function resim_title_alt_ekle($content) {
    global $post;
    $baslik = get_the_title($post->ID);
    $ara = '/<img(.*?)src="(.*?).(bmp|gif|jpeg|jpg|png)"(.*?)>/i';
      $degistir = '<img$1src="$2.$3" title="'.$baslik.'" alt="'.$baslik.'" $4>';
    $content = preg_replace( $ara, $degistir, $content );
    return $content;
}
add_filter( 'the_content', 'resim_title_alt_ekle' );