i think you're attacking the wrong filter... if you look at the function thematic_content() in header-extensions.php you'll see
echo apply_filters('thematic_post', $post);
so the filter to target is actually called thematic_post. idk why they did it that way. i banged my head into the wall over it for a long time. but the important thing to take away from it is that the filter name does not always match the function name. the filter name is the first parameter in the apply_filters statement.
oh and you will need to RETURN something. otherwise you don't actually pass info to the filter.
then you should be able to do something like
function kia_lightbox_thumbs($post){
if ( strtolower($thematic_content_length) == 'excerpt') {
$post = '';
if ( apply_filters( 'thematic_post_thumbs', TRUE) ) {
$post_title = get_the_title();
$size = apply_filters( 'thematic_post_thumb_size' , array(100,100) );
$attr = apply_filters( 'thematic_post_thumb_attr', array('title' => 'Permalink to ' . $post_title) );
if ( has_post_thumbnail() ) {
$image = wp_get_attachment_image_src( get_post_thumbnail_id(), 'full' );
$post = '<a class="entry-thumb" class="lightbox" href="' . $image[0] . '" title="Permalink to ' . get_the_title() . '" >' . get_the_post_thumbnail(get_the_ID(), $size, $attr) . '</a>' . $post;
}
}
}
return $post;
}
$post = '' . get_the_post_thumbnail(get_the_ID(), $size, $attr) . '';
}
add_filter('thematic_content', 'kia_lightbox_thumbs');
you almost surely have to add some kind of class="lightbox" (depending on what plugin you're using) to the link. and the link src needs to point to the full size image, which is what i am doing with wp_get_attachment_image_src() function.
untested, so there could be typos. note, you didn't put the excerpt in yours so i left it out. this will only show the thumbnail with no fallback if there isn't a thumbnail.
