雪花分形

<?
//定义函数,Koch绘图算法
function Draw($x1,$y1,$x2,$y2,$color,$img,$nMax)
{
if(($x1-$x2)*($x1-$x2)+($y1-$y2)*($y1-$y2)&lt;$nMax){
imageline($img,$x1,$y1,$x2,$y2,$color);
}
else{
$x3=$x1+($x2-$x1)/3;
$y3=$y1+($y2-$y1)/3;
$x5=$x2-($x2-$x1)/3;
$y5=$y2-($y2-$y1)/3;
$D=sqrt(($x5-$x3)*($x5-$x3)+($y5-$y3)*($y5-$y3));
$alpha=0.0;
if($x5-$x3==0)$alpha=3.1415926/2;
else {
$x=(float)($y5-$y3)/(float)($x5-$x3);
$alpha=atan($x);
}
if($x5-$x3&lt;0)
$alpha=$alpha+3.1415926;
$x4=$x3+cos($alpha+3.1415926/3)*$D;
$y4=$y3+sin($alpha+3.1415926/3)*$D;
Draw($x1,$y1,$x3,$y3,$color,$img,$nMax);
Draw($x5,$y5,$x2,$y2,$color,$img,$nMax);
Draw($x3,$y3,$x4,$y4,$color,$img,$nMax);
Draw($x4,$y4,$x5,$y5,$color,$img,$nMax);
}
}
//GD绘图
$im = ImageCreate(300, 300);
$color = ImageColorAllocate($im, 0,0,0);
$color_draw = imagecolorallocate($im, 255, 198, 128);
//
Draw(50,200,250,200,$color_draw,$im,$nMax);
Draw(150,27,50,200,$color_draw,$im,$nMax);
Draw(250,200,150,27,$color_draw,$im,$nMax);
//
Header("Content-type: image/png");
ImagePNG($im); //输出图像
ImageDestroy($im); //销毁内存里的图像，释放内存空间
?>