title: Get Image Filename from Image PIL
body: <p>Is it possible to get the filename of an Image I have already opened from an Image object? I checked the API, and the best I could come up with was the PIL.Image.info, but that appears to be empty when I check it.
  Is there something else I can use to get this info in the PIL Image library?</p>
  
  <p>(Yes, I realize I can pass the filename into the function. I am looking for another way to do this.)</p>
  
  <p>i.e.</p>
  
  <pre><code>from PIL import Image
  
  def foo_img(img_input):
    filename = img_input.info["filename"]
    # I want this to print '/path/to/some/img.img'
    print(filename) 
  
  foo_img(Image.open('/path/to/some/img.img'))
  </code></pre>