Fix holes in lab conversions and add tests

Fix holes in lab conversions and add tests

Fix holes in lab conversions and add tests

Add saturation protection and error raising by default

Trigger travis rebuild after error

Raise warning by default, change parameter name

skimage/color/colorconv.py

@@ -53,6 +53,7 @@ References
 
 from __future__ import division
 
+from warnings import warn
 import numpy as np
 from scipy import linalg
 from ..util import dtype
@@ -552,6 +553,8 @@ def xyz2rgb(xyz):
     mask = arr > 0.0031308
     arr[mask] = 1.055 * np.power(arr[mask], 1 / 2.4) - 0.055
     arr[~mask] *= 12.92
+    arr[arr < 0] = 0
+    arr[arr > 1] = 1
     return arr
 
 
@@ -808,7 +811,7 @@ def xyz2lab(xyz, illuminant="D65", observer="2"):
     return np.concatenate([x[..., np.newaxis] for x in [L, a, b]], axis=-1)
 
 
-def lab2xyz(lab, illuminant="D65", observer="2"):
+def lab2xyz(lab, illuminant="D65", observer="2", error_on_invalid=False):
     """CIE-LAB to XYZcolor space conversion.
 
     Parameters
@@ -819,6 +822,9 @@ def lab2xyz(lab, illuminant="D65", observer="2"):
         The name of the illuminant (the function is NOT case sensitive).
     observer : {"2", "10"}, optional
         The aperture angle of the observer.
+     error_on_invalid: optional, bool
+        If true, raise ValueError when pixels are outside the valid gamut.
+        Otherwise, raise a warning.
 
     Returns
     -------
@@ -854,6 +860,15 @@ def lab2xyz(lab, illuminant="D65", observer="2"):
     x = (a / 500.) + y
     z = y - (b / 200.)
 
+    if np.any(z < 0):
+        invalid = np.nonzero(z < 0)
+        msg = 'Color data out of range: Z < 0 in %s pixels' % invalid[0].size
+        if error_on_invalid:
+            raise ValueError(msg)
+        else:
+            warn(msg)
+            z[invalid] = 0
+
     out = np.dstack([x, y, z])
 
     mask = out > 0.2068966

skimage/color/tests/test_colorconv.py

@@ -11,6 +11,7 @@ Authors
 :license: modified BSD
 """
 
+from __future__ import division
 import os.path
 
 import numpy as np
@@ -372,6 +373,29 @@ class TestColorconv(TestCase):
         img_rgb = img_as_float(self.img_rgb)
         assert_array_almost_equal(luv2rgb(rgb2luv(img_rgb)), img_rgb)
 
+    def test_lab_rgb_outlier(self):
+        lab_array = np.ones((3, 1, 3))
+        lab_array[0] = [50, -12, 85]
+        lab_array[1] = [50, 12, -85]
+        lab_array[2] = [90, -4, -47]
+        rgb_array = np.array([[[0.501, 0.481, 0]],
+                              [[0, 0.482, 1.]],
+                              [[0.578, 0.914, 1.]],
+                              ])
+        assert_almost_equal(lab2rgb(lab_array), rgb_array, decimal=3)
+
+    def test_lab_full_gamut(self):
+        a, b = np.meshgrid(np.arange(-100, 100), np.arange(-100, 100))
+        L = np.ones(a.shape)
+        lab = np.dstack((L, a, b))
+        assert_raises(ValueError, lambda: lab2xyz(lab))
+        multipliers = [0, 10, 50, 100]
+        nan_percents = [12, 9, 0, 0]
+        for (l, perc) in zip(multipliers, nan_percents):
+            lab[:, :, 0] = l
+            out = lab2xyz(lab)
+            assert_equal(int(np.isnan(out).sum() / out.size * 100), perc)
+
     def test_lab_lch_roundtrip(self):
         rgb = img_as_float(self.img_rgb)
         lab = rgb2lab(rgb)