BUG: FutureWarning in distance_transform_cdt

[martinResearch]

Describe your issue.

Getting FutureWarning when using distance_transform_cdt with a metric that is a numpy array
FutureWarning: elementwise comparison failed; returning scalar instead, but in the future will perform elementwise comparison

In here

scipy/scipy/ndimage/_morphology.py

Line 2075 in 5057eff

if metric in ['taxicab', 'cityblock', 'manhattan']:

we need to replace

    if metric in ['taxicab', 'cityblock', 'manhattan']:
        rank = input.ndima
        metric = generate_binary_structure(rank, 1)
    elif metric == 'chessboard':
        rank = input.ndim
        metric = generate_binary_structure(rank, rank)

by

    if isintance(metric,str) and metric in ['taxicab', 'cityblock', 'manhattan']:
        rank = input.ndima
        metric = generate_binary_structure(rank, 1)
    elif  isintance(metric,str) and metric == 'chessboard':
        rank = input.ndim
        metric = generate_binary_structure(rank, rank)

Reproducing Code Example

from scipy impoirt ndimage
import numpy as np
ndimage.distance_transform_cdt(np.zeros((5,5), dtype=bool), metric=np.ones((3,3), dtype=bool))

Error message

<string>:1: FutureWarning: elementwise comparison failed; returning scalar instead, but in the future will perform elementwise comparison

SciPy/NumPy/Python version information

1.9.3

[tupui]

Good catch, thank you @martinResearch