I have this ... but the Height (@mediaItem.umbracoHeight) and Width (@mediaItem.umbracoWidth) is empty?´
@mediaItem.umbracoFile is OK, I am using umbraco 4.7.2

@inherits umbraco.MacroEngines.DynamicNodeContext
@{
  @Html.Raw("<div id=\"s1\" class=\"pics\">")
 
  var parent = @Model.Up();
 
  if (parent != null) {
    foreach (var item in parent.Children.Where("Visible")) {
      dynamic mediaItem = @item.Media("gmp_foto");

      @Html.Raw("<div><img src=\"") 
      @mediaItem.umbracoFile 
      @Html.Raw("\" alt=\"")
      @item.GetProperty("gmp_title").Value
      @Html.Raw("\" Height=\"")
      @mediaItem.umbracoHeight
      @Html.Raw("\" Width=\"")
      @mediaItem.umbracoWidth
      @Html.Raw("\" /><center>")                                                      
      @item.GetProperty("gmp_title").Value
      @Html.Raw("</center><br>")
      if (item.GetProperty("gmp_galleriTekst").Value != "") {
        @item.GetProperty("gmp_galleriTekst").Value
        @Html.Raw("<br>")
      }
      @Html.Raw("</div>")
   }
  }