def test_rgb_to_lab_to_rgb(self):
np.random.seed(1)
im_rand = np.random.randint(0, 255, (10, 10, 3))
np.testing.assert_array_almost_equal(
np.round(lab_to_rgb(rgb_to_lab(im_rand))), im_rand)
def test_rgb_to_lab_to_rgb(self):
np.random.seed(1)
im_rand = np.random.randint(0, 255, (10, 10, 3))
np.testing.assert_array_almost_equal(
np.round(lab_to_rgb(rgb_to_lab(im_rand))),
im_rand
)
def reinhard(im_src,
target_mu,
target_sigma,
src_mu=None,
src_sigma=None,
mask_out=None):
"""Perform Reinhard color normalization.
Transform the color characteristics of an image to a desired standard.
The standard is defined by the mean and standard deviations of the target
image in LAB color space defined by Ruderman. The input image is converted
to Ruderman's LAB space, the LAB channels are each centered and scaled to
zero-mean unit variance, and then rescaled and shifted to match the target
image statistics. If the LAB statistics for the input image are provided
(`src_mu` and `src_sigma`) then these will be used for normalization,
otherwise they will be derived from the input image `im_src`.
Parameters
----------
im_src : array_like
An RGB image
target_mu : array_like
A 3-element array containing the means of the target image channels
in LAB color space.
target_sigma : array_like
A 3-element array containing the standard deviations of the target
image channels in LAB color space.
src_mu : array_like, optional
A 3-element array containing the means of the source image channels in
LAB color space. Used with reinhard_stats for uniform normalization of
tiles from a slide.
src_sigma : array, optional
A 3-element array containing the standard deviations of the source
image channels in LAB color space. Used with reinhard_stats for
uniform normalization of tiles tiles from a slide.
mask_out : array_like, default is None
if not None, should be (m, n) boolean numpy array.
This method uses numpy masked array functionality to only use
non-masked areas in calculations. This is relevant because elements
like blood, sharpie marker, white space, etc would throw off the
reinhard normalization by affecting the mean and stdev. Ideally, you
want to exclude these elements from both the target image (from which
you calculate target_mu and target_sigma) and from the source image
to be normalized.
Returns
-------
im_normalized : array_like
Color Normalized RGB image
See Also
--------
histomicstk.preprocessing.color_conversion.rgb_to_lab,
histomicstk.preprocessing.color_conversion.lab_to_rgb
References
----------
.. [#] E. Reinhard, M. Adhikhmin, B. Gooch, P. Shirley, "Color transfer
between images," in IEEE Computer Graphics and Applications, vol.21,
no.5,pp.34-41, 2001.
.. [#] D. Ruderman, T. Cronin, and C. Chiao, "Statistics of cone responses
to natural images: implications for visual coding," J. Opt. Soc. Am. A
vol.15, pp.2036-2045, 1998.
"""
# convert input image to LAB color space
im_lab = color_conversion.rgb_to_lab(im_src)
# mask out irrelevant tissue / whitespace / etc
if mask_out is not None:
mask_out = mask_out[..., None]
im_lab = np.ma.masked_array(im_lab, mask=np.tile(mask_out, (1, 1, 3)))
# calculate src_mu and src_sigma if either is not provided
if (src_mu is None) or (src_sigma is None):
src_mu = [im_lab[..., i].mean() for i in range(3)]
src_sigma = [im_lab[..., i].std() for i in range(3)]
# scale to unit variance
for i in range(3):
im_lab[:, :, i] = (im_lab[:, :, i] - src_mu[i]) / src_sigma[i]
# rescale and recenter to match target statistics
for i in range(3):
im_lab[:, :, i] = im_lab[:, :, i] * target_sigma[i] + target_mu[i]
# convert back to RGB colorspace
im_normalized = color_conversion.lab_to_rgb(im_lab)
im_normalized[im_normalized > 255] = 255
im_normalized[im_normalized < 0] = 0
# return masked values and reconstruct unmasked LAB image
if mask_out is not None:
im_normalized = im_normalized.data
for i in range(3):
original = im_src[:, :, i].copy()
new = im_normalized[:, :, i].copy()
original[np.not_equal(mask_out[:, :, 0], True)] = 0
new[mask_out[:, :, 0]] = 0
im_normalized[:, :, i] = new + original
im_normalized = im_normalized.astype(np.uint8)
return im_normalized
def reinhard(im_src, target_mu, target_sigma, src_mu=None, src_sigma=None):
"""Performs Reinhard color normalization to transform the color
characteristics of an image to a desired standard.
The standard is defined by the mean and standard deviations of the target
image in LAB color space defined by Ruderman. The input image is converted
to Ruderman's LAB space, the LAB channels are each centered and scaled to
zero-mean unit variance, and then rescaled and shifted to match the target
image statistics. If the LAB statistics for the input image are provided
(`src_mu` and `src_sigma`) then these will be used for normalization,
otherwise they will be derived from the input image `im_src`.
