WordPress在上传后生成图像大小

Question

我使用此代码上传图片：

function Generate_Featured_Image( $image_url, $post_id  ){
    $upload_dir = wp_upload_dir();
    $image_data = file_get_contents($image_url);
    $filename = basename($image_url);
    if(wp_mkdir_p($upload_dir['path']))
      $file = $upload_dir['path'] . '/' . $filename;
    else
      $file = $upload_dir['basedir'] . '/' . $filename;
    file_put_contents($file, $image_data);

    $wp_filetype = wp_check_filetype($filename, null );
    $attachment = array(
        'post_mime_type' => $wp_filetype['type'],
        'post_title' => sanitize_file_name($filename),
        'post_content' => '',
        'post_status' => 'inherit'
    );
    $attach_id = wp_insert_attachment( $attachment, $file, $post_id );

    require_once(ABSPATH . 'wp-admin/includes/media.php');
    require_once(ABSPATH . 'wp-admin/includes/file.php');
    require_once(ABSPATH . 'wp-admin/includes/image.php');

    $attach_data = wp_generate_attachment_metadata( $attach_id, $file );
    $res1 = wp_update_attachment_metadata( $attach_id, $attach_data );
    $res2 = set_post_thumbnail( $post_id, $attach_id );
}

此代码为手动尺寸：

if(function_exists('add_theme_support')) {
    add_theme_support('post-thumbnails');
    add_image_size('post', 260, 380, true);
}

如果我是从wordpress管理员上传的，则post的大小必须正确

但是根据我的代码，post的大小无法显示原始大小