from PIL import Image
import sys

filename = sys.argv[1]
try:
    newname = sys.argv[4]
except IndexError:
    newname = None
i = Image.open(filename)
if all(x.isdigit() for x in sys.argv[2:3]):
    new_x = int(sys.argv[2])
    new_y = int(sys.argv[3])
else:
    try:
        ratio = float(sys.argv[2])
        new_x = int(i.size[0] * ratio)
        new_y = int(i.size[1] * ratio)
    except ValueError:
        print('you did it wrong')
        quit()

def fit_into_bounds(image_width, image_height, frame_width, frame_height):
    '''
    Given the w+h of the image and the w+h of the frame,
    return new w+h that fits the image into the frame
    while maintaining the aspect ratio.

    (1920, 1080, 400, 400) -> (400, 225)
    '''
    width_ratio = frame_width / image_width
    height_ratio = frame_height / image_height
    ratio = min(width_ratio, height_ratio)

    new_width = int(image_width * ratio)
    new_height = int(image_height * ratio)

    return (new_width, new_height)

(image_width, image_height) = i.size

if new_x == 0:
    (new_x, new_y) = fit_into_bounds(image_width, image_height, 10000000, new_y)
if new_y == 0:
    (new_x, new_y) = fit_into_bounds(image_width, image_height, new_x, 10000000)

print(i.size, new_x, new_y)
i = i.resize( (new_x, new_y), Image.ANTIALIAS)
if newname is None:
    if '.' in filename:
        suffix = '_{width}x{height}'.format(width=new_x, height=new_y)
        newname = filename.replace('.', suffix + '.')
    else:
        newname += suffix
i.save(newname, quality=100)