generate fadeout image

make-fadeout-image.py

import os, sys, Image

# Usage $0 image width-for-new-file
filename = sys.argv[1] #'tv_main_bar_bg.png'
filename2 = '_fadeout'.join(os.path.splitext(filename))
width = int(sys.argv[2])
maxx = width - 1

im = Image.open(filename)
assert im.size[0] == 1
im2 = Image.new('RGBA', (width, im.size[1]))
for y in range(im.size[1]):
    r,g,b = im.getpixel((0, y))
    for x in range(width):
        xx = maxx - x
        alpha = 255 - (255 * xx * xx / maxx / maxx)
        im2.putpixel((x,y), (r,g,b,alpha))
im2.save(filename2)
import os;os.system('open '+filename2)