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Add colorspaces: YUV, YIQ, YPbPr, YCbCr

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This commit is contained in:
Alex Izvorski
2016-04-30 00:58:34 -07:00
parent a406e270b1
commit 8dc4d3509e
1 changed files with 222 additions and 2 deletions
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skimage/color/colorconv.py
+222 -2
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@@ -124,9 +124,9 @@ def convert_colorspace(arr, fromspace, tospace):
>>> img_hsv = convert_colorspace(img, 'RGB', 'HSV')
"""
fromdict = {'RGB': lambda im: im, 'HSV': hsv2rgb, 'RGB CIE': rgbcie2rgb,
'XYZ': xyz2rgb}
'XYZ': xyz2rgb, 'YUV': yuv2rgb, 'YIQ': yiq2rgb, 'YPbPr': ypbpr2rgb, 'YCbCr': ycbcr2rgb }
todict = {'RGB': lambda im: im, 'HSV': rgb2hsv, 'RGB CIE': rgb2rgbcie,
'XYZ': rgb2xyz}
'XYZ': rgb2xyz, 'YUV': rgb2yuv, 'YIQ': rgb2yiq, 'YPbPr': rgb2ypbpr, 'YCbCr': rgb2ycbcr }
fromspace = fromspace.upper()
tospace = tospace.upper()
@@ -322,6 +322,30 @@ gray_from_rgb = np.array([[0.2125, 0.7154, 0.0721],
[0, 0, 0],
[0, 0, 0]])
yuv_from_rgb = np.array([[ 0.299 , 0.587 , 0.114 ],
[-0.14714119, -0.28886916, 0.43601035 ],
[ 0.61497538, -0.51496512, -0.10001026 ]]).T
rgb_from_yuv = linalg.inv(yuv_from_rgb)
yiq_from_rgb = np.array([[0.299 , 0.587 , 0.114 ],
[0.59590059, -0.27455667, -0.32134392],
[0.21153661, -0.52273617, 0.31119955]]).T
rgb_from_yiq = linalg.inv(yiq_from_rgb)
ypbpr_from_rgb = np.array([[ 0.299 , 0.587 , 0.114 ],
[-0.168736,-0.331264, 0.5 ],
[ 0.5 ,-0.418688,-0.081312]]).T
rgb_from_ypbpr = linalg.inv(ypbpr_from_rgb)
ycbcr_from_rgb = np.array([[ 65.481, 128.553, 24.966],
[ -37.797, -74.203, 112.0 ],
[ 112.0 , -93.786, -18.214]]).T
rgb_from_ycbcr = linalg.inv(ycbcr_from_rgb)
# CIE LAB constants for Observer=2A, Illuminant=D65
# NOTE: this is actually the XYZ values for the illuminant above.
lab_ref_white = np.array([0.95047, 1., 1.08883])
@@ -1456,3 +1480,199 @@ def _prepare_lab_array(arr):
if shape[-1] < 3:
raise ValueError('Input array has less than 3 color channels')
return dtype.img_as_float(arr, force_copy=True)
def rgb2yuv(rgb):
"""RGB to YUV color space conversion.
Parameters
----------
rgb : array_like
The image in RGB format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Returns
-------
out : ndarray
The image in YUV format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Raises
------
ValueError
If `rgb` is not a 3- or 4-D array of shape ``(.., ..,[ ..,] 3)``.
Notes
-----
Y is between 0 and 1. Use YCbCr instead of YUV for the color space which is commonly used by video codecs (where Y ranges from 16 to 235)
"""
return _convert(yuv_from_rgb, rgb)
def rgb2yiq(rgb):
"""RGB to YIQ color space conversion.
Parameters
----------
rgb : array_like
The image in RGB format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Returns
-------
out : ndarray
The image in YIQ format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Raises
------
ValueError
If `rgb` is not a 3- or 4-D array of shape ``(.., ..,[ ..,] 3)``.
"""
return _convert(yiq_from_rgb, rgb)
def rgb2ypbpr(rgb):
"""RGB to YIQ color space conversion.
Parameters
----------
rgb : array_like
The image in RGB format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Returns
-------
out : ndarray
The image in YIQ format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Raises
------
ValueError
If `rgb` is not a 3- or 4-D array of shape ``(.., ..,[ ..,] 3)``.
"""
return _convert(ypbpr_from_rgb, rgb)
def rgb2ycbcr(rgb):
"""RGB to YCbCr color space conversion.
Parameters
----------
rgb : array_like
The image in RGB format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Returns
-------
out : ndarray
The image in YCbCr format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Raises
------
ValueError
If `rgb` is not a 3- or 4-D array of shape ``(.., ..,[ ..,] 3)``.
Notes
-----
The destination color space is sometimes also called "YUV"
"""
arr = _convert(ycbcr_from_rgb, rgb)
arr[..., 0] += 16
arr[..., 1] += 128
arr[..., 2] += 128
return arr
def yuv2rgb(yuv):
"""RGB to YIQ color space conversion.
Parameters
----------
rgb : array_like
The image in RGB format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Returns
-------
out : ndarray
The image in YIQ format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Raises
------
ValueError
If `rgb` is not a 3- or 4-D array of shape ``(.., ..,[ ..,] 3)``.
"""
return _convert(rgb_from_yuv, yuv)
def yiq2rgb(yiq):
"""YIQ to RGB color space conversion.
Parameters
----------
yiq : array_like
The image in YIQ format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Returns
-------
out : ndarray
The image in RGB format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Raises
------
ValueError
If `yiq` is not a 3- or 4-D array of shape ``(.., ..,[ ..,] 3)``.
"""
return _convert(rgb_from_yiq, yiq)
def ypbpr2rgb(ypbpr):
"""YPbPr to RGB color space conversion.
Parameters
----------
ypbpr : array_like
The image in YPbPr format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Returns
-------
out : ndarray
The image in RGB format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Raises
------
ValueError
If `ypbpr` is not a 3- or 4-D array of shape ``(.., ..,[ ..,] 3)``.
"""
return _convert(rgb_from_ypbpr, ypbpr)
def ycbcr2rgb(ycbcr):
"""YCbCr to RGB color space conversion.
Parameters
----------
ycbcr : array_like
The image in YCbCr format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Returns
-------
out : ndarray
The image in RGB format, in a 3- or 4-D array of shape
``(.., ..,[ ..,] 3)``.
Raises
------
ValueError
If `ycbcr` is not a 3- or 4-D array of shape ``(.., ..,[ ..,] 3)``.
Notes
-----
The source color space is sometimes also called "YUV"
"""
arr = ycbcr.copy()
arr[..., 0] -= 16
arr[..., 1] -= 128
arr[..., 2] -= 128
return _convert(rgb_from_ycbcr, arr)