写一个mfc的逐边裁剪算法

逐边裁剪算法（也称为Cohen-Sutherland算法）是一种经典的线段裁剪算法，用于将线段裁剪为视口或窗口的可见部分。下面是一个简单的MFC逐边裁剪算法的示例：

// 定义裁剪窗口的边界
#define LEFT_EDGE   0x01
#define RIGHT_EDGE  0x02
#define BOTTOM_EDGE 0x04
#define TOP_EDGE    0x08

// 定义线段的端点类
class CPoint2D
{
public:
    int x;
    int y;
};

// 定义逐边裁剪算法类
class CClipper
{
public:
    CClipper(CPoint2D winMin, CPoint2D winMax);
    void ClipLine(CPoint2D& p1, CPoint2D& p2);

private:
    void ComputeOutCode(CPoint2D& p, int& code);
    bool ClipTest(double p, double q, double& u1, double& u2);
    void ClipLeft(CPoint2D& p1, CPoint2D& p2);
    void ClipRight(CPoint2D& p1, CPoint2D& p2);
    void ClipBottom(CPoint2D& p1, CPoint2D& p2);
    void ClipTop(CPoint2D& p1, CPoint2D& p2);

    CPoint2D m_winMin;
    CPoint2D m_winMax;
};

// 构造函数：初始化裁剪窗口的边界
CClipper::CClipper(CPoint2D winMin, CPoint2D winMax)
{
    m_winMin = winMin;
    m_winMax = winMax;
}

// 逐边裁剪算法
void CClipper::ClipLine(CPoint2D& p1, CPoint2D& p2)
{
    // 计算p1和p2的编码
    int code1 = 0, code2 = 0;
    ComputeOutCode(p1, code1);
    ComputeOutCode(p2, code2);

    // 如果线段在裁剪窗口内，则不需要裁剪
    while (code1 | code2)
    {
        // 如果线段完全在裁剪窗口外，则直接退出
        if (code1 & code2)
            return;

        // 计算需要裁剪的边界
        double u1 = 0.0, u2 = 0.0;
        if (code1)
            ClipTest(p2.x - p1.x, p1.x - m_winMin.x, u1, u2) || ClipTest(p2.y - p1.y, p1.y - m_winMin.y, u1, u2);
        else
            ClipTest(p2.x - p1.x, m_winMax.x - p1.x, u1, u2) || ClipTest(p2.y - p1.y, m_winMax.y - p1.y, u1, u2);

        // 根据需要裁剪的边界进行裁剪
        if (code1 & LEFT_EDGE)
            ClipLeft(p1, p2);
        else if (code1 & RIGHT_EDGE)
            ClipRight(p1, p2);
        else if (code1 & BOTTOM_EDGE)
            ClipBottom(p1, p2);
        else if (code1 & TOP_EDGE)
            ClipTop(p1, p2);

        // 更新编码
        ComputeOutCode(p1, code1);
        ComputeOutCode(p2, code2);
    }
}

// 计算点的编码
void CClipper::ComputeOutCode(CPoint2D& p, int& code)
{
    code = 0;
    if (p.x < m_winMin.x)
        code |= LEFT_EDGE;
    else if (p.x > m_winMax.x)
        code |= RIGHT_EDGE;
    if (p.y < m_winMin.y)
        code |= BOTTOM_EDGE;
    else if (p.y > m_winMax.y)
        code |= TOP_EDGE;
}

// 计算需要裁剪的边界
bool CClipper::ClipTest(double p, double q, double& u1, double& u2)
{
    double r = q / p;
    if (p < 0.0)
    {
        if (r > u1)
            u1 = r;
        if (r > u2)
            return true;
    }
    else if (p > 0.0)
    {
        if (r < u2)
            u2 = r;
        if (r < u1)
            return true;
    }
    else if (q < 0.0)
        return true;

    return false;
}

// 裁剪左边界
void CClipper::ClipLeft(CPoint2D& p1, CPoint2D& p2)
{
    double u = (double)(m_winMin.x - p1.x) / (double)(p2.x - p1.x);
    p1.y = (int)(p1.y + u * (p2.y - p1.y));
    p1.x = m_winMin.x;
}

// 裁剪右边界
void CClipper::ClipRight(CPoint2D& p1, CPoint2D& p2)
{
    double u = (double)(m_winMax.x - p1.x) / (double)(p2.x - p1.x);
    p1.y = (int)(p1.y + u * (p2.y - p1.y));
    p1.x = m_winMax.x;
}

// 裁剪下边界
void CClipper::ClipBottom(CPoint2D& p1, CPoint2D& p2)
{
    double u = (double)(m_winMin.y - p1.y) / (double)(p2.y - p1.y);
    p1.x = (int)(p1.x + u * (p2.x - p1.x));
    p1.y = m_winMin.y;
}

// 裁剪上边界
void CClipper::ClipTop(CPoint2D& p1, CPoint2D& p2)
{
    double u = (double)(m_winMax.y - p1.y) / (double)(p2.y - p1.y);
    p1.x = (int)(p1.x + u * (p2.x - p1.x));
    p1.y = m_winMax.y;
}

在上面的示例中，我们首先定义了一个CPoint2D类来表示线段的端点。然后，我们定义了一个CClipper类来实现逐边裁剪算法。该类的构造函数用于初始化裁剪窗口的边界，ClipLine()函数用于裁剪线段。该算法使用了Cohen-Sutherland编码方法来计算线段的编码，并根据编码计算需要裁剪的边界。ClipTest()函数用于计算需要裁剪的边界，而ClipLeft()、ClipRight()、ClipBottom()和ClipTop()函数用于实现裁剪操作。