Header Image using WP_Customize_Image_Control

gistfile1.phtml

<?php

        if ( current_theme_supports( 'onehundred-header-image' ) ) {

                function myplugin_header_image_customize_register( $wp_customize ) {
                        // Pre-selected header images.
                        $wp_customize->add_setting( 'header_image_selection', array(
                                'default'               => 'default',
                                'sanitize_callback'     => 'myplugin_sanitize_header_image_select_choice',
                                'transport'             => 'postMessage',
                        ) );
                        $wp_customize->add_control( 'header_image_selection', array(
                                'label'                 => __( 'Header Image' ),
                                'description'           => __( 'Choose an image from the options below.' ), 
                                'section'               => 'stock_images',
                                'type'                  => 'select',
                                'choices'               => myplugin_get_header_image_select_choices(), // found in themes 'skins' folder
                                'priority'              => 5,
                        ) );
                        // Custom header image.
                        $wp_customize->add_setting( 'header_image_custom', array(
                                'sanitize_callback'     => 'myplugin_sanitize_header_image_custom',
                        ) );
                        $wp_customize->add_control( new WP_Customize_Image_Control( $wp_customize, 'header_image_custom', array(
                                'label'                 => __( 'Header Image' ),
                                'section'               => 'custom_images',
                                'priority'              => 10,
                        ) ) );
                }
                add_action( 'customize_register', 'myplugin_header_image_customize_register' );
                
                function myplugin_sanitize_header_image_select_choice( $value ) {
                        $choices = myplugin_get_header_image_select_choices();

                        $allowed_choices = array_keys( $choices );
                        if ( ! in_array( $value, $allowed_choices ) ) {
                                $value = 'default';
                        }

                        return $value;
                }

                function myplugin_sanitize_header_image_custom( $value ) {
                        $image_url = '';

                        $image_id = '';

                        $filetype = wp_check_filetype( $value );
                
                        if ( $filetype["ext"] ) {
                                $image_url = esc_url_raw( $value );

                                // Convert Attachment (Image) URL to a Post ID.
                                $image_id = attachment_url_to_postid( $image_url );

                                // Save the Post ID.
                                set_theme_mod( 'header_image_custom_id', $image_id );
                        }

                        // If Image is deleted, remove Post ID reference. 
                        if ( ! $image_url ) {
                                set_theme_mod( 'header_image_custom_id', '' );                                
                        }               
                
                        return $image_url;
                }

                function myplugin_site_header_background_image_css() {
                        $template = get_template_directory_uri();
                        $industry = get_option( 'myplugin_industry', 'construction' );
                        $filename = get_theme_mod( 'header_image_selection', 'default' );
                
                        $header_image_custom = get_theme_mod( 'header_image_custom' );
                        $header_image_custom_id = get_theme_mod( 'header_image_custom_id' );
                
                        global $wp_customize;
                
                        echo '<style type="text/css" id="custom-theme-css">';
                                        if ( $header_image_custom && isset( $wp_customize ) ) {
                                                // We need to do a check here as Customizer view will not work properly if we're manipulating using an ID.
                                                echo '.site-header { background-image: url("' . esc_url( $header_image_custom ) . '") } ';
                                        }
                                        elseif ( $header_image_custom_id ) {
                                                $id = absint( $header_image_custom_id );
                                                $image_array = wp_get_attachment_image_src( $id, 'large' );
                                                $image = $image_array[0];
                                                echo '.site-header { background-image: url("' . esc_url( $image ) . '"); } ';
                                        }
                                        else {
                                                echo '.site-header { background-image: url("' . esc_url( $template ) . '/skins/' . esc_attr( $industry ) . '/header-' . esc_attr( $filename ) . '.jpg") } '; 
                                        }
                        echo '</style>';
                }

        }