写一段利用python语言，读取悬臂梁振动冲击视频，利用圆心标靶检测算法提取结构6个测点的位移并绘制每个测点的位移曲线的算法

下面是一个基于Python和OpenCV的算法，可以读取悬臂梁振动冲击视频，利用圆心标靶检测算法提取结构6个测点的位移并绘制每个测点的位移曲线。

1.首先，我们需要导入必要的库：

import cv2
import numpy as np
import matplotlib.pyplot as plt

2.读取视频文件并提取每一帧：

cap = cv2.VideoCapture('video.mp4')
frames = []
while True:
    ret, frame = cap.read()
    if not ret:
        break
    frames.append(frame)

3.定义圆心标靶检测函数，该函数接受一帧图像并返回所有检测到的圆心坐标：

def detect_circles(frame):
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    circles = cv2.HoughCircles(gray, cv2.HOUGH_GRADIENT, dp=1, minDist=20,
                               param1=50, param2=30, minRadius=5, maxRadius=30)
    if circles is not None:
        circles = np.round(circles[0, :]).astype("int")
    return circles

4.对每一帧进行圆心标靶检测，并提取6个测点的坐标：

points = []
for frame in frames:
    circles = detect_circles(frame)
    if circles is not None:
        for circle in circles:
            x, y, r = circle
            if r > 10:
                points.append((x, y))
    if len(points) == 6:
        break

5.对于每个测点，提取其在每一帧中的坐标，并计算其位移：

displacements = [[] for _ in range(6)]
for frame in frames:
    circles = detect_circles(frame)
    if circles is not None:
        for i, point in enumerate(points):
            min_dis = np.inf
            for circle in circles:
                x, y, _ = circle
                dis = np.sqrt((x - point[0]) ** 2 + (y - point[1]) ** 2)
                if dis < min_dis:
                    min_dis = dis
                    nearest_circle = circle
            _, _, r = nearest_circle
            if r > 10:
                displacements[i].append(r)
    else:
        for i in range(6):
            displacements[i].append(np.nan)

6.绘制每个测点的位移曲线：

fig, axs = plt.subplots(nrows=2, ncols=3, figsize=(15, 8))
for i, ax in enumerate(axs.flatten()):
    ax.plot(displacements[i])
    ax.set_title(f"Point {i+1}")
plt.tight_layout()
plt.show()

完整代码如下：