php简单实用生成缩略图代码

$w?$resizewidth=$w:$resizewidth=400;// 生成图片的宽度
$h?$resizeheight=$h:$resizeheight=400;// 生成图片的高度
function resizeimage($im,$maxwidth,$maxheight,$name){
    $width = imagesx($im);
    $height = imagesy($im);
    if(($maxwidth && $width > $maxwidth) || ($maxheight && $height > $maxheight)){
        if($maxwidth && $width > $maxwidth){
            $widthratio = $maxwidth/$width;
            $resizewidth=true;
        }
        if($maxheight && $height > $maxheight){
            $heightratio = $maxheight/$height;
            $resizeheight=true;
        }
        if($resizewidth && $resizeheight){
            if($widthratio                 $ratio = $widthratio;
            }else{
                $ratio = $heightratio;
            }
        }elseif($resizewidth){
            $ratio = $widthratio;
        }elseif($resizeheight){
            $ratio = $heightratio;
        }
        $newwidth = $width * $ratio;
        $newheight = $height * $ratio;
        if(function_exists("imagecopyresampled")){
              $newim = imagecreatetruecolor($newwidth, $newheight);
              imagecopyresampled($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
        }else{
            $newim = imagecreate($newwidth, $newheight);
              imagecopyresized($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
        }
        imagejpeg ($newim,$name);
        imagedestroy ($newim);
    }else{
        imagejpeg ($im,$name);
    }
}

if($_files['uploadfile']['size']){
    if($_files['uploadfile']['type'] == "image/pjpeg"){
        $im = imagecreatefromjpeg($_files['uploadfile']['tmp_name']);
    }elseif($_files['uploadfile']['type'] == "image/x-png"){
        $im = imagecreatefrompng($_files['uploadfile']['tmp_name']);
    }elseif($_files['uploadfile']['type'] == "image/gif"){
        $im = imagecreatefromgif($_files['uploadfile']['tmp_name']);
    }
    if($im){
        if(file_exists('bbs.jpg')){
            unlink('bbs.jpg');
        }
        resizeimage($im,$resizewidth,$resizeheight,'bbs.jpg');
        imagedestroy ($im);
  
    }
}
//$uploadfile="www.111cn.net.jpg";
?>