pyhon+OpenCV中的快速直線檢測

資料來源: https://mp.weixin.qq.com/s?__biz=MjM5NTE3NjY5MA==&mid=2247484994&idx=2&sn=87f2e3a51b676869cf8fa304a66ee405&chksm=a6fdcfdf918a46c9fb3c2650f52eb0a9cba4ee774d9d67f1ff4c702c474cfb0fba6cec0e7000&scene=126&sessionid=1602570759&key=7674ee21d747fecf4d688b2265e9fd4d3e837e5865a5347d6a608bec91ddeb389beef52ec1c331beb1a06355f24523b2b92947eb0070be30fba359b9ed2d05df78292fdf1afb8b6ed386ffdd5b0eed163d94aebe4c433011a06a4b689294fc0559f8cb9c5559b419757877484a4703a1ba24bc02810a9338b65a60d84e658373&ascene=1&uin=MjIwODk2NDgxNw%3D%3D&devicetype=Windows+10+x64&version=6300002f&lang=zh_TW&exportkey=Al4BY6AoJqeuKxr5Rr8Erz8%3D&pass_ticket=t2NSb%2Bmc8NuxLUwFdAJLJl1KiHlj2yfEDRJjrQVKi3LX0NhUF%2FzRbYtuCFbskDVs&wx_header=0

cv::ximgproc::FastLineDetectors是opencv-contrib中用於檢測直線的模塊，該方法能夠在垂直方向獲得精度更高的直線檢測結果，並且不需要調節參數。該函數是LineSegmentDetector因版權問題從OpenCV中可移除後最易用的直線檢測小能手，沒有一個。此處介紹該功能的使用方法其輸出結果剖析。

環境

    python3.6
    opencv-contrib-python 4.4.0.44
        [pip uninstall opencv-python]
        [pip install opencv-contrib-python]    

        

PS.在OpenCV 4.1.0之前的版本中，有一個LineSegmentDetector模塊，功能強大，檢測直線非常方便，但該函數因為版權問題已在4.1.X版本上已刪除，故此處不討論此方案。LineSegmentDetector相關的問題可以參考：

python的線段檢測器的任何實現

https://answers.opencv.org/question/215800/any-implementation-of-linesegmentdetector-for-python/

需要刪除LineSegmentDetector以獲得許可證

https://github.com/WPIRoboticsProjects/GRIP/issues/961

FastLineDetectors應用示例01

import cv2 
import numpy as np 
img = cv2.imread('sudo.png') 
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) 
#Create default Fast Line Detector (FSD) 
fld = cv2.ximgproc.createFastLineDetector() 
#Detect lines in the image 
lines = fld.detect(gray) 
#Draw detected lines in the image 
drawn_img = fld.drawSegments(gray,lines) 
cv2.imshow("FLD", drawn_img) 
cv2.waitKey(0)

FastLineDetectors應用示例02

import cv2
import numpy as np
from scipy.spatial import distance as dist

img = cv2.imread('sDQLM.png')
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

#Create default Fast Line Detector (FSD)
fld = cv2.ximgproc.createFastLineDetector()

#Detect lines in the image
lines = fld.detect(gray)

dMax = 0
bx_Max = 0
by_Max = 0
ex_Max = 0
ey_Max = 0

for L in lines:
   bx,by,ex,ey = L[0]
   # compute the Euclidean distance between the two points,
   D = dist.euclidean((bx, by), (ex, ey))
   
   if D > dMax:
       dMax = D
       bx_Max = bx
       by_Max = by
       ex_Max = ex
       ey_Max = ey
       
lineMax = np.array([[[bx_Max, by_Max, ex_Max,ey_Max]]])
#Draw detected lines in the image
drawn_img = fld.drawSegments(gray,lineMax,True)
cv2.circle(drawn_img, (bx_Max, by_Max), 1, (255,0,0), 2)#line begin
cv2.circle(drawn_img, (ex_Max, ey_Max), 1, (0,255,0), 2)#line end

cv2.imshow("FLD", drawn_img)
cv2.waitKey(0)