- Thuat toan Bresenham de ve duong ellipse */
#include <graphics.h>
#include <conio.h>
#define ROUND(a) ((long)(a+0.5))
void plot(int xc, int yc, int x, int y, int color)
{
putpixel(xc+x, yc+y, color);
putpixel(xc-x, yc+y, color);
putpixel(xc+x, yc-y, color);
putpixel(xc-x, yc-y, color);
}
void Bresenham_Ellipse(int xc, int yc, int xRadius, int yRadius, int color)
{
long x, y, px, py, rx2, ry2, p;
x = 0;
y = yRadius;
rx2 = xRadius * xRadius;
ry2 = yRadius * yRadius;
px = 0;
py = 2 * rx2 * y;
plot(xc, yc, x,y, color);
p = ROUND(ry2-(rx2*yRadius)+(0.25*rx2));
while (px < py)
{
x++;
px += 2*ry2;
if (p<0)
p += ry2 + px;
else
{
y--;
py -= 2*rx2;
p+= ry2 + px - py;
}
plot(xc, yc, x, y, color);
}
p = ROUND(ry2*(x+0.5)*(x+0.5) + rx2*(y-1)*(y-1) - rx2*ry2);
while (y>0)
{
y--;
py -= rx2*2;
if (p>0)
p+=rx2-py;
else
{
x++;
px += ry2*2;
p += rx2 - py + px;
}
plot(xc, yc, x, y, color);
}
}
void main()
{
int gr_drive = DETECT, gr_mode;
initgraph(&gr_drive, &gr_mode, "");
Bresenham_Ellipse(getmaxx() / 2, getmaxy() / 2, 150, 80, 4);
getch();
closegraph();
}
Tiêu đề: Thuat toan Bresenham de ve duong ellipse 
10/07/10, 09:55 pm