import cv2
import numpy as np


def get_bounding_box(image_input):
    """
    从阈值化图像中提取最小外接矩形，返回四个角点坐标（顺时针）
    
    参数
    ----
    image_input : 图像文件路径或图像数组
    """
    if isinstance(image_input, str):
        # 如果是文件路径
        image = cv2.imread(image_input, cv2.IMREAD_GRAYSCALE)
        if image is None:
            raise FileNotFoundError(f"图像文件 {image_input} 未找到")
    else:
        # 如果是图像数组
        image = cv2.cvtColor(image_input, cv2.COLOR_BGR2GRAY) if image_input.ndim == 3 else image_input.copy()

    coords = np.argwhere(image > 0)
    if coords.size == 0:
        raise ValueError("图像中没有非零像素，无法计算外接矩形")

    ymin, xmin = coords.min(axis=0)
    ymax, xmax = coords.max(axis=0)

    # 返回四个角点（顺时针）
    return (xmin, ymin), (xmax, ymin), (xmax, ymax), (xmin, ymax)


def get_line_equation(p1, p2):
    """
    给定两点 (p1, p2)，返回直线方程：
    - 垂直线: (None, x_const, y1, y2)
    - 水平线: (0, y_const, x1, x2)
    - 斜率线: (a, b, x1, x2) 对应 y = ax + b，范围 [x1, x2]
    """
    if p2[0] == p1[0]:  # 垂直线
        return None, p1[0], p1[1], p2[1]
    elif p2[1] == p1[1]:  # 水平线
        return 0, p1[1], p1[0], p2[0]
    else:
        a = (p2[1] - p1[1]) / (p2[0] - p1[0])
        b = p1[1] - a * p1[0]
        return a, b, p1[0], p2[0]

def calculate_lines(top_left, top_right, bottom_right, bottom_left):
    """
    返回外接矩形四条边的线性表达式
    """
    top_line = get_line_equation(top_left, top_right)
    right_line = get_line_equation(top_right, bottom_right)
    bottom_line = get_line_equation(bottom_right, bottom_left)
    left_line = get_line_equation(bottom_left, top_left)
    return top_line, right_line, bottom_line, left_line

def apply_morphology(gray,
                     kernel_size=(5, 5),
                     erode_iter=3,
                     dilate_iter=3):
    """
    对灰度图执行"腐蚀 → 膨胀"去噪声并返回处理后的结果。

    参数
    ----
    gray         : np.ndarray，灰度图 (H, W)
    kernel_size  : structuring element 尺寸
    erode_iter   : 腐蚀迭代次数
    dilate_iter  : 膨胀迭代次数
    """
    kernel = cv2.getStructuringElement(cv2.MORPH_RECT, kernel_size)
    out = cv2.erode(gray, kernel, iterations=erode_iter)
    out = cv2.dilate(out, kernel, iterations=dilate_iter)
    return out


def perpendicular_foot(pt, line_info):
    """
    计算点 pt 到指定直线 line_info 的垂足坐标。
    pt        : (x0, y0)
    line_info : get_line_equation() 的返回值
    """
    x0, y0 = pt

    if line_info[0] is None:                 # 垂直线 x = const
        return int(line_info[1]), int(y0)

    if line_info[0] == 0:                    # 水平线 y = const
        return int(x0), int(line_info[1])

    a, b, *_ = line_info                     # 斜率线 y = ax + b
    xf = (x0 + a * (y0 - b)) / (1 + a**2)
    yf = a * xf + b
    return int(round(xf)), int(round(yf))