Parameters
----------
im_src : array_like
An RGB image
target_mu : array_like
A 3-element array containing the means of the target image channels
in LAB color space.
target_sigma : array_like
A 3-element array containing the standard deviations of the target
image channels in LAB color space.
src_mu : array_like, optional
A 3-element array containing the means of the source image channels in
LAB color space. Used with reinhard_stats for uniform normalization of
tiles from a slide.
src_sigma : array, optional
A 3-element array containing the standard deviations of the source
image channels in LAB color space. Used with reinhard_stats for
uniform normalization of tiles tiles from a slide.
Returns
-------
im_normalized : array_like
Color Normalized RGB image
See Also
--------
histomicstk.preprocessing.color_conversion.rgb_to_lab,
histomicstk.preprocessing.color_conversion.lab_to_rgb
References
----------
.. [1] E. Reinhard, M. Adhikhmin, B. Gooch, P. Shirley, "Color transfer
between images," in IEEE Computer Graphics and Applications, vol.21,
no.5,pp.34-41, 2001.
.. [2] D. Ruderman, T. Cronin, and C. Chiao, "Statistics of cone responses
to natural images: implications for visual coding," J. Opt. Soc. Am. A
vol.15, pp.2036-2045, 1998.
"""
# get input image dimensions
m = im_src.shape[0]
n = im_src.shape[1]
# convert input image to LAB color space
im_lab = color_conversion.rgb_to_lab(im_src)
# calculate src_mu if not provided
if src_mu is None:
src_mu = im_lab.sum(axis=0).sum(axis=0) / (m * n)
# center to zero-mean
for i in range(3):
im_lab[:, :, i] = im_lab[:, :, i] - src_mu[i]
# calculate src_sigma if not provided
if src_sigma is None:
src_sigma = ((im_lab * im_lab).sum(axis=0).sum(axis=0) /
(m * n - 1))**0.5
# scale to unit variance
for i in range(3):
im_lab[:, :, i] = im_lab[:, :, i] / src_sigma[i]
# rescale and recenter to match target statistics
for i in range(3):
im_lab[:, :, i] = im_lab[:, :, i] * target_sigma[i] + target_mu[i]
# convert back to RGB colorspace
im_normalized = color_conversion.lab_to_rgb(im_lab)
im_normalized[im_normalized > 255] = 255
im_normalized[im_normalized < 0] = 0
im_normalized = im_normalized.astype(np.uint8)
return im_normalized
def reinhard(im_src, target_mu, target_sigma, src_mu=None, src_sigma=None):
"""Performs Reinhard color normalization to transform the color
characteristics of an image to a desired standard.
The standard is defined by the mean and standard deviations of the target
image in LAB color space defined by Ruderman. The input image is converted
to Ruderman's LAB space, the LAB channels are each centered and scaled to
zero-mean unit variance, and then rescaled and shifted to match the target
image statistics. If the LAB statistics for the input image are provided
(`src_mu` and `src_sigma`) then these will be used for normalization,
otherwise they will be derived from the input image `im_src`.
Parameters
----------
im_src : array_like
An RGB image
target_mu : array_like
A 3-element array containing the means of the target image channels
in LAB color space.
target_sigma : array_like
A 3-element array containing the standard deviations of the target
image channels in LAB color space.
src_mu : array_like, optional
A 3-element array containing the means of the source image channels in
LAB color space. Used with reinhard_stats for uniform normalization of
tiles from a slide.
src_sigma : array, optional
A 3-element array containing the standard deviations of the source
image channels in LAB color space. Used with reinhard_stats for
uniform normalization of tiles tiles from a slide.
Returns
-------
im_normalized : array_like
Color Normalized RGB image
See Also
--------
histomicstk.preprocessing.color_conversion.rgb_to_lab,
histomicstk.preprocessing.color_conversion.lab_to_rgb
References
----------
.. [1] E. Reinhard, M. Adhikhmin, B. Gooch, P. Shirley, "Color transfer
between images," in IEEE Computer Graphics and Applications, vol.21,
no.5,pp.34-41, 2001.
.. [2] D. Ruderman, T. Cronin, and C. Chiao, "Statistics of cone responses
to natural images: implications for visual coding," J. Opt. Soc. Am. A
vol.15, pp.2036-2045, 1998.
"""
# get input image dimensions
m = im_src.shape[0]
n = im_src.shape[1]
# convert input image to LAB color space
im_lab = color_conversion.rgb_to_lab(im_src)
# calculate src_mu if not provided
if src_mu is None:
src_mu = im_lab.sum(axis=0).sum(axis=0) / (m * n)
# center to zero-mean
for i in range(3):
im_lab[:, :, i] = im_lab[:, :, i] - src_mu[i]
# calculate src_sigma if not provided
if src_sigma is None:
src_sigma = ((im_lab * im_lab).sum(axis=0).sum(axis=0) /
(m * n - 1)) ** 0.5
# scale to unit variance
for i in range(3):
im_lab[:, :, i] = im_lab[:, :, i] / src_sigma[i]
# rescale and recenter to match target statistics
for i in range(3):
im_lab[:, :, i] = im_lab[:, :, i] * target_sigma[i] + target_mu[i]
# convert back to RGB colorspace
im_normalized = color_conversion.lab_to_rgb(im_lab)
im_normalized[im_normalized > 255] = 255
im_normalized[im_normalized < 0] = 0
im_normalized = im_normalized.astype(np.uint8)
return im_normalized
