When using the macosx backend, if MathTex is in a y-axis label, the resolution of the label is distorted. The horizontal axis labels display correctly. I tried a couple of other backends, and macosx seems to be the only one with this issue. I am using the current master branch, downloaded today.

From playing around with the source a bit, it seems like it is an issue introduced by #2665, specifically related to the draw_image_user_coords_device_size function added to src/_macosx.m. By changing back to the old function that was used, CGContextDrawImage, the problem seems to go away for me.

Below is some code that illustrates the issue.

import matplotlib as mpl
mpl.use('macosx')

import numpy as np
from matplotlib import pyplot as plt

x = np.linspace(0, 10, 11, endpoint=True)

fig, (ax1, ax2) = plt.subplots(2, 1)
fig.subplots_adjust(hspace=0.5)

y = np.random.rand(11)
ax1.plot(x, y)
ax1.set_xlabel('x label')
ax1.set_ylabel('y label')
ax1.set_title('plain labels')

y = np.random.rand(11)
ax2.plot(x, y)
ax2.set_xlabel('$x$ label')
ax2.set_ylabel('$y$ label')
ax2.set_title('labels with latex')

plt.show()