thumbnails.php

<?php
    function thumbnail($path){
        list($ancho, $alto) = getimagesize($path);
        $nuevo_ancho = $nuevo_alto = 150;

        $ext = '.'.pathinfo($path, PATHINFO_EXTENSION);
        $name = pathinfo($path, PATHINFO_FILENAME);
        $dir = pathinfo($path, PATHINFO_DIRNAME);

        $thumb = imagecreatetruecolor($nuevo_ancho, $nuevo_alto);

        if($ext == '.png' || $ext == '.PNG') $origen = imagecreatefrompng($path);
        if($ext == '.jpg' || $ext == '.JPG' || $ext == '.JPEG' || $ext == '.jpeg') $origen = imagecreatefromjpeg($path);
        if($ext == '.gif' || $ext == '.GIF') $origen = imagecreatefromgif($path);

        imagecopyresized($thumb, $origen, 0, 0, 0, 0, $nuevo_ancho, $nuevo_alto, $ancho, $alto);

        $ruta_final = $dir.'/'.$name.'_thumb'.$ext;
        
        if($ext == '.png' || $ext == '.PNG'){
            imagepng($thumb, $ruta_final);
        }else{
            if($ext == '.jpg' || $ext == '.JPG' || $ext == '.JPEG' || $ext == '.jpeg'){
                imagejpeg($thumb, $ruta_final);
            }else{
                if($ext == '.gif' || $ext == '.GIF'){
                    imagegif($thumb, $ruta_final);
                }
            }
        }
    }
 ?>