Hi I was also in the same situation as you can use the titles of the entries in the images as alt agregre only a function in functions.php and edit some lines thumb.php
PHP Code:
//alt imagen by darkcrizt
function add_rel_lightbox($content)
{
//Comprueba en la pagina los enlaces directos a las imagenes (sin los atributos)
$string = '/<a href="(.*?).(jpg|jpeg|png|gif|bmp|ico)"><img(.*?)class="(.*?)wp-image-(.*?)" \/><\/a>/i';
preg_match_all( $string, $content, $matches, PREG_SET_ORDER);
//Comprueba si el adjunto tiene refetencia
foreach ($matches as $val)
{
$slimbox_caption = '';
$post = get_post($val[5]);
$slimbox_caption = esc_attr( $post->post_content );
//Sustituye al instancia con el Lightbox y las refetencias. No fallará si leyenda está vacía.
$string = '<a href="' . $val[1] . '.' . $val[2] . '"><img' . $val[3] . 'class="' . $val[4] . 'wp-image-' . $val[5] . '" /></a>';
$replace = '<a href="' . $val[1] . '.' . $val[2] . '" ><img' . $val[3] . 'class="photo thumb ' . $val[4] . 'wp-image-' . $val[5] . '" itemprop="photo" rel="v:photo" alt="'.get_the_title().'"/></a>';
$content = str_replace( $string, $replace, $content);
}
return $content;
}
/* Filter Hook */
add_filter('the_content', 'add_rel_lightbox', 2);
in thumb.php looking for this line
PHP Code:
$bfa_thumb .= '<img src="' . $thumbimage['url'] . '" width="' . $thumbimage['width'] . '" height="' . $thumbimage['height'] . '" />
<span></span>';
and change it to this
PHP Code:
/* alt in images by darkcrrizt - seo */
$bfa_thumb .= '<img rel="v:photo" itemprop="image" class="photo" src="' . $thumbimage['url'] . '" width="' . $thumbimage['width'] . '" height="' . $thumbimage['height'] . '" alt="'.get_the_title().'" />
<span></span>';