Description

Using a stretch norm is different on the development version of Matplotlib. The issue (see below for an example) bisects to the following change in Matplotlib: matplotlib/matplotlib@146856b, part of matplotlib/matplotlib#20054. It's not clear to me whether this is something that needs to be fixed in Matplotlib, or something needs changing in astropy.

Steps to Reproduce

import matplotlib.pyplot as plt
import numpy as np

from astropy.visualization import ImageNormalize, AsinhStretch

fig, ax = plt.subplots(figsize=(6, 2))
data = np.atleast_2d(np.linspace(0, 0.9, 10))
# data == [[0.  0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9]]
im = ax.imshow(data, norm=ImageNormalize(vmin=0, vmax=1, stretch=AsinhStretch()), cmap='prism')
fig.colorbar(im, orientation='horizontal')
plt.show()

Image before Matplotlib change:

Image after Matplotlib change:

Note how the colorbar is now stretched insetad of the ticks.

System Details

macOS-10.16-x86_64-i386-64bit
Python 3.9.1 (default, Dec 11 2020, 06:28:49)
[Clang 10.0.0 ]
Numpy 1.19.3
astropy 4.3.dev1547+gb52c40715
Scipy 1.5.4
Matplotlib 3.4.2.post948+g08f4629d91