Python OpenCV輪廓排序(按照面積大小)

OpenCV輪廓排序(按照面積大小)，原圖以下：

代碼以下：

import cv2
import numpy as np

# putText函數使用的字體定義
font = cv2.FONT_HERSHEY_SIMPLEX
PI = 3.1415926
 
# 讀取圖片、灰度轉換、OTSU閾值
img = cv2.imread("test.png")
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
ret,thresh = cv2.threshold(gray,0,255,cv2.THRESH_BINARY_INV+cv2.THRESH_OTSU)
# 查看二值化結果
cv2.imshow("thres", thresh)
cv2.imwrite("thres.jpg", thresh)

# 輪廓查找
_, contours,hierarchy = cv2.findContours(thresh, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)

def cnt_area(cnt):
  area = cv2.contourArea(cnt)
  return area

contours.sort(key = cnt_area, reverse=False)
for i in range(0, len(contours)):
  (x, y, w, h) = cv2.boundingRect(contours[i])
  cv2.rectangle(img,(x,y),(x+w, y+h),(255,0,0),2, cv2.LINE_AA)
  cv2.putText(img,"No.%d"%(i+1),(x,y-5),font,0.8,(255,0,0),2)

cv2.imshow("contours", img)
cv2.imwrite("result1.jpg",img)
cv2.waitKey(0)
cv2.destroyAllWindows()

結果以下(面積從小到大，從大到小)：

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