import cv2

# 全局变量
refPt = []
drawing = False


def draw_line(event, x, y, flags, param):
    global refPt, drawing, image

    # 鼠标左键按下时，记录起始点坐标并开始绘制
    if event == cv2.EVENT_LBUTTONDOWN:
        refPt = [(x, y)]
        drawing = True

    # 当鼠标移动且处于绘制状态时，更新图像以显示当前的线段
    elif event == cv2.EVENT_MOUSEMOVE and drawing:
        temp_image = image.copy()
        cv2.line(temp_image, refPt[0], (x, y), (0, 255, 0), 2)
        cv2.imshow("Image", temp_image)

    # 鼠标左键释放时，记录终点坐标，结束绘制并计算线段长度
    elif event == cv2.EVENT_LBUTTONUP:
        refPt.append((x, y))
        drawing = False
        # 在图像上画线
        cv2.line(image, refPt[0], refPt[1], (0, 255, 0), 2)
        cv2.imshow("Image", image)

        # 计算线段长度
        dx = refPt[1][0] - refPt[0][0]
        dy = refPt[1][1] - refPt[0][1]
        length = (dx ** 2 + dy ** 2) ** 0.5
        print(f"线段长度: {length:.2f} 像素")


# 加载图像
image_path = 'your_image_path_here.jpg'  # 替换为你的图像路径
image = cv2.imread(image_path)
cv2.namedWindow("Image")
cv2.setMouseCallback("Image", draw_line)

while True:
    cv2.imshow("Image", image)
    key = cv2.waitKey(1) & 0xFF

    # 按下 'q' 键退出循环
    if key == ord('q'):
        break

cv2.destroyAllWindows()