opencv实现文档矫正

import cv2
import numpy as np
def imshow(img):
    cv2.imshow("img",img)
    cv2.waitKey(0)
    cv2.destroyAllWindows()
img = cv2.imread("2.png",1)
img = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) 
img2 = img.copy()
img_canny = cv2.Canny(img,75,200) 
img_line = cv2.HoughLines(img_canny,1,np.pi/180,280)
average = 0
for line in img_line: 
    for rho,theta in line:
        average = average + theta 
average = average / len(img_line)
angel = average/np.pi * 180 - 90
def rotateImg(img,angel):
    rows, cols = img.shape
    M = cv2.getRotationMatrix2D(((cols - 1) / 2.0, (rows - 1) / 2.0), angel, 1)  # 旋转中心x,旋转中心y，旋转角度，缩放因子
    img = cv2.warpAffine(img, M, (cols, rows),borderValue = (255,255,255))  #在内存里完成了旋转
    imshow(img)
rotateImg(img2,angle)

import cv2
import numpy as np
def imshow(img):
    cv2.imshow("img",img)
    cv2.waitKey(0)
    cv2.destroyAllWindows()
img = cv2.imread("2.png",1)
img = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) 
img2 = img.copy()
imgth = cv2.threshold(img,0,255,cv2.THRESH_OTSU|cv2.THRESH_BINARY_INV)[1]
kernel = np.ones((17,17))
img_open = cv2.morphologyEx(imgth,cv2.MORPH_CLOSE,kernel,10)
# imshow(img_open)
cons = cv2.findContours(img_open,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE)[0]
areas = []
for con in cons:
    area = cv2.contourArea(con)
    areas.append(area)
index = areas.index(max(areas))
# 度数形式，霍夫变换的返回值是弧度制
rect = cv2.minAreaRect(cons[index])
angle = rect[2]
mat = cv2.getRotationMatrix2D((img.shape[1]/2,img.shape[0]/2),angle,1)
img_fin = cv2.warpAffine(img,mat,(img.shape[1],img.shape[0]),borderValue = (255,255,255))
imshow(img_fin)