Bug report

Bug summary

The error

TypeError: numpy boolean subtract, the `-` operator, is deprecated, use the bitwise_xor, the `^` operator, or the logical_xor function instead.

occurs when adding a colorbar to a pcolormesh of a Boolean array.

Code for reproduction

import matplotlib.pyplot as plt
import numpy as np

x = np.random.rand(10,10)

b = x > .5

plt.pcolormesh(b)
plt.colorbar()

Actual outcome

Expected outcome

I'm not sure if this is really a bug, or if the error is by design, but I expected matplotlib to treat the bool array as 1s and 0s without intervention.
To get the colorbar to work, I changed the array dtype from bool to int.

import matplotlib.pyplot as plt
import numpy as np

x = np.random.rand(10,10)

b = np.array(x>.5, dtype=int)  # works as expected with this change

plt.pcolormesh(b)
plt.colorbar()

Matplotlib version

• Operating system: Linux
• Matplotlib version: 3.1.1
• Matplotlib backend (print(matplotlib.get_backend())): module://ipykernel.pylab.backend_inline
• Python version: 3.7.0
• Jupyter version (if applicable): jupyterlab 1.2.6 (via conda-forge)
• Other libraries:

Matplotlib installed via conda, default channel

Thanks for looking into this and I hope the feedback is useful.