From 24bab75dc340b2ca109e4301eebe25bbfd27ace9 Mon Sep 17 00:00:00 2001
From: Juan Nunez-Iglesias <juan.n@unimelb.edu.au>
Date: Fri, 17 Jun 2016 17:56:52 -0400
Subject: [PATCH] Check types with issubdtype

---
 skimage/feature/texture.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/skimage/feature/texture.py b/skimage/feature/texture.py
index 0669de37..689baa5c 100644
--- a/skimage/feature/texture.py
+++ b/skimage/feature/texture.py
@@ -116,8 +116,7 @@ def greycomatrix(image, distances, angles, levels=None, symmetric=False,
                          "other than uint8. The resulting matrix will be at "
                          "least levels ** 2 in size.")
 
-    if (image.dtype in (np.int8, np.int16, np.int32, np.int64) and
-                                                        np.any(image < 0)):
+    if np.issubdtype(image.dtype, np.signedinteger) and np.any(image < 0):
         raise ValueError("Negative-valued images are not supported.")
 
     if levels is None: