cv2.approxPolyDP() , cv2.arcLength() 这些是如何工作的

If you are looking for a example snippet, below is one:

import cv2
import imutils

# edged is the edge detected image
cnts = cv2.findContours(edged, cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
cnts = imutils.grab_contours(cnts)
cnts = sorted(cnts, key = cv2.contourArea, reverse = True)[:5]
# loop over the contours
for c in cnts:
    # approximate the contour
    peri = cv2.arcLength(c, True)
    approx = cv2.approxPolyDP(c, 0.02 * peri, True)
    # if our approximated contour has four points, then we
    # can assume that we have found our screen
    if len(approx) == 4:
        screenCnt = approx
        break

在上面的代码片段中，它首先从边缘检测图像中找到轮廓，然后对轮廓进行排序以找到五个最大的轮廓.最后，它遍历轮廓并使用 cv2.approxPolyDP 函数来平滑和逼近四边形.cv2.approxPolyDP 适用于文档边界等轮廓中有尖锐边缘的情况.