From 469b41b0206c205f652580abe4e0869c0c4e8c63 Mon Sep 17 00:00:00 2001
From: Chris Beaumont <beaumont@hawaii.edu>
Date: Thu, 4 Apr 2013 10:55:57 -0400
Subject: [PATCH] vectorized transform.integral.integrate

---
 skimage/transform/integral.py            | 35 +++++++++++++++---------
 skimage/transform/tests/test_integral.py | 15 ++++++++++
 2 files changed, 37 insertions(+), 13 deletions(-)

diff --git a/skimage/transform/integral.py b/skimage/transform/integral.py
index c34b6a19..3503a652 100644
--- a/skimage/transform/integral.py
+++ b/skimage/transform/integral.py
@@ -1,3 +1,6 @@
+import numpy as np
+
+
 def integral_image(x):
     """Integral image / summed area table.
 
@@ -34,28 +37,34 @@ def integrate(ii, r0, c0, r1, c1):
     ----------
     ii : ndarray
         Integral image.
-    r0, c0 : int
-        Top-left corner of block to be summed.
-    r1, c1 : int
-        Bottom-right corner of block to be summed.
+    r0, c0 : int or ndarray
+        Top-left corner(s) of block to be summed.
+    r1, c1 : int or ndarray
+        Bottom-right corner(s) of block to be summed.
 
     Returns
     -------
-    S : int
-        Integral (sum) over the given window.
+    S : scalar or ndarray
+        Integral (sum) over the given window(s).
 
     """
-    S = 0
+    if np.isscalar(r0):
+        r0, c0, r1, c1 = [np.asarray([x]) for x in (r0, c0, r1, c1)]
+
+    S = np.zeros(r0.shape, ii.dtype)
 
     S += ii[r1, c1]
 
-    if (r0 - 1 >= 0) and (c0 - 1 >= 0):
-        S += ii[r0 - 1, c0 - 1]
+    good = (r0 >= 1) & (c0 >= 1)
+    S[good] += ii[r0[good] - 1, c0[good] - 1]
 
-    if (r0 - 1 >= 0):
-        S -= ii[r0 - 1, c1]
+    good = r0 >= 1
+    S[good] -= ii[r0[good] - 1, c1[good]]
 
-    if (c0 - 1 >= 0):
-        S -= ii[r1, c0 - 1]
+    good = c0 >= 1
+    S[good] -= ii[r1[good], c0[good] - 1]
+
+    if S.size == 1:
+        return np.asscalar(S)
 
     return S
diff --git a/skimage/transform/tests/test_integral.py b/skimage/transform/tests/test_integral.py
index d443189c..ed973cec 100644
--- a/skimage/transform/tests/test_integral.py
+++ b/skimage/transform/tests/test_integral.py
@@ -26,6 +26,21 @@ def test_single():
     assert_equal(x[0, 0], integrate(s, 0, 0, 0, 0))
     assert_equal(x[10, 10], integrate(s, 10, 10, 10, 10))
 
+def test_vectorized_integrate():
+    r0 = np.array([12, 0, 0, 10, 0, 10, 30])
+    c0 = np.array([10, 0, 10, 0, 0, 10, 31])
+    r1 = np.array([23, 19, 19, 19, 0, 10, 49])
+    c1 = np.array([19, 19, 19, 19, 0, 10, 49])
+
+    expected = np.array([x[12:24, 10:20].sum(),
+                         x[:20, :20].sum(),
+                         x[:20, 10:20].sum(),
+                         x[10:20, :20].sum(),
+                         x[0,0],
+                         x[10, 10],
+                         x[30:, 31:].sum()])
+    assert_equal(expected, integrate(s, r0, c0, r1, c1))
+
 
 if __name__ == '__main__':
     run_module_suite()