Get Image Url from Picture Library Item

public string GetDummyImageUrl(object theItem, string pictureLibrary)
{
StringBuilder url = new StringBuilder();
SPWeb web = SPContext.Current.Site.RootWeb;
DummyIdeaPictures = string.IsNullOrEmpty(DummyIdeaPictures) ? "DummyIdeaPictures" : DummyIdeaPictures;
SPListItem listItem = web.Lists[DummyIdeaPictures].GetItemById(Convert.ToInt32(theItem));
url.Append(SPEncode.UrlEncodeAsUrl(listItem.Web.Url));
url.Append('/');
url.Append(SPEncode.UrlEncodeAsUrl(listItem.ParentList.RootFolder.Url));
url.Append('/');
string filename = listItem.File.Name;
ImageSize imageSize = ImageSize.Full;
if (imageSize == ImageSize.Full)
{
url.Append(SPEncode.UrlEncodeAsUrl(filename));
}
else
{
string basefilename = Path.GetFileNameWithoutExtension(filename);
string extension = Path.GetExtension(filename);
string dir = (imageSize == ImageSize.Thumbnail) ? "_t/" : "_w/";
url.Append(dir);
url.Append(SPEncode.UrlEncodeAsUrl(basefilename));
url.Append(SPEncode.UrlEncodeAsUrl(extension).Replace('.', '_'));
url.Append(".jpg");}
return url.ToString();
}


public enum ImageSize
{
Thumbnail,
Large,
Full
}