Hi, I'm plotting this simple graph and I got non equal pixel sizes for the graph, it happens with all kind of sizes and dpi.
(I'm using matplotlib 1.5.0, python 3.5.1)
I can prove with some pictures as well if needed (I'm not sure if the bug is in matplotlib or in the renderer).

from matplotlib import use
use('Agg')
import matplotlib.pyplot as plt
import numpy as np

t = np.random.randn(64, 64)
fig, ax = plt.subplots()
ax.imshow(t, interpolation='none', origin="lower")
plt.savefig(
    'crap29.png',
    format='png'
)
plt.close()`

Thanks