From 8042dc2cd9df32cf33fa271e3c5261490c2fc187 Mon Sep 17 00:00:00 2001
From: blink1073 <steven.silvester@ieee.org>
Date: Mon, 21 Jul 2014 19:48:27 -0500
Subject: [PATCH] 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            | 17 ++++++++++++++++-
 skimage/color/tests/test_colorconv.py | 24 ++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/skimage/color/colorconv.py b/skimage/color/colorconv.py
index 8e8c3b41..938bb849 100644
--- a/skimage/color/colorconv.py
+++ b/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
diff --git a/skimage/color/tests/test_colorconv.py b/skimage/color/tests/test_colorconv.py
index 094873ae..2b435f67 100644
--- a/skimage/color/tests/test_colorconv.py
+++ b/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)