<?php
add_theme_support( 'post-thumbnails', array( 'post', 'carousel-image' ) );
add_image_size( 'post-image', 600, 200, true );
$image_variable = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'post-image' );
echo $image_variable[0];
//href small img
<?php echo $portfolio_image[0];?>

// img src big img
<?php echo $portfolio_large[0]; ?>


?>