Post Thumbnail / image

Hi all. I used Wordpress 3+ version. On the home page, i don't want to have the picture or thumbnail, but only when I go there inside the article. I found some useful code, but it is for Thumbnail and don't for image, or i think it wrong?

First in index.php
<?php the_post_thumbnail(); ?>

The second in functions.php

<?php

if (function_exists('add_theme_support')) {
add_theme_support('post-thumbnails');
set_post_thumbnail_size('medium'));
}
?>

<?php
// If WordPress 2.9 or above and a Post Thumbnail has been specified
if ((function_exists('has_post_thumbnail')) && (has_post_thumbnail())) {
the_post_thumbnail('medium', array('class' => 'post-thumbnail', 'alt' => ''.get_the_title().''));
}
// Or if a custom field post image has been specified
else if (get_post_meta($post->ID, 'post_image_value', true)) {
$postimage = get_post_meta($post->ID, 'post_image_value', true);
echo '<img src="'.$postimage.'" alt="'.get_the_title().'" class="post-thumbnail" />';
}
?>

if i add this code to function.php, i will solve my problem?


add_filter( 'post_thumbnail_size', 'my_post_image_size' );
function my_post_image_size( $size )
{ $size = 'medium'; return $size; }

Thanks in advanced