WordPress/wp-content/themes/twentynineteen/inc/helper-functions.php

<?php
/**
 * Common theme functions
 *
 * @package WordPress
 * @subpackage Twenty_Nineteen
 * @since Twenty Nineteen 1.5
 */

/**
 * Determines if post thumbnail can be displayed.
 */
function twentynineteen_can_show_post_thumbnail() {
	return apply_filters( 'twentynineteen_can_show_post_thumbnail', ! post_password_required() && ! is_attachment() && has_post_thumbnail() );
}

/**
 * Returns true if image filters are enabled on the theme options.
 */
function twentynineteen_image_filters_enabled() {
	return 0 !== get_theme_mod( 'image_filter', 1 );
}

/**
 * Returns the size for avatars used in the theme.
 */
function twentynineteen_get_avatar_size() {
	return 60;
}

/**
 * Returns true if comment is by author of the post.
 *
 * @see get_comment_class()
 */
function twentynineteen_is_comment_by_post_author( $comment = null ) {
	if ( is_object( $comment ) && $comment->user_id > 0 ) {
		$user = get_userdata( $comment->user_id );
		$post = get_post( $comment->comment_post_ID );
		if ( ! empty( $user ) && ! empty( $post ) ) {
			return $comment->user_id === $post->post_author;
		}
	}
	return false;
}

/**
 * Returns information about the current post's discussion, with cache support.
 */
function twentynineteen_get_discussion_data() {
	static $discussion, $post_id;

	$current_post_id = get_the_ID();
	if ( $current_post_id === $post_id ) {
		return $discussion; /* If we have discussion information for post ID, return cached object */
	} else {
		$post_id = $current_post_id;
	}

	$comments = get_comments(
		array(
			'post_id' => $current_post_id,
			'orderby' => 'comment_date_gmt',
			'order'   => get_option( 'comment_order', 'asc' ), /* Respect comment order from Settings » Discussion. */
			'status'  => 'approve',
			'number'  => 20, /* Only retrieve the last 20 comments, as the end goal is just 6 unique authors */
		)
	);

	$authors = array();
	foreach ( $comments as $comment ) {
		$authors[] = ( (int) $comment->user_id > 0 ) ? (int) $comment->user_id : $comment->comment_author_email;
	}

	$authors    = array_unique( $authors );
	$discussion = (object) array(
		'authors'   => array_slice( $authors, 0, 6 ),           /* Six unique authors commenting on the post. */
		'responses' => get_comments_number( $current_post_id ), /* Number of responses. */
	);

	return $discussion;
}

/**
 * Converts HSL to HEX colors.
 */
function twentynineteen_hsl_hex( $h, $s, $l, $to_hex = true ) {

	$h /= 360;
	$s /= 100;
	$l /= 100;

	$r = $l;
	$g = $l;
	$b = $l;
	$v = ( $l <= 0.5 ) ? ( $l * ( 1.0 + $s ) ) : ( $l + $s - $l * $s );

	if ( $v > 0 ) {
		$m       = $l + $l - $v;
		$sv      = ( $v - $m ) / $v;
		$h      *= 6.0;
		$sextant = floor( $h );
		$fract   = $h - $sextant;
		$vsf     = $v * $sv * $fract;
		$mid1    = $m + $vsf;
		$mid2    = $v - $vsf;

		switch ( $sextant ) {
			case 0:
				$r = $v;
				$g = $mid1;
				$b = $m;
				break;
			case 1:
				$r = $mid2;
				$g = $v;
				$b = $m;
				break;
			case 2:
				$r = $m;
				$g = $v;
				$b = $mid1;
				break;
			case 3:
				$r = $m;
				$g = $mid2;
				$b = $v;
				break;
			case 4:
				$r = $mid1;
				$g = $m;
				$b = $v;
				break;
			case 5:
				$r = $v;
				$g = $m;
				$b = $mid2;
				break;
		}
	}

	$r = round( $r * 255, 0 );
	$g = round( $g * 255, 0 );
	$b = round( $b * 255, 0 );

	if ( $to_hex ) {

		$r = ( $r < 15 ) ? '0' . dechex( $r ) : dechex( $r );
		$g = ( $g < 15 ) ? '0' . dechex( $g ) : dechex( $g );
		$b = ( $b < 15 ) ? '0' . dechex( $b ) : dechex( $b );

		return "#$r$g$b";

	}

	return "rgb($r, $g, $b)";
}