python局部图像放大

import cv2 as cv
import sys

if __name__ == '__main__':
    #读取图像并判断是否读取成功
    img = cv.imread('tu.jpg')
    #需要放大的部分
    part = img[300:400,250:350]
    #双线性插值法
    mask = cv.resize(part, (300, 300), fx=0, fy=0, interpolation=cv.INTER_LINEAR)
    if img is None is None:
        print('Failed to read picture')
        sys.exit()
        
    #放大后局部图的位置img[210:410,670:870]
    img[110:410,570:870]=mask

    #画框并连线
    cv.rectangle(img,(250,300),(350,400),(0,255,0),1)
    cv.rectangle(img,(570,110),(870,410),(0,255,0),1)
    img = cv.line(img,(350,300),(570,110),(0,255,0))
    img = cv.line(img,(350,400),(570,410),(0,255,0))
    #展示结果
    cv.imshow('img',img)
    cv.waitKey(0)
    cv.destroyAllWindows()