thuật toán Midpoint

// Ve 8 diem doi xung
void Put8Pixel(int x, int y)
{
	putpixel(x, y, Color);
	putpixel(y, x, Color);
	putpixel(y, -x, Color);
	putpixel(x, -y, Color);
	putpixel(-x, -y, Color);
	putpixel(-y, -x, Color);
	putpixel(-y, x, Color);
	putpixel(-x, y, Color);
} // Put8Pixel
void CircleMidPoint (int R)
{
	int x, y;
	x = 0;
	y = R;
	Put8Pixel(x, y);
	p = 1 - R; // 5/4-R
	while (x < y)
	{
		if (p < 0)
			p += 2*x + 3;
		else
		{
			p += 2*(x -y) + 5;
			y--;
		}
		x++;
		Put8Pixel(x, y);
	}
} // CircleMidPoint

#include "iostream"
#include "conio.h"
#include "graphics.h"
#include "math.h"
int color = RED,x,y,R;
void DDX(int x,int y)
{
 putpixel(x,y,color);
 putpixel(y,x,color);
 putpixel(y,-x,color);
 putpixel(x,-y,color);
 putpixel(-x,-y,color);
 putpixel(-y,-x,color);
 putpixel(-y,x,color);
 putpixel(-x,y,color);
}
void MidPoint(int x0,int y0, int R)
{  int x,y, p;
   x=0;
   y=R;
   DDX(x,y);
   p=5/4-R;
   while (x
   {
     if (p<0) p=p+2*x+3 ;
     else
     {
	   p= p+2*(x-y)+5;
	   y=y-1;
     }
     x=x+1;
     DDX(x+x0,y+y0);
     DDX(x+x0,-y+y0);
     DDX(-x+x0,y+y0);
     DDX(-x+x0,-y+y0);
   }
}
void KhoiTao()
{   //int n,m;
   int n = DETECT;
   int m;
  initgraph(&n,&m,"");
}
void main()
{
  KhoiTao();
  printf("\nNhap tam (x,y)="); scanf("%d%d",&x,&y);
  printf("\nNhap ban kinh R="); scanf("%d",&R);
  MidPoint(x,y,R) ;
  getch();
  closegraph();
}

public void put8pixel(int x0, int y0, int x, double y, Color color)
        {
            SetPixel(x0 + x, (int)(y0 - y), color);

            SetPixel((int)(x0 + y), y0 - x, color);

            SetPixel((int)(x0 + y), y0 + x, color);

            SetPixel(x0 + x, (int)(y0 + y), color);

            SetPixel((int)(x0 - y), y0 + x, color);

            SetPixel(x0 - x, (int)(y0 + y), color);

            SetPixel(x0 - x, (int)(y0 - y), color);

            SetPixel((int)(x0 - y), y0 - x, color);
        }
       
        public void DrawCircle(int x1, int y1, int x2, int y2, Color color)
        {
            double r;
            int Dx = Math.Abs(x2 - x1);
            int Dy = Math.Abs(y2 - y1);
            double R = Math.Sqrt(Dx * Dx + Dy * Dy);
            r = R / Math.Sqrt(2);
            put8pixel(x1, y1, 0, R, color);
            for (int i = 1; i < r; i++)
            {
                double j;
                j = Math.Sqrt(Math.Pow(R, 2) - Math.Pow(i, 2));
                put8pixel(x1, y1, i, Math.Round(j), color);
            }
        }  

void HoanVi4So(int &x1, int &y1, int &x2, int &y2)
{
	int a, b;
	a = x1;
	b = y1;

	x1 = x2;
	y1 = y2;

	x2 = a;
	y2 = b;
}

void CGraphics::DrawLine_MidPoint(int x1, int y1, int x2, int y2)
{
	int Dx, Dy, p, c1, c2;
	int x, y;
	int i, dx, dy;

	if(x1 > x2)
		HoanVi4So(x1, y1, x2, y2);

	Dx = x2 - x1;
	Dy = y2 - y1;

	dx = (Dx >= 0) ? 1 : -1;
	dy = (Dy >= 0) ? 1 : -1;

	Dx = abs(Dx);
	Dy = abs(Dy);

	p = 2*Dy - Dx;
	c1 = 2*Dy;
	c2 = 2*(Dy - Dx);

	x = x1;
	y = y1;

	SetPixel(x,y);

	for(i=0; i
	{
		if(p < 0)
			p += c1;
		else
		{
			p += c2;
			y += dy;
		}
		x += dx;
		SetPixel(x,y);
	}
} 

void CGraphics::Set8Pixel(int xc, int yc, int x, int y)
{
	SetPixel(xc+x,yc+y);
	SetPixel(xc+x,yc-y);
	SetPixel(xc-x,yc+y);
	SetPixel(xc-x,yc-y);
	SetPixel(xc+y,yc+x);
	SetPixel(xc+y,yc-x);
	SetPixel(xc-y,yc+x);
	SetPixel(xc-y,yc-x);	
}

void CGraphics::Set8Pixel(int xc, int yc, int x, int y)
{
	SetPixel(xc+x,yc+y);
	SetPixel(xc+x,yc-y);
	SetPixel(xc-x,yc+y);
	SetPixel(xc-x,yc-y);
	SetPixel(xc+y,yc+x);
	SetPixel(xc+y,yc-x);
	SetPixel(xc-y,yc+x);
	SetPixel(xc-y,yc-x);	
}
void CGraphics::DrawCicle_MidPointFull(int xc, int yc, int r)
{
	int x, y, p;
	x = 0; y = r; 
	Set8Pixel(xc, yc, x, y);
	p = 5/4 - r;
	while(x < y)
	{
		if(p < 0)
			p += 2*x + 3;
		else
		{
			p += 2*(x - y) + 5;
			y--;
		}
		x++;
		Set8Pixel(xc, yc, x+xc, y+yc);
		Set8Pixel(xc, yc, x+xc, -y+yc);
		Set8Pixel(xc, yc, -x+xc, y+yc);
		Set8Pixel(xc, yc, -x+xc, -y+yc);
	}
}

// Thuật toán Line MidPiont dành cho cả 8 trường hợp
void CGraphics::DrawLine_MidPoint8th(int x1, int y1, int x2, int y2)
{	int dx, dy, x, y, c1, c2, p;
	dx = abs(x2 - x1);
	dy = abs(y2 - y1);
	p = (dy<<1) - dx;
	if(abs(dx) >= abs(dy))
	{	if(x1 > x2)
		{	hoanvi(x1, x2);
			hoanvi(y1, y2);
		}
		x = x1;
		y = y1;
		c1 = (dy<<1);//dy*2
		c2 = ((dy - dx)<<1); // (dy-dx)*2
		SetPixel(x, y);
		while(x < x2)
		{	if(p < 0)	p += c1;
			else
			{	p += c2;
				if(y1 > y2)	y--;
				else		y++;
			}
			++x;
			SetPixel(x, y);
		}
	}
	else
	{	if(y1 > y2)
		{	hoanvi(x1, x2);
			hoanvi(y1, y2);
		}
		x = x1; y = y1;
		c1 = (dx<<1); c2 = ((dy - dx)>>1);
		SetPixel(x, y);
		while(y < y2)
		{	if(p < 0)	p += c1;
			else
			{	p += c2;
				if(x1 > x2)	x--;
				else		x++;
			}
			++y;
			SetPixel(x, y);
		}
	}
}