title: Increase dpi in matplotlib chart without changing it's size
body: <p>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 that the generated png file is very fuzzy. I specified the size in inches with plt.figure(figsize=(20,10)) and saved the picture with the plt.savefig method.<br>
  This works out perfectly (except the fuzzy quality of the picture).<br>
  But when I increase the dpi within the savefig method the size of the picture increases.<br>
  Is there any way to improve the dpi without changing the picture size.
  Or is there a way to resize it to the predefined values?</p>
  
  <p>Thanks! </p>