海报微信头像变圆方法

前阵子有需求做生成海报，海报需要有用户头像昵称，头像是方的，但是老板要求头像改成圆的，倒腾了好一阵让我找到这个方法，记录一下

 public  function test($url,$path='upload/images/'){  
       
        $w = 132;  $h=132; // original size  微信默认头像大小 高132,宽132
        $original_path= $url; //头像地址 
        $dest_path = $path.uniqid().'.png'; 
          //创建目录
            if(!file_exists($path))
            {
               
                mkdir($path,0777,true);
            }
        $src = imagecreatefromstring(file_get_contents($original_path));  
        $newpic = imagecreatetruecolor($w,$h);  
        imagealphablending($newpic,false);  
        $transparent = imagecolorallocatealpha($newpic, 0, 0, 0, 127);  
        $r=$w/2;  
        for($x=0;$x<$w;$x++)  
            for($y=0;$y<$h;$y++){  
                $c = imagecolorat($src,$x,$y);  
                $_x = $x - $w/2;  
                $_y = $y - $h/2;  
                if((($_x*$_x) + ($_y*$_y)) < ($r*$r)){  
                    imagesetpixel($newpic,$x,$y,$c);  
                }else{  
                    imagesetpixel($newpic,$x,$y,$transparent);  
                }  
            }  
        imagesavealpha($newpic, true);  
        imagepng($newpic, $dest_path);  
        imagedestroy($newpic);  
        imagedestroy($src);  
        return $dest_path;  
    }