用opencv python计算在一行中截取的点 [英] Counting the point which intercept in a line with opencv python

问题描述

我正在使用opencv和python编程进行车辆计数，我已经完成了以下步骤: 1.使用BackgroundSubtractorMOG2检测行驶中的车辆 2.在其上画一个矩形，然后将其重心 3.画一条线(以指示计数)

I am working in vehicle counting with opencv and python programming, I already complete step: 1. Detect moving vehicle with BackgroundSubtractorMOG2 2. Draw rectangle on it, then poin a centroid of that 3. Draw a line (to indicate of the counting)

如果该质心在行中加/截，我想算为1.，但是在我的代码中有时会添加no.这里是行代码:

if that centroid accros/intercept with the line I want count that 1. but in my code sometime it add sometime no. Here the line code:

cv2.line(frame,(0,170),(300,170),(200,200,0),2)

还有质心:

if w > 20 and h > 25: 
    cv2.rectangle(frame, (x,y), (x+w,y+h), (180, 1, 0), 1)

    x1=w/2      
    y1=h/2
    cx=x+x1
    cy=y+y1
    centroid=(cx,cy)

    cv2.circle(frame,(int(cx),int(cy)),4,(0,255,0),-1)

我的计数代码:

 if cy==170:   
     counter=counter+1

任何人都可以帮助我.请.给您的建议谢谢！

Can anyone help me. please. for your advice thankyou!

推荐答案

这是我的方法，可以独立地处理视频帧频.假设您能够在每一帧跟踪汽车的质心，我将保存最后两个质心的位置(在我的代码中为last_centroid和centroid)，并按以下步骤进行处理:

Here is my approach that would work independently of the video frame rate. Assuming that you are able to track a car's centroid at each frame, I would save the last two centroids' position (last_centroid and centroid in my code) and process as follows:

1. 从 aX + bY + c = 0 )
2. 计算last_centroid和centroid之间的线段的方程的参数
3. 查找两行是否相交
4. 如果是这样，请增加您的计数器

1. compute the intercepting line equation's parameters ( (a,b,c) from aX + bY + c = 0)
2. compute the equation's parameters of the segment line between last_centroid and centroid
3. find if the two lines are intersecting
4. if so, increment your counter

这是我在OpenCV(Python)中实现它的方式:

Here is how I implemented it in OpenCV (Python):

import cv2
import numpy as np
import collections

Params = collections.namedtuple('Params', ['a','b','c']) #to store equation of a line

def calcParams(point1, point2): #line's equation Params computation
    if point2[1] - point1[1] == 0:
         a = 0
         b = -1.0
    elif point2[0] - point1[0] == 0:
        a = -1.0
        b = 0
    else:
        a = (point2[1] - point1[1]) / (point2[0] - point1[0])
        b = -1.0

    c = (-a * point1[0]) - b * point1[1]
    return Params(a,b,c)

def areLinesIntersecting(params1, params2, point1, point2):
    det = params1.a * params2.b - params2.a * params1.b
    if det == 0:
        return False #lines are parallel
    else:
        x = (params2.b * -params1.c - params1.b * -params2.c)/det
        y = (params1.a * -params2.c - params2.a * -params1.c)/det
        if x <= max(point1[0],point2[0]) and x >= min(point1[0],point2[0]) and y <= max(point1[1],point2[1]) and y >= min(point1[1],point2[1]):
            print("intersecting in:", x,y)
            cv2.circle(frame,(int(x),int(y)),4,(0,0,255), -1) #intersecting point
            return True #lines are intersecting inside the line segment
        else:
            return False #lines are intersecting but outside of the line segment

cv2.namedWindow('frame')
frame = np.zeros((240,320,3), np.uint8)

last_centroid = (200,200) #centroid of a car at t-1
centroid = (210,180) #centroid of a car at t

line_params = calcParams(last_centroid, centroid)
intercept_line_params = calcParams((0,170), (300,170))
print("Params:", line_params.a,line_params.b,line_params.c) 

while(1):
    cv2.circle(frame,last_centroid,4,(0,255,0), -1) #last_centroid
    cv2.circle(frame,centroid,4,(0,255,0), -1) #current centroid
    cv2.line(frame,last_centroid,centroid,(0,0,255),1) #segment line between car centroid at t-1 and t
    cv2.line(frame,(0,170),(300,170),(200,200,0),2) #intercepting line
    print("AreLinesIntersecting: ",areLinesIntersecting(intercept_line_params,line_params,last_centroid,centroid)) 
    cv2.imshow('frame',frame)
    if cv2.waitKey(15) & 0xFF == ord('q'):
        break

cv2.destroyAllWindows()

这是一些结果:

图1.线段与线相交(蓝色中的线段-红色中的last_centroid和centroid之间的线段)


图2.段与线不相交

Fig1. Segment is intersecting the line (intercepting line in blue - segment line between last_centroid and centroid in red)


Fig2. Segment is NOT intersecting the line

NB 我找到了计算交点的公式

N.B. I found the formulas to calculate the intersection point here.

我希望我的方法将有助于解决您的问题.

I hope my approach will help to address your problem.

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