From 4ab4213749cb90cec574c8e066b921e6e162279f Mon Sep 17 00:00:00 2001
From: Tony S Yu <tsyu80@gmail.com>
Date: Mon, 12 Dec 2011 20:19:15 -0500
Subject: [PATCH] Change OpenCV import to make it an optional dependency

---
 skimage/detection/_template.pyx |  2 +-
 skimage/detection/template.py   | 10 +++++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/skimage/detection/_template.pyx b/skimage/detection/_template.pyx
index 3c6a726f..eb5a9733 100644
--- a/skimage/detection/_template.pyx
+++ b/skimage/detection/_template.pyx
@@ -3,9 +3,9 @@
 import cython
 cimport numpy as np
 import numpy as np
-import cv
 from scipy.signal import fftconvolve
 
+
 cdef extern from "math.h":
     double sqrt(double x)
     double fabs(double x)
diff --git a/skimage/detection/template.py b/skimage/detection/template.py
index e0ad01ef..6bf02896 100644
--- a/skimage/detection/template.py
+++ b/skimage/detection/template.py
@@ -1,9 +1,15 @@
 """template.py - Template matching
 """
 import numpy as np
-import cv
 import _template
 
+try:
+    import cv
+    opencv_available = True
+except ImportError:
+    opencv_available = False
+
+
 
 #XXX add to opencv backend once backend system in place
 def match_template_cv(image, template, out=None,  method="norm-coeff"):
@@ -23,6 +29,8 @@ def match_template_cv(image, template, out=None,  method="norm-coeff"):
         Correlation results between 0.0 and 1.0, maximum indicating the most
         probable match.
     """
+    if not opencv_available:
+        raise ImportError("Opencv 2.0+ required")
     if out == None:
         out = np.empty((image.shape[0] - template.shape[0] + 1,
                         image.shape[1] - template.shape[1] + 1),