branded-login.php

<?php

/**
 * Custom login page design
 */
function custom_login_page_design() {
	$colors    = wp_get_global_styles( array( 'color' ) );
	$variables = wp_get_global_stylesheet( array( 'variables' ) );
	?>
	<style type="text/css">
	<?php echo esc_html( $variables ); ?>

	body.login {
		background-color: <?php echo esc_attr( $colors['background'] ); ?>;
		color: <?php echo esc_attr( $colors['text'] ); ?>;
	}
	</style>
	<?php

	$custom_logo_id = get_theme_mod( 'custom_logo' );
	if ( $custom_logo_id ) {
		$image = wp_get_attachment_image_src( $custom_logo_id, 'medium' );
		?>
	<style type="text/css">
	#login h1 a, .login h1 a {
		background-image: url(<?php echo esc_attr( $image[0] ); ?>);
		height:<?php echo esc_attr( $image[2] ); ?>px;
		width:<?php echo esc_attr( $image[1] ); ?>px;
		max-width: 100%;
		background-size: contain;
		background-repeat: no-repeat;
		padding-bottom: 30px;
	}
	</style>
		<?php
	}
}
add_action( 'login_enqueue_scripts', 'custom_login_page_design' );