如何在Python中复刻Matlab的drawcircle交互式图像画圆功能？

完全可以在Python中借助Matplotlib或OpenCV实现交互式画圆并测量半径的功能，无需控制台迭代输入坐标。以下是两种实用方案：

方法一：使用Matplotlib实现交互式画圆 #

代码示例 #

import matplotlib.pyplot as plt
import numpy as np

class InteractiveCircleDrawer:
    def __init__(self, img):
        self.img = img
        self.fig, self.ax = plt.subplots()
        self.ax.imshow(img)
        self.circle = None
        self.center = None
        self.radius = 0

        # 绑定鼠标事件回调
        self.fig.canvas.mpl_connect('button_press_event', self.on_press)
        self.fig.canvas.mpl_connect('motion_notify_event', self.on_motion)
        self.fig.canvas.mpl_connect('button_release_event', self.on_release)

    def on_press(self, event):
        if event.button == 1:  # 左键点击确定圆心
            self.center = (event.xdata, event.ydata)
            self.circle = plt.Circle(self.center, 0, edgecolor='red', facecolor='none', linewidth=2)
            self.ax.add_patch(self.circle)

    def on_motion(self, event):
        if self.center is not None and event.inaxes == self.ax:
            # 实时计算并更新半径
            dx = event.xdata - self.center[0]
            dy = event.ydata - self.center[1]
            self.radius = np.sqrt(dx**2 + dy**2)
            self.circle.set_radius(self.radius)
            self.fig.canvas.draw()

    def on_release(self, event):
        if event.button == 1 and self.center is not None:
            # 标注半径数值
            self.ax.text(
                self.center[0], self.center[1]-self.radius-10, 
                f'Radius: {self.radius:.2f}', 
                color='white', fontsize=10, backgroundcolor='black'
            )
            self.center = None  # 重置状态，可继续绘制新圆
            self.fig.canvas.draw()

# 使用示例
if __name__ == '__main__':
    img = plt.imread('your_image_path.jpg')  # 替换为你的图像路径
    drawer = InteractiveCircleDrawer(img)
    plt.show()

操作方式 #

• 左键点击图像任意位置确定圆心
• 拖拽鼠标调整圆的半径，实时预览效果
• 松开左键完成绘制，自动显示半径数值
• 可重复操作绘制多个圆

方法二：使用OpenCV实现交互式画圆 #

代码示例 #

import cv2
import numpy as np

drawing = False  # 是否处于绘制状态
center = (-1, -1)
radius = 0

def draw_circle(event, x, y, flags, param):
    global drawing, center, radius, img_copy
    if event == cv2.EVENT_LBUTTONDOWN:
        drawing = True
        center = (x, y)
        radius = 0
    elif event == cv2.EVENT_MOUSEMOVE:
        if drawing:
            # 实时更新预览圆（每次复制原图避免轨迹残留）
            img_copy = img.copy()
            dx = x - center[0]
            dy = y - center[1]
            radius = int(np.sqrt(dx**2 + dy**2))
            cv2.circle(img_copy, center, radius, (0, 0, 255), 2)
    elif event == cv2.EVENT_LBUTTONUP:
        drawing = False
        # 绘制最终圆并标注半径
        cv2.circle(img_copy, center, radius, (0, 255, 0), 2)
        cv2.putText(
            img_copy, f'Radius: {radius}', 
            (center[0]-50, center[1]-radius-10), 
            cv2.FONT_HERSHEY_SIMPLEX, 0.5, (255, 255, 255), 1
        )

# 使用示例
if __name__ == '__main__':
    img = cv2.imread('your_image_path.jpg')  # 替换为你的图像路径
    img_copy = img.copy()
    cv2.namedWindow('Interactive Circle Drawer')
    cv2.setMouseCallback('Interactive Circle Drawer', draw_circle)

    while True:
        cv2.imshow('Interactive Circle Drawer', img_copy)
        key = cv2.waitKey(1) & 0xFF
        if key == 27:  # 按ESC键退出
            break
    cv2.destroyAllWindows()

操作方式 #

• 左键按下确定圆心
• 拖拽鼠标调整半径，实时显示红色预览圆
• 松开左键完成绘制，圆变为绿色并显示半径数值
• 按ESC键退出窗口

内容的提问来源于stack exchange，提问作者Rowland