gistfile1.txt

add_filter( 'amp_post_template_metadata', 'xyz_amp_modify_json_metadata', 10, 2 );

function xyz_amp_modify_json_metadata( $metadata, $post ) {
    $metadata['@type'] = 'NewsArticle';

    $metadata['publisher']['logo'] = array(
        '@type' => 'ImageObject',
        'url' => 'http://daipresents.com/wp-content/uploads/2016/05/header.201502.jpg',
        'height' => 60,
        'width' => 298,
    );

    if(empty($metadata['image'])) {
      $metadata['image'] = array(
        '@type' => 'ImageObject',
        'url' => 'http://daipresents.com/wp-content/uploads/2015/02/header.201502.jpg',
        'height' => 295,
        'width' => 1105,
      );
    }

    return $metadata;
}