# -*- coding: utf-8 -*-
__author__ = '上海色宁'

import sys
import cv2
import matplotlib.pyplot as plt
 
#计算方差
def getss(list):
    #计算平均值
    avg=sum(list)/len(list)
    #定义方差变量ss，初值为0
    ss=0
    #计算方差
    for l in list:
        ss+=(l-avg)*(l-avg)/len(list)
    #返回方差
    return ss
 
#获取每行像素平均值
def getdiff(img):
    #定义边长
    Sidelength=30
    #缩放图像
    img=cv2.resize(img,(Sidelength,Sidelength),interpolation=cv2.INTER_CUBIC)
    #灰度处理
    gray=cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
    #avglist列表保存每行像素平均值
    avglist=[]
    #计算每行均值，保存到avglist列表
    for i in range(Sidelength):
        avg=sum(gray[i])/len(gray[i])
        avglist.append(avg)
    #返回avglist平均值
    return avglist
 
#读取测试图片
img1=cv2.imread(sys.argv[1])
#ret, binary1 = cv2.threshold(img1,127,255,cv2.THRESH_BINARY_INV)
ret, binary1 = cv2.threshold(img1,0,255,cv2.THRESH_TRIANGLE)


diff1=getdiff(binary1)
print('img1:',getss(diff1))
 
#读取测试图片
img11=cv2.imread(sys.argv[2])
#ret, binary11 = cv2.threshold(img11,127,255,cv2.THRESH_BINARY_INV)
ret, binary11 = cv2.threshold(img11,0,255,cv2.THRESH_TRIANGLE)

diff11=getdiff(binary11)
print('img11:',getss(diff11))
 
ss1=getss(diff1)
ss2=getss(diff11)
print("两张照片的方差为：%s"%(abs(ss1-ss2)))
 
 
'''
x=range(30)
plt.figure("avg")
plt.plot(x,diff1,marker="*",label="$jiames$")
plt.plot(x,diff11,marker="*",label="$durant$")
plt.title("avg")
plt.legend()
plt.show()
'''
 
#cv2.waitKey(0)
#cv2.destroyAllWindows()