php gd库实现远程图片下载功能

<?php
header("Content-type:text/html ; charset=utf-8");
 
if (!empty($_POST['submit'])){
 $url = $_POST['url'];
 $pictureName = $_POST['pictureName'];
 $img = getPicture($url,$pictureName);
 echo '<pre><img class="lazyload" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB/AAffA0nNPuCLAAAAAElFTkSuQmCC" data-original="'.$img.'"></pre>';
 }
function getPicture($url,$pictureName){
 if ($url == "") return false;
 //获取图片的扩展名
 $info = getimagesize($url);
 $mime = $info['mime'];
 $type = substr(strrchr($mime,'/'), 1);
 //不同的图片类型选择不同的图片生成和保存函数
 switch($type){
  case 'jpeg':
   $img_create_func = 'imagecreatefromjpeg';
   $img_save_func = 'imagejpeg';
   $new_img_ext = 'jpg';
   break;
  case 'png':
   $img_create_func = 'imagecreatefrompng';
   $img_save_func = 'imagepng';
   $new_img_ext = 'png';
   break;
  case 'bmp':
   $img_create_func = 'imagecreatefrombmp';
   $img_save_func = 'imagebmp';
   $new_img_ext = 'bmp';
   break;
  case 'gif':
   $img_create_func = 'imagecreatefromgif';
   $img_save_func = 'imagegif';
   $new_img_ext = 'gif';
   break;
  case 'vnd.wap.wbmp':
   $img_create_func = 'imagecreatefromwbmp';
   $img_save_func = 'imagewbmp';
   $new_img_ext = 'bmp';
   break;
  case 'xbm':
   $img_create_func = 'imagecreatefromxbm';
   $img_save_func = 'imagexbm';
   $new_img_ext = 'xbm';
   break;
  default:
   $img_create_func = 'imagecreatefromjpeg';
   $img_save_func = 'imagejpeg';
   $new_img_ext = 'jpg';     
 }
 if ($pictureName == ""){
  $pictureName = time().".{$new_img_ext}";
 }else{
  $pictureName = $pictureName.".{$new_img_ext}";
 }
 $src_im = $img_create_func($url); //由url创建新图片
 $img_save_func($src_im, $pictureName); //输出文件到文件
 return $pictureName;
}
 
?>
<form method="POST" action="">
远程url地址：<input type="text" name="url" size=20 /><br />
文件名称：<input type="text" name="pictureName" size=20 />
<input type="submit" name="submit" value="下载" />
</form>