中点画线算法

START

N

Y

END

mark=1?

x++;e = e + 2 * dy;

e 0?

y1y0?

temp = x1;x1 = y1;y1 = temp;

k==0?

y++; e = e - 2 * dx;

(y1 - y0) (x1 - x0) ?

x1=x0?

y1 = -y1;y0 = -y0;mark = 1;

temp = x1;x1 = x0;x0 = temp;\t

temp = y1;y1 = y0;y0 = temp;\t

temp = x0;x0 = y0;y0 = temp;k = 1;

x1x0?

dx = x1 - x0;dy = y1 - y0;e = -dx;x = x0;y = y0;

x=x1?

x1 = -x1;x0 = -x0;mark = 2;

mark=0?

mark=2?