中心法画椭圆（各种大小位置）

最新推荐文章于 2021-05-24 02:59:37 发布

hnu_zxc

最新推荐文章于 2021-05-24 02:59:37 发布

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分类专栏：图形图像文章标签： float include user

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本文介绍了一种使用C++绘制椭圆的方法，并实现了椭圆绕中心点逆时针旋转的功能。通过调用特定的函数实现椭圆的绘制和旋转，展示了在图形界面中灵活操作图形的基本步骤。

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#include <winbgim.h>
#include <conio2.h>
#include <cmath>

void ellipseMP(int xcenter,int ycenter,int rx,int ry,float alpha);//alpha :椭圆绕中心点逆时针旋转的角度 (单位：弧度)
void ellipsePoints(int xcenter,int ycenter,int xpt,int ypt,float alpha);

int main()
{
     initwindow(640,480); //open a 640x480 graphics window

    ellipseMP(320,240,70,30,2.1);
     getch();   //wait for user to press a key
     closegraph();        //close graphics window
     return 0;
}


void ellipseMP(int xcenter,int ycenter,int rx,int ry,float alpha)
{
     int x2 = rx * rx,y2 = ry * ry;
     int x = 0,y = ry,p;
     int px = 0,py = 2 * x2 * y;
    
     ellipsePoints(xcenter,ycenter,x,y,alpha);
    
     /*region1*/
     p = y2 - x2 * ry + 0.25 * x2 + 0.5;
     while(px < py)
     {
              x++;
              px += 2 * y2;
             
              if(p < 0)
                   p += y2 + px;//or: p += y2 + 2 * y2 * x;
              else
                  {
                        y--;
                        py -= 2 * x2;
                        p += px + y2 - py;
                  }
             
              ellipsePoints(xcenter,ycenter,x,y,alpha);
     }
    
     /*region2*/
     p = y2 * (x + 0.5) * (x + 0.5) + x2 * (y - 1) * (y - 1) - x2 * y2 + 0.5;
     while(y > 0)
     {
              y--;
              py -= 2 * x2;
             
              if(p > 0)
                   p += x2 - py;
              else
                  {
                        x++;
                        px += 2 * y2;
                        p += px + x2 - py;
                  }
             
              ellipsePoints(xcenter,ycenter,x,y,alpha);
     }    
}

void ellipsePoints(int xcenter,int ycenter,int xpt,int ypt,float alpha)
{
     int x[4],y[4];
     //先旋转在四个象限的点 
     x[0] = xpt * cos(alpha) - ypt * sin(alpha);
     y[0] = xpt * sin(alpha) + ypt * cos(alpha);

     x[1] = -xpt * cos(alpha) + ypt * sin(alpha);
     y[1] = -xpt * sin(alpha) - ypt * cos(alpha);
    
     x[2] = xpt * cos(alpha) + ypt * sin(alpha);
     y[2] = xpt * sin(alpha) - ypt * cos(alpha);    

     x[3] = -xpt * cos(alpha) - ypt * sin(alpha);
     y[3] = -xpt * sin(alpha) + ypt * cos(alpha);    
    

     //输出四个点
     putpixel(xcenter + x[0],ycenter + y[0],RGB(255,0,0)); 
     putpixel(xcenter + x[1],ycenter + y[1],RGB(255,0,0)); 
     putpixel(xcenter + x[2],ycenter + y[2],RGB(255,0,0)); 
     putpixel(xcenter + x[3],ycenter + y[3],RGB(255,0,0));           
}