python + opencv 对图片纠斜的一种方法

import cv2
import numpy as np


def showImage(name, image):
    cv2.imshow(name, image)
    cv2.waitKey(0)
    cv2.destroyAllWindows()


def imageskew(url):
    #读取图片
    img = cv2.imread(url)
    #显示原图
    showImage("之前", img)


    #转为灰度图
    grayimg=cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)


    #灰度图像取反
    grayimg=cv2.bitwise_not(grayimg)


    #像素值大于0的坐标集合
    coordinates = np.column_stack(np.where(grayimg > 0))


    #计算旋转角度
    ang =cv2.minAreaRect(coordinates)[-1]
    if ang < 45:
        ang=-ang
    else:
        ang=90-ang


    #计算中心坐标
    height, width = img.shape[:2]
    center = (width / 2, height / 2)


    #获得仿射变化矩阵
    rotationmatrix = cv2.getRotationMatrix2D(center, ang, 1.0)


    #进行仿射变化
    rotatedimg = cv2.warpAffine(img, rotationmatrix, (width, height), borderMode = cv2.BORDER_REFLECT)


    #展示纠斜后的图片
    showImage("之后", rotatedimg)


#小角度左倾斜图片
imageskew("skewl.png")
#小角度右倾斜图片
imageskew("skewr.png")