/*任意多边形关于任意直线的对称变换*/
#include <graphics.h>
#include <math.h>
void main()
{
float co,si;
int x,y,pt[100]={100,50},tx;
float a,b,c;
int i,a1,n,af;float dtheta,theta,aff;
float q2,q1;
int gdriver=DETECT,gmode;
initgraph(&gdriver,&gmode,"c:\\win-tc");
cleardevice();
setbkcolor(9);
setcolor(4);
line(10,250,450,250); /*坐标轴*/
line(250,10,250,450);
printf("input the a1 ,n and af(exp:100,4,0):\n");/*a1为边长，n为几边形，af为与x轴正向的夹角*/
scanf("%d,%d,%d",&a1,&n,&af);
while(n<3)
{printf("ERROR!");
printf("input the a1 ,n and af(exp:100,4,0):\n");
scanf("%d,%d,%d",&a1,&n,&af);
}
dtheta=6.28318/n;
theta=af*0.0174533;
moveto(pt[0]+250,-pt[1]+250);
for(i=2;i<2*n;i=i+2)
{ pt[i]=pt[i-2]+a1*cos(theta);
pt[i+1]=pt[i-1]+a1*sin(theta);
lineto(pt[i]+250,-pt[i+1]+250);
theta=theta+dtheta;
}
lineto(pt[0]+250,-pt[1]+250);
printf("please input a,b,c,which is in ax+by+c=0:exp:1,-1,100):\n");
scanf("%f,%f,%f",&a,&b,&c);
if(a==0)
{
line(30,(250+c/b),450,(250+c/b));
getch();
for(i=0;i<=2*n;i=i+2)
{
pt[i+1]=-(pt[i+1]+c/b)-c/b;
}
moveto(pt[0]+250,-pt[1]+250);
for(i=2;i<2*n;i=i+2)
lineto(pt[i]+250,-pt[i+1]+250);
lineto(pt[0]+250,-pt[1]+250);
getch();
}
else if(b==0)
{line((250-c/a),100,(250-c/a),450);
getch();
for(i=0;i<2*n;i=i+2)
pt[i]=-(pt[i]+c/a)-c/a;
moveto(pt[0]+250,-pt[1]+250);
for(i=2;i<2*n;i=i+2)
lineto(pt[i]+250,-pt[i+1]+250);
lineto(pt[0]+250,-pt[1]+250);
getch();
}
else
{
line(250-c/a,250,250,250+c/b);
getch();
aff=atan(-a/b) ;
for(i=0;i<2*n;i=i+2)
{ tx= pt[i];
pt[i]=pt[i]*cos(2*aff)+pt[i+1]*sin(2*aff)+(c/a)*(cos(2*aff)-1);
pt[i+1]=tx*sin(2*aff)-pt[i+1]*cos(2*aff)+(c/a)*sin(2*aff);
}
moveto(pt[0]+250,-pt[1]+250);
for(i=2;i<2*n;i=i+2)
lineto(pt[i]+250,-pt[i+1]+250);
lineto(pt[0]+250,-pt[1]+250);
getch();
}
closegraph();
}
