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Error handling for images with negative values in Image Correction methods

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This commit is contained in:
Ankit Agrawal
2013-05-21 13:00:49 +08:00
parent 23f61795eb
commit 00ae241525
2 changed files with 32 additions and 13 deletions
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skimage/exposure/exposure.py
+30 -11
View File
@@ -2,7 +2,7 @@ import warnings
import numpy as np
from skimage import img_as_float
from skimage.util.dtype import dtype_range
from skimage.util.dtype import dtype_range, dtype_limits
import skimage.color as color
from skimage.util.dtype import convert
from skimage._shared.utils import deprecated
@@ -257,7 +257,13 @@ def rescale_intensity_gamma(image, gamma=1, gain=1):
if gamma < 0:
return "Gamma should be a non-negative real number"
scale = float(dtype_range[dtype][1] - dtype_range[dtype][0])
if np.any(image < 0):
raise ValueError('Image Correction methods work correctly only on '
'images with non-negative values. Use '
'skimage.exposure.rescale_intensity.')
else:
scale = float(dtype_limits(image, True)[1] - dtype_limits(image, True)[0])
out = ((image / scale) ** gamma) * scale * gain
return dtype(out)
@@ -290,11 +296,17 @@ def rescale_intensity_log(image, gain=1, inv=False):
"""
dtype = image.dtype.type
scale = float(dtype_range[dtype][1] - dtype_range[dtype][0])
if inv == True:
out = (2 ** (image / scale) - 1) * scale * gain
return dtype(out)
if np.any(image < 0):
raise ValueError('Image Correction methods work correctly only on '
'images with non-negative values. Use '
'skimage.exposure.rescale_intensity.')
else:
scale = float(dtype_limits(image, True)[1] - dtype_limits(image, True)[0])
if inv == True:
out = (2 ** (image / scale) - 1) * scale * gain
return dtype(out)
out = np.log2(1 + image / scale) * scale * gain
return dtype(out)
@@ -331,9 +343,16 @@ def rescale_intensity_sigmoid(image, cutoff=0.5, gain=10, inv=False):
"""
dtype = image.dtype.type
scale = float(dtype_range[dtype][1] - dtype_range[dtype][0])
if inv == True:
out = (1 - 1 / (1 + np.exp(gain * (cutoff - image/scale)))) * scale
if np.any(image < 0):
raise ValueError('Image Correction methods work correctly only on '
'images with non-negative values. Use '
'skimage.exposure.rescale_intensity.')
else:
scale = float(dtype_limits(image, True)[1] - dtype_limits(image, True)[0])
if inv == True:
out = (1 - 1 / (1 + np.exp(gain * (cutoff - image/scale)))) * scale
return dtype(out)
out = (1 / (1 + np.exp(gain * (cutoff - image/scale)))) * scale
return dtype(out)
out = (1 / (1 + np.exp(gain * (cutoff - image/scale)))) * scale
return dtype(out)
skimage/exposure/tests/test_exposure.py
+2 -2
View File
@@ -183,14 +183,14 @@ if __name__ == '__main__':
def test_rescale_intensity_gamma_one():
"""Same image should be returned for gamma equal to one"""
image = np.arange(0, 255, 4, np.uint8).reshape(8,8)
image = np.random.uniform(0, 255, (8, 8))
result = exposure.rescale_intensity_gamma(image, 1)
assert_array_equal(result, image)
def test_rescale_intensity_gamma_zero():
"""White image should be returned for gamma equal to zero"""
image = np.arange(0, 255, 4, np.uint8).reshape(8,8)
image = np.random.uniform(0, 255, (8, 8))
result = exposure.rescale_intensity_gamma(image, 0)
dtype = image.dtype.type
assert_array_equal(result, dtype_range[dtype][1])