function add_image_alt_title_tags($content) {
    global $post;
    $post_title = $post->post_title;
    $pattern = '/<img(.*?)\/>/i';
    preg_match_all($pattern, $content, $matches);
    foreach ($matches[0] as $index => $img_tag) {
        if (strpos($img_tag, ' alt=') === false || preg_match('/ alt=["\']\s*["\']/', $img_tag)) {
            $replacement = preg_replace('/<img/', '<img alt="' . $post_title . ' ' . ($index + 1) . '" title="' . $post_title . ' ' . ($index + 1) . '"', $img_tag);
            $content = str_replace($img_tag, $replacement, $content);
        }
    }
    return $content;
}
add_filter('the_content', 'add_image_alt_title_tags');