画实心圆算法求解

JULY · 发表于 2014-12-25 10:48:58

//画实心圆
//x0,y0:坐标
//r:半径
//color:颜色
void gui_fill_circle(u16 x0,u16 y0,u16 r,u16 color)
{
u32 i;
u32 imax = ((u32)r*707)/1000+1;
u32 sqmax = (u32)r*(u32)r+(u32)r/2;
u32 x=r;
gui_draw_hline(x0-r,y0,2*r,color);
for (i=1;i<=imax;i++)
{
if ((i*i+x*x)>sqmax)// draw lines from outside
{
if (x>imax)
{
gui_draw_hline (x0-i+1,y0+x,2*(i-1),color);
gui_draw_hline (x0-i+1,y0-x,2*(i-1),color);
}
x--;
}
// draw lines from inside (center)
gui_draw_hline(x0-x,y0+i,2*x,color);
gui_draw_hline(x0-x,y0-i,2*x,color);
}
}
请问这两语句是根据什么写出来的？？
u32 imax = ((u32)r*707)/1000+1;
u32 sqmax = (u32)r*(u32)r+(u32)r/2;