#!/usr/bin/env python
# -*- coding: utf-8 -*-
# -*- mode: python;Encoding: utf8n -*-
u"""
画像に変な暗号化をかけてみるPythonスクリプト

PIL(Pillow)を使用。

Usage:
    python imgcrypt.py IN_IMAGE OUT_IMAGE

"""

import sys
import os
from PIL import Image

next = 1

def rand():
    u"""乱数生成器(C言語のソレ)"""
    global next
    next = (next * 1103515245 + 12345) & 0xffffffff
    return int((next / 65536) % 32768)

def srand(seed):
    u"""乱数初期化。種を渡す。"""
    global next
    next = seed

def encrypt_image(img):
    u"""画像を難読化。Imageを渡す。"""
    outimg = img.copy()
    w, h = img.size
    srand(0)
    for y in range(h):
        rx = rand()
        for x in range(w):
            c = img.getpixel(((x + rx) % w, y))
            outimg.putpixel((x, y), c)
    return outimg

def decrypt_image(img):
    u"""画像の難読化の解除。Imageを渡す。"""
    outimg = img.copy()
    w, h = img.size
    srand(0)
    for y in range(h):
        rx = rand()
        for x in range(w):
            c = img.getpixel(((x - rx) % w, y))
            outimg.putpixel((x, y), c)
    return outimg

def main():
    if len(sys.argv) < 3:
        print "Usage: python %s IN_IMAGE OUT_IMAGE" % \
            os.path.basename( __file__ )
        sys.exit()

    inimgfn = sys.argv[1]
    if not os.path.isfile(inimgfn):
        print "Not Found %s" % inimgfn
        sys.exit()

    outimgfn = sys.argv[2]
    img = Image.open(inimgfn, "r")

    outimg = encrypt_image(img)

    if True:
        # 画像を保存
        outimg.save(outimgfn)
        print "Output %s" % outimgfn
    else:
        # 画像を表示して確認
        outimg.show()
        decrypt_image(outimg).show()

if __name__ == '__main__':
    main()