Added docs, tests for downsample() in skimage.transform._warps

skimage/transform/tests/test_warps.py

@@ -1,4 +1,4 @@
-from numpy.testing import assert_array_almost_equal, run_module_suite
+from numpy.testing import assert_array_almost_equal, run_module_suite, assert_array_equal
 import numpy as np
 from scipy.ndimage import map_coordinates
 
@@ -193,6 +193,33 @@ def test_warp_coords_example():
     coords = warp_coords(tform, (30, 30, 3))
     map_coordinates(image[:, :, 0], coords[:2])
 
+def test_downsample_sum():
+    """Verifying downsampling of an array with expected result in sum mode"""
+    image1 = np.arange(4*6).reshape(4, 6)
+    out1 = tf.downsample(image1, (2, 3))
+    expected1 = np.array([[ 24,  42],
+                          [ 96, 114]])
+    assert_array_equal(expected1, out1)
+    image2 = np.arange(5*8).reshape(5, 8)
+    out2 = tf.downsample(image2, (3, 3))
+    expected2 = np.array([[ 81, 108,  87],
+                          [174, 192, 138]])
+    assert_array_equal(expected2, out2)
+
+
+def test_downsample_mean():
+    """Verifying downsampling of an array with expected result in mean mode"""
+    image1 = np.arange(4*6).reshape(4, 6)
+    out1 = tf.downsample(image1, (2, 3), 'mean')
+    expected1 = np.array([[  4.,   7.],
+                          [ 16.,  19.]])
+    assert_array_equal(expected1, out1)
+    image2 = np.arange(5*8).reshape(5, 8)
+    out2 = tf.downsample(image2, (4, 5), 'mean')
+    expected2 = np.array([[ 14. ,  10.8],
+                          [  8.5,   5.7]])
+    assert_array_equal(expected2, out2)
+
 
 if __name__ == "__main__":
     run_module_suite()