Place watermark image on other images (C#, ASP.Net)

How do I add a watermark image onto other images?

I’m able to place text on an image as a water mark but now I have an image that I’d like to put on there instead of the text. How do I do this in C#?

Just one more time to be specific, I have image X and I want to use it as a watermark symbol. I want this symbol to appear on all my image when shown on my website. So I will have image X watermarked on image Y and Z.

Here’s the code I currently have that creates the watermark:

public static void AddWaterMark(MemoryStream ms, string watermarkText, MemoryStream outputStream)
        {
            System.Drawing.Image img = System.Drawing.Image.FromStream(ms);
            Graphics gr = Graphics.FromImage(img);
            Font font = new Font("Tahoma", (float)40);
            Color color = Color.FromArgb(50, 241, 235, 105);
            double tangent = (double)img.Height / (double)img.Width;
            double angle = Math.Atan(tangent) * (180 / Math.PI);
            double halfHypotenuse = Math.Sqrt((img.Height * img.Height) + (img.Width * img.Width)) / 2;
            double sin, cos, opp1, adj1, opp2, adj2;

            for (int i = 100; i > 0; i--)
            {
                font = new Font("Tahoma", i, FontStyle.Bold);
                SizeF sizef = gr.MeasureString(watermarkText, font, int.MaxValue);

                sin = Math.Sin(angle * (Math.PI / 180));
                cos = Math.Cos(angle * (Math.PI / 180));
                opp1 = sin * sizef.Width;
                adj1 = cos * sizef.Height;
                opp2 = sin * sizef.Height;
                adj2 = cos * sizef.Width;

                if (opp1 + adj1 < img.Height && opp2 + adj2 < img.Width)
                    break;
                //
            }

            StringFormat stringFormat = new StringFormat();
            stringFormat.Alignment = StringAlignment.Center;
            stringFormat.LineAlignment = StringAlignment.Center;

            gr.SmoothingMode = SmoothingMode.AntiAlias;
            gr.RotateTransform((float)angle);
            gr.DrawString(watermarkText, font, new SolidBrush(color), new Point((int)halfHypotenuse, 0), stringFormat);

            img.Save(outputStream, ImageFormat.Jpeg);
        }

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

in the same place where you call gr.DrawString, you can also do gr.DrawImage(position, size, overlayImage). It helps if your image-to-overlay is loaded from a PNG file (with transparency) to produce the best quality.

Method 2

Here is another solution which uses GDI+

Creating a Watermarked Photograph with GDI+ for .NET

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0