C++ 时钟；多角星；花环实现。

最近在回顾C++，写了几个小玩意儿练习一下，该找工作了，十分焦虑。

好了，开始正文

首先如何画多角星？比如五角星，六角星等等？

这里以五角星为例，r1需要被指定，r2可以通过正弦定理得到。然后通过每一步增加360/2n的角度，依次通过短半径和长半径循环计算每个顶点的坐标。如果需要绘制的图形堆成，那么仅需计算一半，另一半通过对称得出。直接贴代码：

void InitNStar(int n, int x, int y, float radius, float offest) {
    POINT* pts = new POINT[n * 2];
    float angle_A = 360.0 / n;
    float angle_D = 180.0 - 90.0 * (n - 2) / n;

    float angle_E = 180.0 - angle_D - angle_A / 2.0;
    float short_radius = radius / sinf(to_radian(angle_D)) * sinf(to_radian(angle_E));
    float rs[] = {radius,short_radius};
    for (int i = 0; i < 2*n; i++) {
        int sx = cosf(to_radian(270.0 + i * angle_A / 2.0 + offest)) * rs[i % 2] + 0.5;
        int sy = sinf(to_radian(270.0 + i * angle_A / 2.0 + offest)) * rs[i % 2] + 0.5;
        pts[i].x = sx+x;
        pts[i].y = sy+y;
    }
    solidpolygon(pts, n * 2);
}

 同理，对于花环的绘制依然可以参考这个思路。

如果不需要考虑每个小圆的弧度，直接绘制圆即可。

void DrawFlower(int n, int radius, int angle_C, int offest_x=0, int offest_y=0) {

    float angle_A = 2 * PI / n;
    float small_radius = radius * sinf(angle_A / 2) / sinf(to_radian(angle_C) / 2);
    float mid_radius = radius * sinf((2 * PI - to_radian(angle_C) - angle_A) / 2) / sinf(to_radian(angle_C) / 2);
    int x, y = 0;
    for (int i = 0; i < n; i++) {
        x = cosf(PI * 3 / 2 + angle_A * i) * mid_radius + 0.5;
        y = sinf(PI * 3 / 2 + angle_A * i) * mid_radius + 0.5;
        setfillcolor(RGB(253, 91 + i * (80 / n), 120 + i * (80 / n)));
        solidcircle(x + offest_x, y + offest_y, small_radius);
    }
}

然后加一点细节让他动起来：

#include <iostream>
#include <cmath>
#include <graphics.h>
#include <Windows.h>

#define PI 3.1415926

using namespace std;

float to_radian(float a) {
    return a * 3.1415926 / 180.0;
}

void DrawFlower(int n, int radius, int angle_C, int offest_x=0, int offest_y=0, int R=255,int G=91,int B=120, bool gradual=true, float offest_ang= PI * 3 / 2) {

    float angle_A = 2 * PI / n;
    float small_radius = radius * sinf(angle_A / 2) / sinf(to_radian(angle_C) / 2);
    float mid_radius = radius * sinf((2 * PI - to_radian(angle_C) - angle_A) / 2) / sinf(to_radian(angle_C) / 2);
    int x, y, x1, y1, x2, y2 = 0;
    for (int i = 0; i < n; i++) {
        x = cosf(offest_ang + angle_A * i) * mid_radius + 0.5 + offest_x;
        y = sinf(offest_ang + angle_A * i) * mid_radius + 0.5 + offest_y;
        if (gradual)
            setfillcolor(RGB(R, G + i * (80 / n), B + i * (80 / n)));
        else
            setfillcolor(RGB(R, G, B));
        /*solidcircle(x + offest_x, y + offest_y, small_radius);*/
        float ang = offest_ang + PI  - to_radian(angle_C) / 2.0 + i * angle_A;
        solidpie(x - small_radius, y - small_radius, x + small_radius, y + small_radius, -ang, -ang - to_radian(angle_C));
        x1 = cosf(offest_ang + angle_A * i - angle_A * 0.5) * (radius + 2) + 0.5 + offest_x;
        y1 = sinf(offest_ang + angle_A * i - angle_A * 0.5) * (radius + 2) + 0.5 + offest_y;
        x2 = cosf(offest_ang + angle_A * (i + 1) - angle_A * 0.5) * (radius + 2) + 0.5 + offest_x;
        y2 = sinf(offest_ang + angle_A * (i + 1) - angle_A * 0.5) * (radius + 2) + 0.5 + offest_y;
        POINT pts[4] = { {x1,y1},{x,y},{x2,y2} ,{0+offest_x,0+offest_y} };
        solidpolygon(pts, 4);
    }
}

