图像旋转矫正

import cv2
import numpy as np
import math
def fourier_demo():
    img=cv2.imread('C:/Users/xpp/Desktop/Lena.png',0)
    h,w=img.shape[:2]
    new_h=cv2.getOptimalDFTSize(h)
    new_w=cv2.getOptimalDFTSize(w)
    right=new_w-w
    bottom=new_h-h
    result1=cv2.copyMakeBorder(img,0,bottom,0,right,borderType=cv2.BORDER_CONSTANT,value=0)
    cv2.imshow('result1',result1)
    #傅里叶变换
    f=np.fft.fft2(result1)
    fshift=np.fft.fftshift(f)
    magnitude=np.log(np.abs(fshift))
    #二值化
    magnitude_uint=magnitude.astype(np.uint8)
    ret, thresh=cv2.threshold(magnitude_uint,11,255,cv2.THRESH_BINARY)
    print(ret)
    cv2.imshow('thresh',thresh)
    print(thresh.dtype)
    #霍夫直线变换
    lines=cv2.HoughLinesP(thresh,2,np.pi/180,30,minLineLength=40,maxLineGap=100)
    print(len(lines))
    lineimg=np.ones(nimg.shape,dtype=np.uint8)
    lineimg=lineimg*255
    piThresh=np.pi/180
    pi2=np.pi/2
    print(piThresh)
    for line in lines:
        x1,y1,x2,y2=line[0]
        cv2.line(lineimg,(x1,y1),(x2,y2),(0,255,0),2)
        if x2-x1==0:
            continue
        else:
            theta=(y2-y1)/(x2-x1)
        if abs(theta)<piThresh or abs(theta-pi2)<piThresh:
            continue
        else:
            print(theta)
    angle=math.atan(theta)
    print(angle)
    angle=angle*(180/np.pi)
    print(angle)
    angle=(angle-90)/(w/h)
    print(angle)
    center=(w//2,h//2)
    M=cv2.getRotationMatrix2D(center,angle,1.0)
    rotated=cv2.warpAffine(img,M,(w,h),flags=cv2.INTER_CUBIC,borderMode=cv2.BORDER_REPLICATE)
    cv2.imshow('line image',lineimg)
    cv2.imshow('rotated',rotated)
fourier_demo()
cv2.waitKey(0)
cv2.destroyAllWindows()