How to generate alt attributes with php / filters?

Maybe not the best solution, but did it like this:

function add_alt_tags($content)
{
    global $post;
    $content = str_replace('alt=""', 'alt="'.$post->post_title .'"',
    $content);
    return $content;
}
add_filter('the_content', 'add_alt_tags', 100);