縮略圖的方法

/*
 * _thumb 獲得文件縮略圖
* @access public 表示函數對外公開
* @param $_filename 圖片路徑
* @param $_percent 縮略比例
* return 一張圖片
* */
function _thumb($_filename,$_percent){
    //生成png表頭文件
    header("Content-type:image/png");
    $_n = explode(".",$_filename);
    //取得圖片的寬和高
    list($_width,$_height)=getimagesize($_filename);
    //生成新的寬和高
    $_new_width = $_width*$_percent;
    $_new_height = $_height*$_percent;
    //創建一個以0.4比例的新畫布
    $_new_image = imagecreatetruecolor($_new_width, $_new_height);
    //用已經有的照片創建畫布
    switch($_n[1]){
     case 'png':$_image = imagecreatefromjpeg($_filename);
     break;
     case 'jpg':$_image = imagecreatefromjpeg($_filename);
     break;
     case 'gif':$_image = imagecreatefromgif($_filename);
     break;
    }
    
    imagecopyresampled($_new_image, $_image, 0, 0, 0, 0, $_new_width, $_new_height, $_width, $_height);
    imagepng($_new_image);
    imagedestroy($_new_image);
    imagedestroy($_image);    
}