
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.. [1] http://en.wikipedia.org/wiki/Standard_illuminant
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"""
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illuminant = illuminant.upper()
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if illuminant in illuminants.keys():
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if observer == 2:
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idx = 0
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elif observer == 10:
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idx = 10
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else:
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ValueError("Unknown observer \"{}\"".format(observer))
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return illuminants[illuminant][idx]
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else:
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ValueError("Unknown illuminant \"{}\"".format(illuminant))
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# Haematoxylin-Eosin-DAB colorspace
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# From original Ruifrok's paper: A. C. Ruifrok and D. A. Johnston,
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@@ -666,9 +744,8 @@ def gray2rgb(image):
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return np.concatenate(3 * (image,), axis=-1)
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else:
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raise ValueError("Input image expected to be RGB, RGBA or gray.")
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def xyz2lab(xyz):
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def xyz2lab(xyz, illuminant = "D65", observer = 2999999999):
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"""XYZ to CIE-LAB color space conversion.
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Parameters
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@@ -676,6 +753,10 @@ def xyz2lab(xyz):
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xyz : array_like
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The image in XYZ format, in a 3- or 4-D array of shape
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``(.., ..,[ ..,] 3)``.
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illuminant: string
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The name of the illuminant (the function is NOT case sensitive).
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observer: int
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The aperture angle of the observer.
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Returns
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-------
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@@ -687,11 +768,15 @@ def xyz2lab(xyz):
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------
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ValueError
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If `xyz` is not a 3-D array of shape ``(.., ..,[ ..,] 3)``.
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ValueError
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If either the illuminant or the observer angle are not supported or
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unknown.
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Notes
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-----
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Observer= 2A, Illuminant= D65
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CIE XYZ tristimulus values x_ref = 95.047, y_ref = 100., z_ref = 108.883
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By default Observer= 2A, Illuminant= D65. CIE XYZ tristimulus values x_ref
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= 95.047, y_ref = 100., z_ref = 108.883. See function 'get_xyz_coords' for
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a list of supported illuminants.
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References
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----------
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@@ -705,11 +790,14 @@ def xyz2lab(xyz):
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>>> lena = data.lena()
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>>> lena_xyz = rgb2xyz(lena)
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>>> lena_lab = xyz2lab(lena_xyz)
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"""
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arr = _prepare_colorarray(xyz)
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xyz_ref_white = get_xyz_coords(illuminant, observer)
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# scale by CIE XYZ tristimulus values of the reference white point
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arr = arr / lab_ref_white
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arr = arr / xyz_ref_white
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# Nonlinear distortion and linear transformation
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mask = arr > 0.008856
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@@ -725,14 +813,17 @@ def xyz2lab(xyz):
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return np.concatenate([x[..., np.newaxis] for x in [L, a, b]], axis=-1)
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def lab2xyz(lab):
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def lab2xyz(lab, illuminant = "D65", observer = 2):
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"""CIE-LAB to XYZcolor space conversion.
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Parameters
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----------
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lab : array_like
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The image in lab format, in a 3-D array of shape ``(.., .., 3)``.
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illuminant: string
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The name of the illuminant (the function is NOT case sensitive).
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observer: int
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The aperture angle of the observer.
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Returns
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-------
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@@ -743,11 +834,16 @@ def lab2xyz(lab):
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------
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ValueError
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If `lab` is not a 3-D array of shape ``(.., .., 3)``.
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ValueError
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If either the illuminant or the observer angle are not supported or
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unknown.
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Notes
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-----
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Observer = 2A, Illuminant = D65
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CIE XYZ tristimulus values x_ref = 95.047, y_ref = 100., z_ref = 108.883
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By default Observer= 2A, Illuminant= D65. CIE XYZ tristimulus values x_ref
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= 95.047, y_ref = 100., z_ref = 108.883. See function 'get_xyz_coords' for
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a list of supported illuminants.
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References
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----------
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@@ -769,11 +865,11 @@ def lab2xyz(lab):
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out[mask] = np.power(out[mask], 3.)
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out[~mask] = (out[~mask] - 16.0 / 116.) / 7.787
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# rescale Observer= 2 deg, Illuminant= D65
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out *= lab_ref_white
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# rescale to the reference white (illuminant)
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xyz_ref_white = get_xyz_coords(illuminant, observer)
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out *= xyz_ref_white
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return out
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def rgb2lab(rgb):
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"""RGB to lab color space conversion.
