Untitled

Add image as attachment link in Post topic
$image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'your-image-size' )

echo $image[0] ;is your link

<?php if (has_post_thumbnail( $post->ID ) ): ?>
<?php $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'full' ); ?>
<a href='<?php echo $image[0]; ?>'> my image link </a>

// Get URL of first image in a post

function postimage( $echo = true ) {
    $image = get_children( array(
        'post_parent' => get_the_ID(),
        'post_type' => 'attachment',
        'numberposts' => 1,
        'order' => 'asc',
        'orderby' => 'ID',
        'post_mime_type' => 'image',
    ) );
    $image_url = ( $image ) ? wp_get_attachment_url( current($image)->ID ) : "No Image";
    if( $echo )
        echo $image_url;
    else
        return $image_url;
}