featured image in post - shortcode

//2012 oct alchymyth @ transformationpowertools.com
//shortcode to insert post_thumbnail into content
//usage [thumbnail size=medium align=left]

add_shortcode('thumbnail','insert_post_thumbnail_into_content');

function  insert_post_thumbnail_into_content( $atts ) {
   extract( shortcode_atts( array(
      'size' => 'post-thumbnail', // any of the possible post thumbnail sizes - defaults to 'thumbnail'
      'align' => 'none' // any of the alignments 'left', 'right', 'center', 'none' - defaults to 'none'
      ), $atts ) );
    global $post;

    if( ! get_post_thumbnail_id( $post->ID ) ) return false; //no thumbnail found

//alignment check
    if( !in_array( $align, array( 'left', 'right', 'center', 'none' ) ) ) $align = 'none';
    $align = 'align' . $align;

//thumbnail size check
    if( !(preg_match( '|array\((([ 0-9])+,([ 0-9])+)\)|', $size ) === 1) && !in_array( $size, get_intermediate_image_sizes() ) ) $size = 'post-thumbnail';
    if( preg_match( '|array\((([ 0-9])+,([ 0-9])+)\)|', $size, $match ) === 1 ) $sizewh = explode( ',', $match[1] ); $size = array( trim( $sizewh[0] ), trim( $sizewh[1] ) );

//get the post thumbnail
    $thumbnail = get_the_post_thumbnail( $post->ID, $size );

//integrate the alignment class
    $thumbnail = str_replace( 'class="', 'class="' . $align . ' ', $thumbnail ); //add alignment class

return $thumbnail;
}