php gd库实现远程图片的下载

<?php
/**
* 远程图片的下载
* by www.jb200.com
*/
header("Content-type:text/html ; charset=utf-8");
 
if (!empty($_POST['submit'])){
  $url = $_POST['url'];
  $pictureName = $_POST['pictureName'];
  $img = getPicture($url,$pictureName);
  echo '<pre><img src="'.$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>