呼啦一阵风
graphics.beginFill(0xFF0000);
halfCircle(graphics, 200,200, 100); // original circle function by senocular (www.senocular.com) from here http://www.actionscript.org/forums/showthread.php3?s=&threadid=30328
function halfCircle(g:Graphics, x:Number,y:Number,r:Number):void {
var c1:Number=r * (Math.SQRT2 - 1);
var c2:Number=r * Math.SQRT2 / 2;
g.moveTo(x+r,y);
g.curveTo(x+r,y+c1,x+c2,y+c2);
g.curveTo(x+c1,y+r,x,y+r);
g.curveTo(x-c1,y+r,x-c2,y+c2);
g.curveTo(x-r,y+c1,x-r,y); // comment in for full circle
/*g.curveTo(x-r,y-c1,x-c2,y-c2);
g.curveTo(x-c1,y-r,x,y-r);
g.curveTo(x+c1,y-r,x+c2,y-c2);
g.curveTo(x+r,y-c1,x+r,y);*/
};