#-*- coding: utf-8 -*-
import os

#判断图像是否存在，不存在则下载
if os.path.isfile('cave.png'):
    pass
    #print 'existed'
else: #download the image
    import base64
    from urllib.request import Request,urlopen
    req = Request('http://www.pythonchallenge.com/pc/return/cave.jpg')
    auth = base64.encodebytes(b'%s:%s' % (b'huge',b'file')).decode('utf8').replace('\n','')
    req.add_header('Authorization','Basic %s' % auth)
    data = urlopen(req).read()
    with open('cave.png', 'wb') as f:
        f.write(data)

#图像处理
from PIL import Image #需要先下载安装PIL

try:
    #--打开图像
    image = Image.open('cave.png')
    print(image.format,image.size,image.mode) #PNG (629, 95) RGBA
    width, height = image.size
    imgOdd = Image.new('RGB',(width,height),0)
    imgEven = Image.new('RGB',(width,height),0)

    #--加载像素
    pixel = image.load()

    for y in range(0,height):
        for x in range(0,width):
            #print x,y,pixel[x,y]
            if (x+y)%2==0:
                imgEven.putpixel((x,y),pixel[x,y])
                #imgOdd.putpixel((x,y), (255,255,255))
            else:
                imgOdd.putpixel((x,y),pixel[x,y])
                #imgEven.putpixel((x,y), (255,255,255))
    
    imgEven.show()
    imgOdd.show()
    #image.show()
except IOError as e:
    print('Error', e)