@stefanv @ahojnnes : With the latest implementation, this what I get : 
```py
>>> from skimage.data import lena
>>> from skimage.color import rgb2gray
>>> from skimage.feature import censure_keypoints
>>> import numpy as np
>>> from time import time
>>> img = lena()
>>> img = rgb2gray(img)
>>> start = time()
>>> s = censure_keypoints(img, 7, 'Octagon')
1
2
3
4
7
8
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "skimage/feature/censure.py", line 163, in censure_keypoints
    scales = _get_filtered_image(image, no_of_scales, mode)
  File "skimage/feature/censure.py", line 32, in _get_filtered_image
    integral_img2 = _slanted_integral_image_modes(image, 2)
  File "skimage/feature/censure.py", line 69, in _slanted_integral_image_modes
    _slanted_integral_image(image, mode2)
  File "censure_cy.pyx", line 25, in skimage.feature.censure_cy._slanted_integral_image (skimage/feature/censure_cy.c:2149)
  File "stringsource", line 619, in View.MemoryView.memoryview_cwrapper (skimage/feature/censure_cy.c:11381)
  File "stringsource", line 327, in View.MemoryView.memoryview.__cinit__ (skimage/feature/censure_cy.c:8144)
ValueError: ndarray is not C-contiguous

```
I have made sure both the input arrays to `slanted_integral_image` are C-contiguous, but still get the above error. What am I missing?