Increase Dpi In Matplotlib Chart Without Changing It's Size

I'm trying to create a pdf using Python's reportlab module. I generated a png with matplotlib and saved it in the pdf file using report labs canvas.drawImage method. My problem is

Solution 1:

f = df.plot()
fig = f.get_figure()
fig.set_size_inches((2,2))
fig.savefig('C:/temp/foo.png', bbox_inches='tight', dpi=1500)