Bug report

I would like to use matplotlib to render a figure, and convert the figure to RGB images. I expect the output image to be of certain pixel resolution W x H.

Many online resources (eg.. https://stackoverflow.com/questions/13714454/specifying-and-saving-a-figure-with-exact-size-in-pixels) suggests the following, but works most of the time but does not work in the following case:
Code for reproduction

import matplotlib as mpl
import matplotlib.figure as mplfigure
from matplotlib.backends.backend_agg import FigureCanvasAgg
width = 956
height = 928
fig = mplfigure.Figure(frameon=False)
dpi = fig.get_dpi()
print(dpi)
fig.set_size_inches(width / dpi, height / dpi)
canvas = FigureCanvasAgg(fig)
fig.savefig("out.png")
s, (w, h) = canvas.print_to_buffer()
print(w, h)

Actual outcome

100.0
956 927

Expected outcome

I expect 928.

Matplotlib version

• Operating system: archlinux
• Matplotlib version: 3.0.3
• Matplotlib backend (print(matplotlib.get_backend())): not sure if applicable to my snippet
• Python version: 3.7
• Jupyter version (if applicable):
• Other libraries:
  matplotlib was installed by pip install