// 前略
/**
 * Astra get post thumbnail image.
 */
if ( ! function_exists( 'astra_get_post_thumbnail' ) ) {

        /**
         * Astra get post thumbnail image
         *
         * @since 1.0.15
         * @param string  $before Markup before thumbnail image.
         * @param string  $after  Markup after thumbnail image.
         * @param boolean $echo   Output print or return.
         * @return string|void
         */
        function astra_get_post_thumbnail( $before = '', $after = '', $echo = true ) {

                $output = '';

                $check_is_singular = is_singular();
                $check_is_archive  = ( is_archive() || is_search() || is_home() );

                $featured_image = true;
                $post_type      = strval( get_post_type() );

                if ( $check_is_singular ) {
                        $is_featured_image = astra_get_option_meta( 'ast-featured-img' );
                } else {
                        $is_featured_image = astra_get_option( 'ast-featured-img' );
                }

                $featured_image_size = 'large';
                if ( $check_is_archive ) {
                        $featured_image_size = astra_get_option( 'blog-image-size', 'large' );
                }

                if ( 'disabled' === $is_featured_image ) {
                        $featured_image = false;
                }

                $featured_image = apply_filters( 'astra_featured_image_enabled', $featured_image );

                $blog_post_thumb   = astra_get_option( 'blog-post-structure' );
                $single_post_thumb = astra_get_option( 'ast-dynamic-single-' . $post_type . '-structure', array( 'ast-dynamic-' . $post_type . '-post-title', 'ast-dynamic-' . $post_type . '-post-meta' ) );

                if ( ( ( ! $check_is_singular && in_array( 'image', $blog_post_thumb ) ) || ( $check_is_singular && in_array( 'ast-dynamic-single-' . $post_type . '-image', $single_post_thumb ) ) || is_page() ) && has_post_thumbnail() ) {

                        if ( $featured_image && ( ! ( $check_is_singular ) || ( ! post_password_required() && ! is_attachment() && has_post_thumbnail() ) ) ) {

                                $image_size = $check_is_singular ? astra_get_option( 'ast-dynamic-single-' . $post_type . '-article-featured-image-size', 'large' ) : $featured_image_size;
                                $post_thumb = apply_filters(
                                        'astra_featured_image_markup',
                                        get_the_post_thumbnail(
                                                get_the_ID(),
                                                apply_filters( 'astra_post_thumbnail_default_size', $image_size ),
                                                apply_filters( 'astra_post_thumbnail_itemprop', '' )
                                        )
                                );

                                if ( '' != $post_thumb ) {
                                        $output .= '<div class="post-thumb-img-content post-thumb">';
                                        if ( ! $check_is_singular ) {
                                                $output .= apply_filters(
                                                        'astra_blog_post_featured_image_link_before',
                                                        '<a ' . astra_attr(
                                                                'article-image-url',
                                                                array(
                                                                        'class' => '',
                                                                        'href'  => esc_url( get_permalink() ),
                                                                )
                                                        ) . ' >'
                                                );
                                        }
                                        $output .= $post_thumb;
                                        if ( ! $check_is_singular ) {
                                                $output .= apply_filters( 'astra_blog_post_featured_image_link_after', '</a>' );
                                        }
                                        $output .= '</div>';
                                }
                        }
                }

                if ( ! $check_is_singular ) {
                        $output = apply_filters( 'astra_blog_post_featured_image_after', $output );
                }

                $output = apply_filters( 'astra_get_post_thumbnail', $output, $before, $after );

                if ( $echo ) {
                        echo $before . $output . $after; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
                } else {
                        return $before . $output . $after;
                }
        }
}

// 後略

// 前略
/**
 * Render Featured Image for single post at 'astra_entry_before' hook before post <article>
 *
 * @since 4.4.0
 */
function astra_single_post_entry_featured_image() {
        $post_type           = strval( get_post_type() );
        $featured_image_size = astra_get_option( 'ast-dynamic-single-' . $post_type . '-article-featured-image-size', 'large' );

        if ( apply_filters( 'astra_post_featured_image_condition', ( has_post_thumbnail() ) ) ) {
                do_action( 'astra_article_featured_image_before' );

                $output     = '';
                $post_thumb = apply_filters(
                        'astra_article_featured_image_markup',
                        get_the_post_thumbnail(
                                /** @psalm-suppress InvalidArgument */ // phpcs:ignore Generic.Commenting.DocComment.MissingShort
                                absint( astra_get_post_id() ),
                                /** @psalm-suppress InvalidArgument */ // phpcs:ignore Generic.Commenting.DocComment.MissingShort
                                apply_filters( 'astra_post_featured_image_default_size', $featured_image_size ),
                                apply_filters( 'astra_post_featured_image_itemprop', '' )
                        )
                );
                if ( '' != $post_thumb ) {
                        $featured_image_width = 'layout-1' === astra_get_option( 'ast-dynamic-single-' . $post_type . '-layout', 'layout-1' ) ? astra_get_option( 'ast-dynamic-single-' . $post_type . '-article-featured-image-width-type', 'wide' ) : '';
                        $output              .= '<div class="ast-single-post-featured-section post-thumb ast-article-image-container--' . esc_attr( $featured_image_width ) . '">';
                        $output              .= $post_thumb;
                        $output              .= '</div>';
                }

                $output = apply_filters( 'astra_featured_post_thumbnail', $output );
                echo wp_kses_post( $output );

                do_action( 'astra_article_featured_image_after' );
        }
}
// 後略

//スマートフォンを判別
function is_mobile(){
    $useragents = array(
        'iPhone', // iPhone
        'iPod', // iPod touch
        'Android.*Mobile', // 1.5+ Android *** Only mobile
        'Windows.*Phone', // *** Windows Phone
        'dream', // Pre 1.5 Android
        'CUPCAKE', // 1.5+ Android
        'blackberry9500', // Storm
        'blackberry9530', // Storm
        'blackberry9520', // Storm v2
        'blackberry9550', // Storm v2
        'blackberry9800', // Torch
        'webOS', // Palm Pre Experimental
        'incognito', // Other iPhone browser
        'webmate' // Other iPhone browser
    );
    $pattern = '/'.implode('|', $useragents).'/i';
    return preg_match($pattern, $_SERVER['HTTP_USER_AGENT']);
}

// アイキャッチ画像サイズの適正化（モバイル端末とそれ以外）
// 投稿ページ用
function optimize_post_thumbnail_default_size( $image_size ) {
        if( is_mobile() ) {
                $image_size = 'medium';
        } else {
                $image_size = 'full';
        }
        return $image_size;
}
add_filter( 'astra_post_thumbnail_default_size', 'optimize_post_thumbnail_default_size' );

// 固定ページ用
function optimize_featured_image_size( $featured_image_size ) {
        if( is_mobile() ) {
                $featured_image_size = 'medium';
        } else {
                $featured_image_size = 'full';
        }
        return $featured_image_size;
}
add_filter( 'astra_post_featured_image_default_size', 'optimize_featured_image_size' );