crop fails for np.int64

[ianhi]

Description

skimage.util.crop fails when passed a numpy integer object. See numpy/numpy#2951 for discussion as to why. I believe the fix is to check for numbers.Integral (I'll send PR)

Way to reproduce

import numpy as np
from skimage.util import crop
image = np.arange(100).reshape(10,10)

# this works
crop(image, 2)

# this breaks
crop(image, np.int64(2))


# this comes up when doing something like
for crop_factor in np.arange(2,10):
    tmp = crop(image, crop_factor)
    # do something

Version information

# Paste the output of the following python commands
from __future__ import print_function
import sys; print(sys.version)
import platform; print(platform.platform())
import skimage; print("scikit-image version: {}".format(skimage.__version__))
import numpy; print("numpy version: {}".format(numpy.__version__))

3.8.5 (default, Sep  4 2020, 07:30:14) 
[GCC 7.3.0]
Linux-5.8.0-7642-generic-x86_64-with-glibc2.10
scikit-image version: 0.18.1
numpy version: 1.20.3