实现中文圆形印章的PHP类

<?PHP
/*
 * 中文圆形印章类
 * @author lkk/lianq.net
 * @create on 10:03 2012-5-29
 * @example:
 *  $seal = new circleSeal('你我他坐站走东西南北中',75,6,24,16,40);
 *  $seal->doImg();
 */

class circleSeal {
    private $sealString;    //印章字符
    private $strMaxLeng;    //最大字符长度
    private $sealRadius;    //印章半径
    private $rimWidth;      //边框厚度
    private $innerRadius;   //内圆半径
    private $startRadius;   //五角星半径
    private $startAngle;    //五角星倾斜角度
    private $backGround;    //印章颜色
    private $centerDot;     //圆心坐标
    private $img;           //图形资源句柄
    private $font;          //指定的字体
    private $fontSize;      //指定字体大小
    private $width;         //图片宽度
    private $height;        //图片高度
    private $points;        //五角星各点坐标
    private $charRadius;    //字符串半径
    private $charAngle;     //字符串倾斜角度
    private $spacing;       //字符间隔角度

    //构造方法
    public function __construct($str ='',$rad = 75,$rmwidth = 6,$strad = 24,$stang = 0,$crang = 0,$fsize = 16,$inrad =0){
        $this->sealString   = empty($str) ? '印章测试字符串' : $str;
        $this->strMaxLeng   = 12;
        $this->sealRadius   = $rad;
        $this->rimWidth     = $rmwidth;
        $this->startRadius  = $strad;
        $this->startAngle   = $stang;
        $this->charAngle    = $crang;
        $this->centerDot    = array('x'=>$rad,'y'=>$rad);
        $this->font         = dirname(__FILE__) .'/simkai.ttf';
        $this->fontSize     = $fsize;
        $this->innerRadius  = $inrad;   //默认0,没有
        $this->spacing      = 1;
    }

    //创建图片资源
    private function createImg(){
        $this->width        = 2 * $this->sealRadius;
        $this->height       = 2 * $this->sealRadius;
        $this->img          = imagecreate($this->width,$this->height);
        imagecolorresolvealpha($this->img,255,127);
        $this->backGround   = imagecolorallocate($this->img,0);
    }

    //画印章边框
    private function drawRim(){
        for($i=0;$i<$this->rimWidth;$i++){
            imagearc($this->img,$this->centerDot['x'],$this->centerDot['y'],$this->width - $i,$this->height - $i,360,$this->backGround);
        }
    }

    //画内圆
    private function drawInnerCircle(){
        imagearc($this->img,2*$this->innerRadius,$this->backGround);
    }

    //画字符串
    private function drawString(){
        //编码处理
        $charset = mb_detect_encoding($this->sealString);
        if($charset != 'UTF-8'){
            $this->sealString = mb_convert_encoding($this->sealString,'UTF-8','GBK');
        }

        //相关计量
        $this->charRadius = $this->sealRadius - $this->rimWidth - $this->fontSize;  //字符串半径
        $leng   = mb_strlen($this->sealString,'utf8');  //字符串长度
        if($leng > $this->strMaxLeng) $leng = $this->strMaxLeng;
        $avgAngle   = 360 / ($this->strMaxLeng);    //平均字符倾斜度

        //拆分并写入字符串
        $words  = array();  //字符数组
        for($i=0;$i<$leng;$i++){
            $words[] = mb_substr($this->sealString,$i,1,'utf8');
            $r = 630 + $this->charAngle + $avgAngle*($i - $leng/2) + $this->spacing*($i-1);     //坐标角度
            $R = 720 - $this->charAngle + $avgAngle*($leng-2*$i-1)/2 + $this->spacing*(1-$i);   //字符角度
            $x = $this->centerDot['x'] + $this->charRadius * cos(deg2rad($r));  //字符的x坐标
            $y = $this->centerDot['y'] + $this->charRadius * sin(deg2rad($r));  //字符的y坐标
            imagettftext($this->img,$this->fontSize,$R,$x,$y,$this->backGround,$this->font,$words[$i]);
        }
    }   

    //画五角星
    private function drawStart(){
        $ang_out = 18 + $this->startAngle;
        $ang_in  = 56 + $this->startAngle;
        $rad_out = $this->startRadius;
        $rad_in  = $rad_out * 0.382;
        for($i=0;$i<5;$i++){
            //五个顶点坐标
            $this->points[] = $rad_out * cos(2*M_PI/5*$i - deg2rad($ang_out)) + $this->centerDot['x'];
            $this->points[] = $rad_out * sin(2*M_PI/5*$i - deg2rad($ang_out)) + $this->centerDot['y'];

            //内凹的点坐标
            $this->points[] = $rad_in * cos(2*M_PI/5*($i+1) - deg2rad($ang_in)) + $this->centerDot['x'];
            $this->points[] = $rad_in * sin(2*M_PI/5*($i+1) - deg2rad($ang_in)) + $this->centerDot['y'];
        }
        imagefilledpolygon($this->img,$this->points,10,$this->backGround);
    }

    //输出
    private function outPut(){
        header('Content-type:image/png');
        imagepng($this->img);
        imagedestroy($this->img);
    }

    //对外生成
    public function doImg(){
        $this->createImg();
        $this->drawRim();
        $this->drawInnerCircle();
        $this->drawString();
        $this->drawStart();
        $this->outPut();
    }
}