如何在 Opencv Python 中查找特定地标点的坐标

Question

我想获取物体移动的移动地标点的坐标。 我试着先检测选择一个点。 我是 OpenCV 和 python 的初学者。 不知道有没有函数。

import cvzone
import numpy as np
from cvzone.FaceMeshModule import FaceMeshDetector
from cvzone.PlotModule import LivePlot



idList = [8]
 
cap = cv2.VideoCapture(0)
detector = FaceMeshDetector(maxFaces=1)


while True:
 
    if cap.get(cv2.CAP_PROP_POS_FRAMES) == cap.get(cv2.CAP_PROP_FRAME_COUNT):
        cap.set(cv2.CAP_PROP_POS_FRAMES, 0)
 
    success, img = cap.read()
    img, faces = detector.findFaceMesh(img, draw = False)
    
    if faces:
        face = faces[0]
        leftUp = face[8]
        
        for id in idList:
            cv2.circle(img, face[id], 3,(80,200,120), cv2.FILLED)

    
    img = cv2.resize(img,(640,360))
    cv2.imshow("image", img)
    cv2.waitKey(25)
         
cap.release()
cv2.destroyAllWindows()

Answer 1

如果我对这个问题的理解是正确的，那么您想检测地标中是否有特定点在移动。

为此，我建议首先确定地标的索引，我找不到具体的文档，但您可以使用以下代码来识别它：

import cv2
from cvzone.FaceMeshModule import FaceMeshDetector

cap = cv2.VideoCapture(0)
detector = FaceMeshDetector(maxFaces=1)

def click_event(event, x, y, faces, detector):
        if event == cv2.EVENT_LBUTTONDOWN and faces[0]:
            lstOfPoints = [detector.findDistance(faces[0][i], (x, y))[0] for i in range(0, 468)]
            print(lstOfPoints.index(min(lstOfPoints)))

while True:
        _, img = cap.read()
        img, faces = detector.findFaceMesh(img, draw=False)
        if faces:
            face = faces[0]
            for i in range(0, 468):
                    cv2.circle(img, (face[i][0], face[i][1]), 1, (0, 255, 0), cv2.FILLED)
            cv2.imshow("Image", img)
            cv2.setMouseCallback('Image', lambda event, x , y, flags, params :click_event(event, x, y, faces, detector))
            cv2.waitKey(1)
        else:
            cv2.imshow("Image", img)
            cv2.waitKey(1)

您可以单击要打印其索引的要标识的点。

一旦找到要查找的点，就可以像这样更改代码：

import cv2
from cvzone.FaceMeshModule import FaceMeshDetector
import math
cap = cv2.VideoCapture(0)
detector = FaceMeshDetector(maxFaces=1)
idxOfPoint = 50
i = 10
while True:
        _, img = cap.read()
        img, faces = detector.findFaceMesh(img, draw=False)
        if faces:
            if i != 10 and i % 30 == 0:
                distanceChange = math.sqrt((faces[0][idxOfPoint][0] - pastCoord[0])**2 + (faces[0][idxOfPoint][1] - pastCoord[1])**2)
                print("point moved" if distanceChange > 20 else "point didn't move")
                pastCoord  = faces[0][idxOfPoint]
            if i == 10:
                pastCoord  = faces[0][idxOfPoint]
            cv2.circle(img, (faces[0][idxOfPoint][0], faces[0][idxOfPoint][1]), 1, (0, 255, 0), cv2.FILLED) 
            cv2.imshow("Image", img)
            cv2.waitKey(1)
            i += 1
        else:
            cv2.imshow("Image", img)
            cv2.waitKey(1)

其中 30（在i % 30中）表示每帧验证的频率，20（在distanceChange > 20中）表示触发打印的最小距离变化。