The following code you can use for get the feature image of post in wordpress.
//Example 1
$feat_image = wp_get_attachment_url( get_post_thumbnail_id($post->ID) );
echo '$feat_image';
//Example 2
$large_image_url = wp_get_attachment_image_src( get_post_thumbnail_id(145), 'large');
echo '<a href="' . $large_image_url[0] . '" title="' . the_title_attribute('echo=0') . '" >';
echo get_the_post_thumbnail($post->ID, 'thumbnail');
echo '</a>';