用easyx画五角星

### 如何使用EasyX图形库绘制五角星

为了实现五角星的绘制，可以利用EasyX图形库提供的绘图功能。下面是一个完整的C++程序示例，展示了如何通过计算五个顶点的位置来画出一个正五角星。

#include <graphics.h>
#include <math.h>

void DrawFivePointedStar(int centerX, int centerY, int outerRadius) {
    const double PI = 3.1415926;
    const int numPoints = 5; // Five points of the star
    
    POINT points[numPoints * 2]; // For alternating inner and outer points

    for (int i = 0; i < numPoints; ++i) {
        // Calculate angle between each point
        float theta = ((float)i / numPoints + 0.5f) * 2.0f * PI;

        // Outer vertex calculation
        points[i * 2].x = static_cast<int>(centerX + cos(theta) * outerRadius);
        points[i * 2].y = static_cast<int>(centerY - sin(theta) * outerRadius);

        // Inner vertices are calculated by shifting index forward one position with modulo operation.
        int nextIndex = (i + 2) % numPoints;
        float innerTheta = ((float)nextIndex / numPoints + 0.5f) * 2.0f * PI;
        
        // Assuming an approximate ratio for simplicity here as half radius for inner circle
        float innerRadius = outerRadius / 2.7f;
        points[(i * 2) + 1].x = static_cast<int>(centerX + cos(innerTheta) * innerRadius);
        points[(i * 2) + 1].y = static_cast<int>(centerY - sin(innerTheta) * innerRadius);
    }

    setlinecolor(RGB(255, 0, 0)); // Set line color to red
    polygon(points, sizeof(points)/sizeof(points[0])); // Draw filled or outlined based on your need
}

int main() {
    initgraph(800, 600); // Initialize graphic window size
    DrawFivePointedStar(400, 300, 150); // Call function to draw a five-pointed star at center location
    getchar(); // Wait until user presses any key before closing the graph window
    closegraph();
}

这段代码定义了一个`DrawFivePointedStar()`函数用于创建并连接构成五角星形状的一系列坐标点，并调用了EasyX库中的`polygon()`方法完成实际的绘画工作[^1]。