title: How to save a canvas as PNG in Selenium?
body: <p>I am trying to save a canvas element as a png image. This is my code right now but, unfortunately, it does not work:</p>
  
  <pre><code>import time
  from selenium import webdriver
  # From PIL import Imag.
  
  
  driver = webdriver.Firefox()
  driver.get('http://www.agar.io')
  driver.maximize_window()
  driver.find_element_by_id('freeCoins').click()
  
  time.sleep(2)
  
  # The part below does not seem to work properly.
  
  driver.execute_script('function download_image(){var canvas = document.getElementByTagName("canvas");canvas.toBlob(function(blob) {saveAs(blob, "../images/output.png");}, "image/png");};')
  </code></pre>
  
  <p>I would like to see the solution in Python. I would also like to see a solution that does not require cropping at the end of the screenshot.</p>