Breseham椭圆绘画算法演变出来的程序！
这个程序主要的思想来自Breseham算法，
演变的东西就是增加了旋转！
算法描述就不写了，敲打起来很累！
把程序罗列出来吧！
Mfc 代码如下：
////////////////////////////////////////////////////////////////////////////////////
//BreEllipse
//(xc,yc)----------椭圆中心
//fla,flb----------横轴和纵轴的半径
//double-----------旋转的角度
////////////////////////////////////////////////////////////////////////////////////
void BreEllipse(CDC *pDC,float xc ,float yc,float fla,float flb,double angle)
{
int i;
float a,b,x,y;
double dx,dy,di,aa,bb,sinA,cosA;
cosA=cos(angle);
sinA=sin(angle);
a=fla;
b=flb;
aa=a*a;
bb=b*b;
float flX[4],flY[4];
x=0;
y=b;
dx=0;
dy=2*aa*y;
di=bb-aa*b+aa/4;
flX[0]=xc+x*cosA-y*sinA;
flX[1]=xc+x*cosA+y*sinA;
flX[2]=xc-x*cosA-y*sinA;
flX[3]=xc-x*cosA+y*sinA;
flY[0]=yc+y*cosA+x*sinA;
flY[1]=yc-y*cosA+x*sinA;
flY[2]=yc+y*cosA-x*sinA;
flY[3]=yc-y*cosA-x*sinA;
i=0;
while(dx<dy)
{
i++;
if(i==5)
{
pDC->MoveTo(flX[0],flY[0]);
pDC->LineTo(xc+x*cosA-y*sinA,yc+y*cosA+x*sinA);
pDC->MoveTo(flX[1],flY[1]);
pDC->LineTo(xc+x*cosA+y*sinA,yc-y*cosA+x*sinA);
pDC->MoveTo(flX[2],flY[2]);
pDC->LineTo(xc-x*cosA-y*sinA,yc+y*cosA-x*sinA);
pDC->MoveTo(flX[3],flY[3]);
pDC->LineTo(xc-x*cosA+y*sinA,yc-y*cosA-x*sinA);
flX[0]=xc+x*cosA-y*sinA;
flX[1]=xc+x*cosA+y*sinA;
flX[2]=xc-x*cosA-y*sinA;
flX[3]=xc-x*cosA+y*sinA;
flY[0]=yc+y*cosA+x*sinA;
flY[1]=yc-y*cosA+x*sinA;
flY[2]=yc+y*cosA-x*sinA;
flY[3]=yc-y*cosA-x*sinA;
i=0;
}
x++;
dx+=2*bb;
di+=dx+bb;
if(di>=0)
{
dy-=2*aa;
di-=dy;
y--;
}
}
pDC->MoveTo(flX[0],flY[0]);
pDC->LineTo(xc+x*cosA-y*sinA,yc+y*cosA+x*sinA);
pDC->MoveTo(flX[1],flY[1]);
pDC->LineTo(xc+x*cosA+y*sinA,yc-y*cosA+x*sinA);
pDC->MoveTo(flX[2],flY[2]);
pDC->LineTo(xc-x*cosA-y*sinA,yc+y*cosA-x*sinA);
pDC->MoveTo(flX[3],flY[3]);
pDC->LineTo(xc-x*cosA+y*sinA,yc-y*cosA-x*sinA);
di+=int((3*(aa-bb)-2*(dx-dy))/4+0.5);
flX[0]=xc+x*cosA-y*sinA;
flX[1]=xc+x*cosA+y*sinA;
flX[2]=xc-x*cosA-y*sinA;
flX[3]=xc-x*cosA+y*sinA;
flY[0]=yc+y*cosA+x*sinA;
flY[1]=yc-y*cosA+x*sinA;
flY[2]=yc+y*cosA-x*sinA;
flY[3]=yc-y*cosA-x*sinA;
i=0;
while(y>0)
{
i++;
if(i==5)
{
pDC->MoveTo(flX[0],flY[0]);
pDC->LineTo(xc+x*cosA-y*sinA,yc+y*cosA+x*sinA);
pDC->MoveTo(flX[1],flY[1]);
pDC->LineTo(xc+x*cosA+y*sinA,yc-y*cosA+x*sinA);
pDC->MoveTo(flX[2],flY[2]);
pDC->LineTo(xc-x*cosA-y*sinA,yc+y*cosA-x*sinA);
pDC->MoveTo(flX[3],flY[3]);
pDC->LineTo(xc-x*cosA+y*sinA,yc-y*cosA-x*sinA);
flX[0]=xc+x*cosA-y*sinA;
flX[1]=xc+x*cosA+y*sinA;
flX[2]=xc-x*cosA-y*sinA;
flX[3]=xc-x*cosA+y*sinA;
flY[0]=yc+y*cosA+x*sinA;
flY[1]=yc-y*cosA+x*sinA;
flY[2]=yc+y*cosA-x*sinA;
flY[3]=yc-y*cosA-x*sinA;
i=0;
}
y--;
dy-=2*aa;
di+=aa-dy;
if(di<0)
{
dx+=2*bb;
di+=dx;
x++;
}
}
pDC->MoveTo(flX[0],flY[0]);
pDC->LineTo(xc+x*cosA-y*sinA,yc+y*cosA+x*sinA);
pDC->MoveTo(flX[1],flY[1]);
pDC->LineTo(xc+x*cosA+y*sinA,yc-y*cosA+x*sinA);
pDC->MoveTo(flX[2],flY[2]);
pDC->LineTo(xc-x*cosA-y*sinA,yc+y*cosA-x*sinA);
pDC->MoveTo(flX[3],flY[3]);
pDC->LineTo(xc-x*cosA+y*sinA,yc-y*cosA-x*sinA);
}
