public static HtmlString ResponsiveImage(this SitecoreHelper sitecoreHelper, string fieldName, Item item = null, object parameters = null, ResponsiveSizes responsiveSizes = null)
        {
            if (item == null)
            {
                item = sitecoreHelper.CurrentItem;
            }
            if (responsiveSizes == null || Sitecore.Context.PageMode.IsPageEditorEditing)
            {
                return sitecoreHelper.Field(fieldName, item, parameters);
            }
            var baseMediaUrlOptions = MediaUrlOptionsHelper.ParseMediaUrlOptions(parameters);
            var mediaItem = GetMediaItem(fieldName, item);
            var src = GetUrl(mediaItem, baseMediaUrlOptions);
            if (responsiveSizes.Default != null)
            {
                src = GetUrl(mediaItem, responsiveSizes.Default.GetMediaUrlOptions(baseMediaUrlOptions));
            }
            var properties = MediaUrlOptionsHelper.ParseUnusedParameters(parameters).Aggregate(string.Empty, (current, s) => current + string.Format("{0}=\"{1}\" ", s.Key, s.Value));
            var html = new StringBuilder("<img " + properties);
            html.AppendFormat(" src=\"{0}\"", src);
            html.AppendFormat(" alt=\"{0}\"", mediaItem.Alt);

            if (responsiveSizes.Mobile != null)
            {
                html.AppendFormat(" data-responsimg-mobile=\"{0}\"", GetUrlsString(mediaItem, responsiveSizes.Mobile, baseMediaUrlOptions));
            }
            if (responsiveSizes.Tablet != null)
            {
                html.AppendFormat(" data-responsimg-tablet=\"{0}\"", GetUrlsString(mediaItem, responsiveSizes.Tablet, baseMediaUrlOptions));
            }
            if (responsiveSizes.Desktop != null)
            {
                html.AppendFormat(" data-responsimg-desktop=\"{0}\"", GetUrlsString(mediaItem, responsiveSizes.Desktop, baseMediaUrlOptions));
            }

            html.Append(" />");
            return new HtmlString(html.ToString());
        }
 public static HtmlString ResponsiveImage(this SitecoreHelper sitecoreHelper, string fieldName, object parameters = null, ResponsiveSizes responsiveSizes = null)
 {
     return ResponsiveImage(sitecoreHelper, fieldName, (Item)null, parameters, responsiveSizes);
 }