Filter by User Name

Hello:

I have a link that varies by user.
For now, it is work filtering by user id, but I need the code filter by username.

My actual code is:

<?php $user_id = get_current_user_id();
if ($user_id == 6) {
echo '<a title="Download" href="http://www.mypage.cl/any_url-A/" rel="nofollow">';
} else {
echo '<a title="Download" href="http://www.mypage.cl/any_url-B/" rel="nofollow">';}?>
<img src="http://www.mypage.cl/my_image-gif/" width="250" height="48" />
</a>
<?php global $post; $myposts = get_posts('numberposts=1&category_name=download'); foreach($myposts as $post) : setup_postdata($post);
 the_content();
 if(has_post_thumbnail()) {the_post_thumbnail();}
 endforeach; ?>

Thank you!