Экспортировать CHART в TIFF из Excel

// For complete examples and data files, please go to https://github.com/aspose-cells-cloud/aspose-cells-cloud-dotnet/
    string format = "tiff";
    string objectType ="chart";
    LightCellsApi lightCellsApi =
        new LightCellsApi(Environment.GetEnvironmentVariable("ProductClientId"), Environment.GetEnvironmentVariable("ProductClientSecret"));
    IDictionary<string ,Stream> files = new  Dictionary<string ,Stream>();
    files.Add("Book1.xlsx" , File.OpenRead("Book1.xlsx"));
    files.Add("myDocument.xlsx", File.OpenRead("myDocument.xlsx"));
    var filesResult = lightCellsApi.PostExport(files, objectType, format);
    foreach (var file in filesResult.Files)
    {
        string v = file.FileContent;
        string filename = file.Filename;
        byte[] workbookData = System.Convert.FromBase64String(v);
        MemoryStream memoryStream = new MemoryStream(workbookData, 0, workbookData.Length);
        memoryStream.Seek(0, SeekOrigin.Begin);
        using (FileStream fileStream = File.Create( filename))
        {
            fileStream.Position = 0;
            memoryStream.CopyTo(fileStream);
            fileStream.Close();
        }
    }