int main() {

    initgraph(800, 1000);

    setorigin(400, 400);

    setbkcolor(RGB(135, 206, 235));
    cleardevice();
    int n = 8, i = 0;

    while (1) {
        cleardevice();
        BeginBatchDraw();
        int x = sinf(PI * i / 400) * 50;
        int y = sinf(PI * i / 400) * 10;
        POINT pts[4] = { {x,y},{100,200},{-100,400},{0,600} };
        setlinestyle(PS_SOLID | PS_ENDCAP_ROUND, 16);
        setlinecolor(RGB(0, 120, 80));
        polybezier(pts, 4);
        DrawFlower(8, 150, 120, x+3, y+3, 220, 220, 220, false, PI * i++ / 400);
        DrawFlower(8, 150, 120, x, y, 255, 92, 120, true, PI * i++ / 400);
        setfillcolor(RGB(238, 232, 171));
        solidcircle(x, y, 30);
        FlushBatchDraw();
        if (i > 800)
            i = 0;
        Sleep(10);
    }

    getchar();
    return 0;
}

 如何画时钟？

获取时分秒之后，通过时分秒的值得到指针角度，每个循环进行更新。

        time_t nowtime;
    time(&nowtime); 
    tm p;
    localtime_s(&p, &nowtime); 

    int hour = p.tm_hour;
    int minute = p.tm_min;
    int second = p.tm_sec;
    int x1, y1, x2, y2 = 0;

    // 时针
    setlinecolor(RGB(23,124,80));
    setlinestyle(PS_SOLID | PS_ENDCAP_ROUND, 16);
    x1 = int(cosf(to_radian(90 + hour * 30)) * 30 + 0.5);
    y1 = int(sinf(to_radian(90 + hour * 30)) * 30 + 0.5);
    x2 = int(cosf(to_radian(270 + hour * 30)) * 150 + 0.5);
    y2 = int(sinf(to_radian(270 + hour * 30)) * 150 + 0.5);
    line(x1, y1, x2, y2);
    //solidroundrect(-30, -8, 200, 8, 20, 10);

    //分针
    setlinecolor(RGB(23, 124, 180));
    setlinestyle(PS_SOLID | PS_ENDCAP_ROUND, 12);
    x1 = int(cosf(to_radian(90 + minute * 6)) * 35 + 0.5);
    y1 = int(sinf(to_radian(90 + minute * 6)) * 35 + 0.5);
    x2 = int(cosf(to_radian(270 + minute * 6)) * 165 + 0.5);
    y2 = int(sinf(to_radian(270 + minute * 6)) * 165 + 0.5);
    line(x1, y1, x2, y2);
    
    //秒针
    setlinecolor(BLACK);
    setlinestyle(PS_SOLID | PS_ENDCAP_ROUND, 8);
    x1 = int(cosf(to_radian(90 + second * 6)) * 40 + 0.5);
    y1 = int(sinf(to_radian(90 + second * 6)) * 40 + 0.5);
    x2 = int(cosf(to_radian(270 + second * 6)) * 180 +0.5);
    y2 = int(sinf(to_radian(270 + second * 6)) * 180 +0.5);
    line(x1, y1, x2, y2);

    setfillcolor(RGB(123, 34, 80));
    solidcircle(0, 0, 15);

最后的代码在这里：来往/EasyX_Clock (gitee.com)