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

from PIL import Image

img = Image.open('/your image path/image.jpg') # image extension *.png,*.jpg
new_width  = 200
new_height = 300
img = img.resize((new_width, new_height), Image.ANTIALIAS)
img.save('output image name.png') # format may what you want *.png, *jpg, *.gif

Answer 2

A simple method for keeping constrained ratios and passing a max width / height. Not the prettiest but gets the job done and is easy to understand:

def resize(img_path, max_px_size, output_folder):
    with Image.open(img_path) as img:
        width_0, height_0 = img.size
        out_f_name = os.path.split(img_path)[-1]
        out_f_path = os.path.join(output_folder, out_f_name)

        if max((width_0, height_0)) <= max_px_size:
            print('writing {} to disk (no change from original)'.format(out_f_path))
            img.save(out_f_path)
            return

        if width_0 > height_0:
            wpercent = max_px_size / float(width_0)
            hsize = int(float(height_0) * float(wpercent))
            img = img.resize((max_px_size, hsize), Image.ANTIALIAS)
            print('writing {} to disk'.format(out_f_path))
            img.save(out_f_path)
            return

        if width_0 < height_0:
            hpercent = max_px_size / float(height_0)
            wsize = int(float(width_0) * float(hpercent))
            img = img.resize((max_px_size, wsize), Image.ANTIALIAS)
            print('writing {} to disk'.format(out_f_path))
            img.save(out_f_path)
            return

Here's a python script that uses this function to run batch image resizing.