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@@ -826,7 +922,7 @@ def lab2rgb(lab):
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return xyz2rgb(lab2xyz(lab))
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def xyz2luv(xyz):
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def xyz2luv(xyz, illuminant = "D65", observer = 2):
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"""XYZ to CIE-Luv color space conversion.
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Parameters
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@@ -834,6 +930,10 @@ def xyz2luv(xyz):
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xyz : (M, N, [P,] 3) array_like
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The 3 or 4 dimensional image in XYZ format. Final dimension denotes
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channels.
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illuminant: string
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The name of the illuminant (the function is NOT case sensitive).
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observer: int
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The aperture angle of the observer.
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Returns
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-------
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@@ -844,11 +944,16 @@ def xyz2luv(xyz):
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------
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ValueError
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If `xyz` is not a 3-D or 4-D array of shape ``(M, N, [P,] 3)``.
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ValueError
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If either the illuminant or the observer angle are not supported or
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unknown.
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Notes
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-----
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XYZ conversion weights use Observer = 2A. Reference whitepoint for D65
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Illuminant, with XYZ tristimulus values of ``(95.047, 100., 108.883)``.
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By default XYZ conversion weights use Observer = 2A. Reference whitepoint
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for D65 Illuminant, with XYZ tristimulus values of ``(95.047, 100.,
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108.883)``. See function 'get_xyz_coords' for a list of supported
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illuminants.
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References
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----------
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@@ -871,13 +976,14 @@ def xyz2luv(xyz):
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eps = np.finfo(np.float).eps
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# compute y_r and L
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L = y / lab_ref_white[1]
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xyz_ref_white = get_xyz_coords(illuminant, observer)
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L = y / xyz_ref_white[1]
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mask = L > 0.008856
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L[mask] = 116. * np.power(L[mask], 1. / 3.) - 16.
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L[~mask] = 903.3 * L[~mask]
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u0 = 4*lab_ref_white[0] / np.dot([1, 15, 3], lab_ref_white)
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v0 = 9*lab_ref_white[1] / np.dot([1, 15, 3], lab_ref_white)
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u0 = 4*xyz_ref_white[0] / np.dot([1, 15, 3], xyz_ref_white)
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v0 = 9*xyz_ref_white[1] / np.dot([1, 15, 3], xyz_ref_white)
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# u' and v' helper functions
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def fu(X, Y, Z):
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@@ -893,7 +999,7 @@ def xyz2luv(xyz):
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return np.concatenate([q[..., np.newaxis] for q in [L, u, v]], axis=-1)
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def luv2xyz(luv):
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def luv2xyz(luv, illuminant = "D65", observer = 2):
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"""CIE-Luv to XYZ color space conversion.
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Parameters
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@@ -901,6 +1007,10 @@ def luv2xyz(luv):
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luv : (M, N, [P,] 3) array_like
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The 3 or 4 dimensional image in CIE-Luv format. Final dimension denotes
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channels.
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illuminant: string
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The name of the illuminant (the function is NOT case sensitive).
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observer: int
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The aperture angle of the observer.
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Returns
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-------
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@@ -911,11 +1021,15 @@ def luv2xyz(luv):
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------
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ValueError
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If `luv` is not a 3-D or 4-D array of shape ``(M, N, [P,] 3)``.
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ValueError
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If either the illuminant or the observer angle are not supported or
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unknown.
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Notes
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-----
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XYZ conversion weights use Observer = 2A. Reference whitepoint for D65
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Illuminant, with XYZ tristimulus values of ``(95.047, 100., 108.883)``.
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Illuminant, with XYZ tristimulus values of ``(95.047, 100., 108.883)``. See
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function 'get_xyz_coords' for a list of supported illuminants.
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References
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----------
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@@ -935,12 +1049,13 @@ def luv2xyz(luv):
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mask = y > 7.999625
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y[mask] = np.power((y[mask]+16.) / 116., 3.)
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y[~mask] = y[~mask] / 903.3
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y *= lab_ref_white[1]
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xyz_ref_white = get_xyz_coords(illuminant, observer)
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y *= xyz_ref_white[1]
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# reference white x,z
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uv_weights = [1, 15, 3]
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u0 = 4*lab_ref_white[0] / np.dot(uv_weights, lab_ref_white)
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v0 = 9*lab_ref_white[1] / np.dot(uv_weights, lab_ref_white)
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u0 = 4*xyz_ref_white[0] / np.dot(uv_weights, xyz_ref_white)
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v0 = 9*xyz_ref_white[1] / np.dot(uv_weights, xyz_ref_white)
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# compute intermediate values
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a = u0 + u / (13.*L + eps)
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