php 图片上传并生成缩略图代码

 if($_FILES['image']['size']){
     if($_FILES['image']['type'] == "image/pjpeg"){
      $im = @imagecreatefromjpeg($_FILES['image']['tmp_name']);
      $n_bmp.='.jpg';
     }elseif($_FILES['image']['type'] == "image/x-png"){
      $im = @imagecreatefrompng($_FILES['image']['tmp_name']);
      $n_bmp.='.png';
     }elseif($_FILES['image']['type'] == "image/gif"){
      $im = @imagecreatefromgif($_FILES['image']['tmp_name']);
      $n_bmp.='.gif';
     }  
    ResizeImage($im,8888,8888,$n_bmp);    
       ImageDestroy ($im);
    $n_tag =1;
      
   }
    
function Uploadfile($str){
   
   $save_path = './product/';//文件保存目录路径
   
   $ext_arr   = array('rar','zip','jpg','gif','png','bmp');//定义允许上传的文件扩展名
   
   $max_size  = 1000000;//最大文件大小
   
   $file_rand ='';
   
   $file_ext  ='';
   
   @mkdir($save_path, 0777); //更改目录权限    
   
   if ($_FILES[$str]['name']) {//有上传文件时
    
    $file_name = $_FILES[$str]['name'];//原文件名
    
    $tmp_name = $_FILES[$str]['tmp_name'];//服务器上临时文件名
    
    $file_size = $_FILES[$str]['size'];//文件大小
    
    if (@is_dir($save_path) === false) {//检查目录
     alert("上传目录不存在。",'');
    }
    
    if (@is_writable($save_path) === false) {//检查目录写权限
     alert("上传目录没有写权限。",'');
    }
    
    if (@is_uploaded_file($tmp_name) === false) {//检查是否已上传
     alert("临时文件可能不是上传文件。",'');
    }
    
    if ($file_size > $max_size) {//检查文件大小
     alert("上传文件大小超过限制。",'');
    }
    
    $temp_arr = explode(".", $file_name);//获得文件扩展名
    $file_ext = array_pop($temp_arr);
    $file_ext = trim($file_ext);
    $file_ext = strtolower($file_ext);
    $file_rand= md5(date("Y-m-d"));
    if (in_array($file_ext, $ext_arr) === false) {//检查扩展名
     alert("上传文件扩展名是不允许的扩展名。",'');
    }
    
    if (move_uploaded_file($tmp_name, $save_path.$file_rand.'.'.$file_ext) === false) {//移动文件
     alert("上传文件失败。",'');
    }    
   } 
  return $save_path.$file_rand.'.'.$file_ext;
 }
 
 
 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 < $heightratio){
   $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,'./product_e/'.$name);
  ImageDestroy ($newim);
  }else{
  ImageJpeg ($im,'./product_e/'.$name);
  }
  }