写一个mfc的sutherland-hodgman算法

以下是一个简单的 MFC 实现 Sutherland-Hodgman 算法的代码：

// 定义多边形的点数
#define POLYGON_SIZE 4

// 定义两个点的结构体
struct Point {
    float x;
    float y;
};

// 定义多边形的结构体
struct Polygon {
    Point points[POLYGON_SIZE];
};

// Sutherland-Hodgman 算法
Polygon clipPolygon(Polygon subjectPolygon, Polygon clipPolygon) {
    Polygon outputPolygon = subjectPolygon;

    // 依次遍历裁剪多边形的边
    for (int i = 0; i < POLYGON_SIZE; i++) {
        Point clipStart = clipPolygon.points[i];
        Point clipEnd = clipPolygon.points[(i + 1) % POLYGON_SIZE];

        Polygon inputPolygon = outputPolygon;
        outputPolygon = {};

        // 依次遍历多边形的边
        for (int j = 0; j < POLYGON_SIZE; j++) {
            Point subjectStart = inputPolygon.points[j];
            Point subjectEnd = inputPolygon.points[(j + 1) % POLYGON_SIZE];

            float startLocation = (clipEnd.x - clipStart.x) * (subjectStart.y - clipStart.y) - (clipEnd.y - clipStart.y) * (subjectStart.x - clipStart.x);
            float endLocation = (clipEnd.x - clipStart.x) * (subjectEnd.y - clipStart.y) - (clipEnd.y - clipStart.y) * (subjectEnd.x - clipStart.x);

            // 判断起点位置
            if (startLocation >= 0) {
                outputPolygon.points[outputPolygonSize++] = subjectStart;
            }

            // 判断起点和终点位置
            if (startLocation * endLocation < 0) {
                float intersectionX = (clipEnd.x - clipStart.x) * (subjectStart.y - clipStart.y) - (clipEnd.y - clipStart.y) * (subjectStart.x - clipStart.x);
                float intersectionY = (clipEnd.y - clipStart.y) * (subjectEnd.x - clipStart.x) - (clipEnd.x - clipStart.x) * (subjectEnd.y - clipStart.y);

                intersectionX /= (subjectEnd.y - subjectStart.y) * (clipEnd.x - clipStart.x) - (subjectEnd.x - subjectStart.x) * (clipEnd.y - clipStart.y);
                intersectionY /= (subjectEnd.y - subjectStart.y) * (clipEnd.x - clipStart.x) - (subjectEnd.x - subjectStart.x) * (clipEnd.y - clipStart.y);

                Point intersection = { intersectionX, intersectionY };
                outputPolygon.points[outputPolygonSize++] = intersection;
            }
        }
    }

    return outputPolygon;
}

// 绘制多边形
void drawPolygon(CDC* pDC, Polygon polygon) {
    CPoint points[POLYGON_SIZE];
    for (int i = 0; i < POLYGON_SIZE; i++) {
        points[i] = CPoint(polygon.points[i].x, polygon.points[i].y);
    }
    pDC->Polygon(points, POLYGON_SIZE);
}

// 绘制裁剪框
void drawClipRectangle(CDC* pDC, Polygon clipPolygon) {
    CPoint points[POLYGON_SIZE];
    for (int i = 0; i < POLYGON_SIZE; i++) {
        points[i] = CPoint(clipPolygon.points[i].x, clipPolygon.points[i].y);
    }
    pDC->Polyline(points, POLYGON_SIZE);
}

// 绘制函数
void CMyView::OnDraw(CDC* pDC)
{
    CMyDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);

    // 定义多边形和裁剪框
    Polygon subjectPolygon = { { { 100, 100 }, { 200, 100 }, { 200, 200 }, { 100, 200 } } };
    Polygon clipPolygon = { { { 150, 150 }, { 250, 150 }, { 250, 250 }, { 150, 250 } } };

    // 绘制多边形和裁剪框
    drawPolygon(pDC, subjectPolygon);
    drawClipRectangle(pDC, clipPolygon);

    // 裁剪多边形
    Polygon outputPolygon = clipPolygon(subjectPolygon, clipPolygon);

    // 绘制裁剪后的多边形
    drawPolygon(pDC, outputPolygon);
}

在该代码中，我们定义了结构体 Point 和 Polygon 表示点和多边形，clipPolygon 函数接收两个多边形作为参数，返回裁剪后的多边形。我们使用 MFC 的 CDC 绘制多边形和裁剪框，并使用 drawPolygon 函数绘制多边形，使用 drawClipRectangle 函数绘制裁剪框。最后，在 OnDraw 函数中调用 clipPolygon 函数对多边形进行裁剪，并使用 drawPolygon 函数绘制裁剪后的多边形。