Tkinter- resize images

''' tk_PIL_resize1.py
load and display an image with Tkinter

Tkinter only reads gif and ppm images
Use the Python Image Library (PIL) for other image formats
and for manipulating the image
Give Tkinter a namespace to avoid conflicts with PIL 
(they both have class Image) 
PIL is free from:
http://www.pythonware.com/products/pil/index.htm
I used Windows installer
PIL-1.1.7.win32-py2.7.exe
from:
http://effbot.org/downloads/#pil
'''

from PIL import Image, ImageTk
try:
    # Python2
    import Tkinter as tk
except ImportError:
    # Python3
    import tkinter as tk

root = tk.Tk()
w = 640
h = 500
cv = tk.Canvas(root, width=w, height=h)
cv.pack(fill='both', expand='yes')

# pick an image file you have .bmp  .jpg  .gif.  .png
# if not in the working directory, give full path
img_file = "flowers.jpg"
# open as a PIL image object
pil_image = Image.open(img_file)

# get the size of the original image
width_org, height_org = pil_image.size

# set the resizing factor so the aspect ratio is retained
# factor > 1.0 increases size
# factor < 1.0 decreases size
factor = 1.45
width = int(width_org * factor)
height = int(height_org * factor)
# use one of these filter options to resize the image:
# Image.NEAREST     use nearest neighbour
# Image.BILINEAR    linear interpolation in a 2x2 environment
# Image.BICUBIC     cubic spline interpolation in a 4x4 environment
# Image.ANTIALIAS   best down-sizing filter
pil_image2 = pil_image.resize((width, height), Image.ANTIALIAS)   

# optional title ...
sf = "{} ({}x{})".format(img_file, width, height)
root.title(sf)

# convert PIL image object to Tkinter PhotoImage object
tk_image = ImageTk.PhotoImage(pil_image2)

# 'nw' uses upper left corner of the image as anchor
# image corner positions at canvas coordinates x=30, y=20
#cv.create_image(30, 20, image=tk_image, anchor='nw')

# 'center' is default --> uses center of picture
# at canvas coordinates x=250, y=250 (center of canvas)
cv.create_image(w//2, h//2, image=tk_image, anchor='center')

root.mainloop()