引用图形库头文件的Sutherland-Hodgman逐边裁剪c++算法

以下是使用图形库头文件的Sutherland-Hodgman逐边裁剪c算法的示例代码：

#include <graphics.h>
#include <stdlib.h>

//定义裁剪窗口的四个顶点坐标
#define LEFT_EDGE   100
#define RIGHT_EDGE  500
#define TOP_EDGE    100
#define BOTTOM_EDGE 400

//定义多边形顶点个数
#define N 4

//定义多边形顶点坐标
int poly[2*N] = { 250, 50, 450, 250, 250, 450, 50, 250 };

//定义裁剪后的多边形顶点坐标
int clipped_poly[2*N];

//定义辅助函数，判断点是否在裁剪窗口内
int inside(int x, int y) {
    if (x >= LEFT_EDGE && x <= RIGHT_EDGE && y >= TOP_EDGE && y <= BOTTOM_EDGE) {
        return 1;
    } else {
        return 0;
    }
}

//定义辅助函数，计算交点
void intersect(int x1, int y1, int x2, int y2, int *xi, int *yi) {
    float m = (float)(y2 - y1) / (float)(x2 - x1);
    float b = (float)y1 - m * (float)x1;
    if (x1 == x2) {
        *xi = x1;
        *yi = (int)(m * (float)x1 + b);
    } else if (y1 == y2) {
        *xi = (int)((float)(y1 - b) / m);
        *yi = y1;
    } else {
        *xi = (int)((float)(TOP_EDGE - b) / m);
        *yi = TOP_EDGE;
        if (*xi < LEFT_EDGE || *xi > RIGHT_EDGE) {
            *xi = (int)((float)(BOTTOM_EDGE - b) / m);
            *yi = BOTTOM_EDGE;
        }
    }
}

//定义Sutherland-Hodgman算法
void sutherland_hodgman() {
    int i, j, k, xi, yi;
    int lastx = poly[2*N-2], lasty = poly[2*N-1];
    for (i = 0; i < N; i++) {
        int x = poly[2*i], y = poly[2*i+1];
        j = 0;
        for (k = 0; k < j; k++) {
            if (inside(x, y)) {
                if (!inside(lastx, lasty)) {
                    intersect(x, y, lastx, lasty, &xi, &yi);
                    clipped_poly[2*j] = xi;
                    clipped_poly[2*j+1] = yi;
                    j++;
                }
                clipped_poly[2*j] = x;
                clipped_poly[2*j+1] = y;
                j++;
            } else if (inside(lastx, lasty)) {
                intersect(x, y, lastx, lasty, &xi, &yi);
                clipped_poly[2*j] = xi;
                clipped_poly[2*j+1] = yi;
                j++;
            }
            lastx = x;
            lasty = y;
        }
        if (inside(x, y)) {
            if (!inside(lastx, lasty)) {
                intersect(x, y, lastx, lasty, &xi, &yi);
                clipped_poly[2*j] = xi;
                clipped_poly[2*j+1] = yi;
                j++;
            }
            clipped_poly[2*j] = x;
            clipped_poly[2*j+1] = y;
            j++;
        } else if (inside(lastx, lasty)) {
            intersect(x, y, lastx, lasty, &xi, &yi);
            clipped_poly[2*j] = xi;
            clipped_poly[2*j+1] = yi;
            j++;
        }
        lastx = x;
        lasty = y;
    }
}

//主函数
int main() {
    int gd = DETECT, gm;
    initgraph(&gd, &gm, "");
    setcolor(YELLOW);
    rectangle(LEFT_EDGE, TOP_EDGE, RIGHT_EDGE, BOTTOM_EDGE);
    setcolor(BLUE);
    fillpoly(N, poly);
    getch();
    sutherland_hodgman();
    cleardevice();
    setcolor(YELLOW);
    rectangle(LEFT_EDGE, TOP_EDGE, RIGHT_EDGE, BOTTOM_EDGE);
    setcolor(BLUE);
    fillpoly(N, clipped_poly);
    getch();
    closegraph();
    return 0;
}

该算法首先定义了裁剪窗口的四个顶点坐标和多边形顶点坐标，然后定义了一个辅助函数`inside`，用于判断点是否在裁剪窗口内，以及一个辅助函数`intersect`，用于计算交点。接下来是Sutherland-Hodgman算法的主要部分，其中使用了循环依次处理多边形的每一条边，对于每条边，算法通过判断该边的两个端点是否在裁剪窗口内，从而确定需要保留的点。对于不在裁剪窗口内的点，算法通过计算交点从而得到裁剪后的多边形顶点坐标。最后，算法使用`fillpoly`函数绘制裁剪前后的多边形。