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

I was trying to resize some images for a slideshow video and because of that, I wanted not just one max dimension, but a max width and a max height (the size of the video frame).
And there was always the possibility of a portrait video...
The Image.thumbnail method was promising, but I could not make it upscale a smaller image.

So after I couldn't find an obvious way to do that here (or at some other places), I wrote this function and put it here for the ones to come:

from PIL import Image

def get_resized_img(img_path, video_size):
    img = Image.open(img_path)
    width, height = video_size  # these are the MAX dimensions
    video_ratio = width / height
    img_ratio = img.size[0] / img.size[1]
    if video_ratio >= 1:  # the video is wide
        if img_ratio <= video_ratio:  # image is not wide enough
            width_new = int(height * img_ratio)
            size_new = width_new, height
        else:  # image is wider than video
            height_new = int(width / img_ratio)
            size_new = width, height_new
    else:  # the video is tall
        if img_ratio >= video_ratio:  # image is not tall enough
            height_new = int(width / img_ratio)
            size_new = width, height_new
        else:  # image is taller than video
            width_new = int(height * img_ratio)
            size_new = width_new, height
    return img.resize(size_new, resample=Image.LANCZOS)