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Adding text watermark is very slow in .NET

Hi, I’m evaluating GroupDocs.Watermark .NET APIs for my company,
I noticed that adding watermarks to docx, xlsx, pptx files are very slow,
it takes about 20 seconds to add watermarks to a 20 pages 1.02MB pptx file.

I did a simple profile, it seems GroupDocs.Watermark.Watermarker.ctor() is the bottleneck:
image.png (15.3 KB)

My question:

  1. Is this normal?
  2. Is this because I’m using a trial version of the GroupDocs.Watermark product?
  3. What can I do to improve the performance of adding watermarks?


Please share following details and we’ll investigate this issue:

  • API version (e.g. 19.10, 20.4) that you’re evaluating
  • Sample code that you’re using to add watermark
  • Sample PPTX file

Thanks for the reply,

It seems to be Windows Defender’s fault, after disable Defender’s real-time scan,
the elapsed time dropped to 4.7 seconds.

class Program
        static void Main(string[] args)
                var file = @"Microsoft Sway.pptx";
                var fileName = Path.GetFileNameWithoutExtension(file);
                var ext = Path.GetExtension(file);

                var sw = Stopwatch.StartNew();

                using (Watermarker watermarker = new Watermarker(file))
                    TextWatermark watermark = new TextWatermark("Confidential", new Font("Arial", 24));
                    watermark.HorizontalAlignment = HorizontalAlignment.Center;
                    watermark.VerticalAlignment = VerticalAlignment.Center;
                    watermark.RotateAngle = -45;
                    watermark.SizingType = SizingType.ScaleToParentDimensions;
                    watermark.ScaleFactor = 1;
                    watermark.Opacity = 0.4;

                var elapsed = sw.ElapsedMilliseconds;
                Console.WriteLine($"Takes {elapsed} ms");
            catch (Exception)


We enabled Windows defender and the antivirus. It took 4-5 seconds. Please have a look at this screenshot.PNG (68.5 KB).

After more tests, this seems only happen on my development machine, and only on the first run.
I don’t think it is GroupDocs 's issue, closing it, thanks for the reply.

1 Like


You’re welcome.