Inconsistent inset_axes position between show(), savefig(format='png') and savefig(format='pdf') #8120

Bug report

Bug summary

inset_axes inconsistently positioned between show(), savefig(...,format='png') and savefig(...format='pdf') when the dpi option is set.

Code for reproduction

import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1.inset_locator import inset_axes

fig = plt.figure(dpi=150);

ax1 = plt.gca()
ax1ins1 = inset_axes(ax1, width=.7, height=.7,bbox_to_anchor=(100,100))

plt.savefig("test.pdf",format='pdf',dpi=300,bbox_inches="tight")
plt.savefig("test.png",format='png',dpi=300,bbox_inches="tight")
plt.show()

Actual outcome

PDF:

PNG:

show():

Expected outcome

I would expect all the results to come out the same.

Matplotlib version

• Matplotlib 2.0.0 (conda)
• Python 2.7.13 (conda)
• Platform: Linux