diff --git a/skimage/segmentation/_felzenszwalb_cy.pyx b/skimage/segmentation/_felzenszwalb_cy.pyx
index 3babb86e..8590e17d 100644
--- a/skimage/segmentation/_felzenszwalb_cy.pyx
+++ b/skimage/segmentation/_felzenszwalb_cy.pyx
@@ -12,7 +12,8 @@ from skimage.morphology.ccomp cimport find_root, join_trees
 from ..util import img_as_float
 
 
-def _felzenszwalb_grey(image, double scale=1, sigma=0.8, Py_ssize_t min_size=20):
+def _felzenszwalb_grey(image, double scale=1, sigma=0.8,
+                       Py_ssize_t min_size=20):
     """Felzenszwalb's efficient graph based segmentation for a single channel.
 
     Produces an oversegmentation of a 2d image using a fast, minimum spanning
diff --git a/skimage/segmentation/_slic.pyx b/skimage/segmentation/_slic.pyx
index bfa6cd1a..5df747ad 100644
--- a/skimage/segmentation/_slic.pyx
+++ b/skimage/segmentation/_slic.pyx
@@ -2,15 +2,11 @@
 #cython: boundscheck=False
 #cython: nonecheck=False
 #cython: wraparound=False
-import collections as coll
 import numpy as np
-from time import time
 from scipy import ndimage
 
-cimport numpy as cnp
-
-from ..util import img_as_float, regular_grid
-from ..color import rgb2lab, gray2rgb
+from skimage.util import img_as_float, regular_grid
+from skimage.color import rgb2lab, gray2rgb
 
 
 def _slic_cython(double[:, :, :, ::1] image_zyx,
@@ -19,18 +15,18 @@ def _slic_cython(double[:, :, :, ::1] image_zyx,
                  double[:, ::1] means,
                  Py_ssize_t max_iter, Py_ssize_t n_segments):
     """Helper function for SLIC segmentation.
-    
+
     Parameters
     ----------
-    image_zyx : 4D np.ndarray of double, shape (Z, Y, X, 6)
+    image_zyx : 4D array of double, shape (Z, Y, X, 6)
         The image with embedded coordinates, that is, `image_zyx[i, j, k]` is
         `array([i, j, k, r, g, b])` or `array([i, j, k, L, a, b])`, depending
         on the colorspace.
-    nearest_mean : 3D np.ndarray of int, shape (Z, Y, X)
+    nearest_mean : 3D array of int, shape (Z, Y, X)
         The (initially empty) label field.
-    distance : 3D np.ndarray of double, shape (Z, Y, X)
+    distance : 3D array of double, shape (Z, Y, X)
         The (initially infinity) array of distances to the nearest centroid.
-    means : 2D np.ndarray of double, shape (n_segments, 6)
+    means : 2D array of double, shape (n_segments, 6)
         The centroids obtained by SLIC.
     max_iter : int
         The maximum number of k-means iterations.
@@ -39,7 +35,7 @@ def _slic_cython(double[:, :, :, ::1] image_zyx,
 
     Returns
     -------
-    nearest_mean : 3D np.ndarray of int, shape (Z, Y, X)
+    nearest_mean : 3D array of int, shape (Z, Y, X)
         The label field/superpixels found by SLIC.
     """
 
diff --git a/skimage/transform/_warps_cy.pyx b/skimage/transform/_warps_cy.pyx
index f51eb8d3..0eb7efdd 100644
--- a/skimage/transform/_warps_cy.pyx
+++ b/skimage/transform/_warps_cy.pyx
@@ -83,10 +83,8 @@ def _warp_fast(cnp.ndarray image, cnp.ndarray H, output_shape=None,
 
     """
 
-    cdef cnp.ndarray[dtype=cnp.double_t, ndim=2, mode="c"] img = \
-         np.ascontiguousarray(image, dtype=np.double)
-    cdef cnp.ndarray[dtype=cnp.double_t, ndim=2, mode="c"] M = \
-         np.ascontiguousarray(H)
+    cdef double[:, ::1] img = np.ascontiguousarray(image, dtype=np.double)
+    cdef double[:, ::1] M = np.ascontiguousarray(H)
 
     if mode not in ('constant', 'wrap', 'reflect', 'nearest'):
         raise ValueError("Invalid mode specified.  Please use "
@@ -101,8 +99,7 @@ def _warp_fast(cnp.ndarray image, cnp.ndarray H, output_shape=None,
         out_r = output_shape[0]
         out_c = output_shape[1]
 
-    cdef cnp.ndarray[dtype=cnp.double_t, ndim=2] out = \
-         np.zeros((out_r, out_c), dtype=np.double)
+    cdef double[:, ::1] out = np.zeros((out_r, out_c), dtype=np.double)
 
     cdef Py_ssize_t tfr, tfc
     cdef double r, c
@@ -122,8 +119,8 @@ def _warp_fast(cnp.ndarray image, cnp.ndarray H, output_shape=None,
 
     for tfr in range(out_r):
         for tfc in range(out_c):
-            _matrix_transform(tfc, tfr, <double*>M.data, &c, &r)
-            out[tfr, tfc] = interp_func(<double*>img.data, rows, cols, r, c,
+            _matrix_transform(tfc, tfr, &M[0, 0], &c, &r)
+            out[tfr, tfc] = interp_func(&img[0, 0], rows, cols, r, c,
                                         mode_c, cval)
 
     return out