Resize and compress image using python

resize-image.py

from __future__ import division
from PIL import Image, ImageOps
import os, sys

HEIGHT = 675
WIDTH = 540
QUALITY = 60
OUTPUT_TYPE = "jpeg"

def getSize(i):
    return i.size    

def resize(i,w,h):
    return i.resize((int(w),int(h)),Image.ANTIALIAS).convert('RGB')

def save(i,w,h):
    n = str(w) + 'x' + str(h) + '~' + str(QUALITY) +  '.' + OUTPUT_TYPE
    i.save(n,optimize=True,quality=QUALITY)

def start():
    img = Image.open("./a.png")
    [w, h] = getSize(img)

    NEW_HEIGHT = HEIGHT
    NEW_WIDTH = WIDTH
    if h > w:
        r = w / h
        NEW_WIDTH = int( r * HEIGHT )
    elif w > h:
        r = h / w
        NEW_HEIGHT = int( r * WIDTH )

    img = resize(img,NEW_WIDTH,NEW_HEIGHT)
    delta_w = WIDTH - NEW_WIDTH
    delta_h = HEIGHT - NEW_HEIGHT
    padding = (delta_w//2, delta_h//2, delta_w-(delta_w//2), delta_h-(delta_h//2))
    new_im = ImageOps.expand(img, padding, fill=(255,255,255))
    save(new_im,WIDTH,HEIGHT)
start()