Aqua Resizer功能错误

I don't know if I accidentally messed with something, but for some reason when I visit my screenshot pages, I get this error:

Fatal error: Call to undefined function aq_resize() in /single-screenshots.php on line 36

The code on that page is this:

<?php
                    // BEGIN SCREENSHOTS GALLERY
                    $attachment_args = array(
                         'post_type' => 'attachment',
                         'numberposts' => -1,          // one attachement image per post
                         'post_status' => null,
                         'post_parent' =>$post->ID,
                         'orderby' => 'menu_order ID'
                    );
                    $attachments = get_posts($attachment_args);
                    if ($attachments) {
                      foreach($attachments as $gall_image )                                                                 
                      {
                        $att_img =  wp_get_attachment_url( $gall_image->ID);
                        echo '<li>';
                        echo '<a class="grouped_elements" rel="group1" href="'.$att_img.'" title="'.$gall_image->post_title.'">';
                        echo  '<img src="'. aq_resize($att_img, 140, 100, true) .'" alt=""/>';
                        echo '</a>';
                        echo '</li>';
                      }
                    }

                    ?>

I'm not proficient in PHP so I have no clue what might have caused this? Any ideas?

Simple answer: It can't find the function aq_resize().

Insure that aq_resizer.php is included in your code.

Read up on how to use Aqua-Resizer.