How do I resize an image using PIL and maintain its aspect ratio?

Question

Is there an obvious way to do this that I\'m missing? I\'m just trying to make thumbnails.

Answer 1

Based in @tomvon, I finished using the following (pick your case):

a) Resizing height (I know the new width, so I need the new height)

new_width  = 680
new_height = new_width * height / width 

b) Resizing width (I know the new height, so I need the new width)

new_height = 680
new_width  = new_height * width / height

Then just:

img = img.resize((new_width, new_height), Image.ANTIALIAS)