Image count using computed field

I've read that it's possible to add another field to the table which counts the images in each album.
Anyone who has managed to do that and could share their work? I'm really lost on if I have to add the computed field to the galleri-node or image-node and how to calculate the relation between them..

This is my current view:

$view = new view;
$view->name = 'galleries_listing';
$view->description = 'A page view displaying teasers of all existing galleries.';
$view->tag = '';
$view->view_php = '';
$view->base_table = 'node';
$view->is_cacheable = FALSE;
$view->api_version = 2;
$view->disabled = FALSE; /* Edit this to true to make a default view disabled initially */
$handler = $view->new_display('default', 'Gallery page (list of galleries)', 'default');
$handler->override_option('relationships', array(
  'field_gallery_nid' => array(
    'label' => 'Gallery',
    'required' => 0,
    'delta' => -1,
    'id' => 'field_gallery_nid',
    'table' => 'node_data_field_gallery',
    'field' => 'field_gallery_nid',
    'relationship' => 'none',
  ),
));
$handler->override_option('fields', array(
  'name' => array(
    'label' => '',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'strip_tags' => 0,
      'html' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'link_to_taxonomy' => 0,
    'exclude' => 1,
    'id' => 'name',
    'table' => 'term_data',
    'field' => 'name',
    'override' => array(
      'button' => 'Override',
    ),
    'relationship' => 'field_gallery_nid',
  ),
  'field_gallery_image_fid' => array(
    'label' => 'Siste bilde',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'strip_tags' => 0,
      'html' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'link_to_node' => 0,
    'label_type' => 'custom',
    'format' => 'imagefield__lightbox2__gallery_last_image__original',
    'multiple' => array(
      'group' => TRUE,
      'multiple_number' => '',
      'multiple_from' => '',
      'multiple_reversed' => FALSE,
    ),
    'exclude' => 0,
    'id' => 'field_gallery_image_fid',
    'table' => 'node_data_field_gallery_image',
    'field' => 'field_gallery_image_fid',
    'relationship' => 'none',
    'override' => array(
      'button' => 'Override',
    ),
  ),
  'title' => array(
    'label' => '',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'strip_tags' => 0,
      'html' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'link_to_node' => 1,
    'exclude' => 1,
    'id' => 'title',
    'table' => 'node',
    'field' => 'title',
    'override' => array(
      'button' => 'Override',
    ),
    'relationship' => 'field_gallery_nid',
  ),
  'body' => array(
    'label' => 'Album',
    'alter' => array(
      'alter_text' => 1,
      'text' => '[title]<br />[body]',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'strip_tags' => 0,
      'html' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'exclude' => 0,
    'id' => 'body',
    'table' => 'node_revisions',
    'field' => 'body',
    'relationship' => 'field_gallery_nid',
  ),
  'subject' => array(
    'label' => '',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'strip_tags' => 0,
      'html' => 0,
    ),
    'empty' => 'Ingen kommentarer enda',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'link_to_comment' => 1,
    'exclude' => 1,
    'id' => 'subject',
    'table' => 'comments',
    'field' => 'subject',
    'relationship' => 'none',
    'override' => array(
      'button' => 'Override',
    ),
  ),
  'last_comment_timestamp' => array(
    'label' => 'Siste kommentar',
    'alter' => array(
      'alter_text' => 1,
      'text' => '[subject]<br />
[last_comment_timestamp]',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'target' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'strip_tags' => 0,
      'html' => 0,
    ),
    'empty' => '',
    'hide_empty' => 0,
    'empty_zero' => 0,
    'date_format' => 'time ago',
    'custom_date_format' => '',
    'exclude' => 0,
    'id' => 'last_comment_timestamp',
    'table' => 'node_comment_statistics',
    'field' => 'last_comment_timestamp',
    'relationship' => 'none',
    'override' => array(
      'button' => 'Override',
    ),
  ),
));
$handler->override_option('sorts', array(
  'title' => array(
    'order' => 'ASC',
    'id' => 'title',
    'table' => 'node',
    'field' => 'title',
    'override' => array(
      'button' => 'Override',
    ),
    'relationship' => 'none',
  ),
));
$handler->override_option('filters', array(
  'status_extra' => array(
    'operator' => '=',
    'value' => '',
    'group' => '0',
    'exposed' => FALSE,
    'expose' => array(
      'operator' => FALSE,
      'label' => '',
    ),
    'id' => 'status_extra',
    'table' => 'node',
    'field' => 'status_extra',
    'relationship' => 'none',
  ),
  'type' => array(
    'operator' => 'in',
    'value' => array(
      'gallery_image' => 'gallery_image',
    ),
    'group' => '0',
    'exposed' => FALSE,
    'expose' => array(
      'operator' => FALSE,
      'label' => '',
    ),
    'id' => 'type',
    'table' => 'node',
    'field' => 'type',
    'relationship' => 'none',
  ),
));
$handler->override_option('access', array(
  'type' => 'none',
));
$handler->override_option('cache', array(
  'type' => 'none',
));
$handler->override_option('distinct', 1);
$handler->override_option('style_plugin', 'table');
$handler->override_option('style_options', array(
  'grouping' => 'name',
  'override' => 1,
  'sticky' => 0,
  'order' => 'asc',
  'columns' => array(
    'title' => 'title',
    'name' => 'name',
  ),
  'info' => array(
    'title' => array(
      'sortable' => 0,
      'separator' => '',
    ),
    'name' => array(
      'sortable' => 0,
      'separator' => '',
    ),
  ),
  'default' => '-1',
));
$handler->override_option('row_plugin', 'node');
$handler->override_option('row_options', array(
  'relationship' => 'none',
  'build_mode' => 'teaser',
  'links' => 1,
  'comments' => 0,
));