Bug report

Closed #8542 and opened this slightly modified version which better illustrates the problem.

Bug summary
When using the TK backend, savefig() with type='png' produces different image sizes, depending on the dpi argument when calling figure().

Code for reproduction

from pylab import *
%matplotlib tk

figsize = (10/3.0, 1)

plt.figure(figsize=figsize,dpi=100)
plt.savefig("100-300dpi.png",type="png",dpi=300)

plt.figure(figsize=figsize,dpi=96) #96 is my screen DPI
plt.savefig("96-300dpi.png",type="png",dpi=300)

Actual outcome

100-300dpi.png is 999x300 pixels.
96-300dpi.png is 1000x300 pixels.

Expected outcome

I would expect both to come out at 1000x300 pixels.

Matplotlib version

• Matplotlib 2.0.0
• Python 2.7.13
• IPython 5.1.0
• Jupyter Version: 4.4.1
• Platform: Linux