图像反转

import matplotlib.pyplot as plt
import numpy as np
import math
import cv2
img=cv2.imread('C:/Users/xpp/Desktop/Lena.png')#读取图像
cv2.imshow('Lena',img)
#获取圆形区域的中心坐标
x0=img.shape[0]//2
y0=img.shape[1]//2
#通过圆形区域半径构造展开后的图像
Lena_height=radius=img.shape[0]//2
Lena_width=int(2*math.pi*radius)
Lena_img=np.zeros((Lena_height,Lena_width,3),dtype="u1")
except_count=0
for j in range(Lena_width):
    theta=2*math.pi*(j/Lena_width)-1/2*math.pi
    for i in range(Lena_height):
        Lena_radius=radius-i
        x=Lena_radius*math.sin(theta)+x0
        y=Lena_radius*math.cos(theta)+y0
        x,y=int(x),int(y)
        try:
            Lena_img[i,j,:]=img[x,y,:]
        except:
            continue
print(except_count)
cv2.imwrite('C:/Users/xpp/Desktop/Lena.png',Lena_img)
cv2.imshow('Lena',Lena_img)
cv2.waitKey(0)