How to add a Watermark Image to another Image?

Article
2009-10-15

Question

_{Thursday, October 15, 2009 8:16 AM}

Hello !

i try to mark my Images with another Image (watermark image). Now i stuck with the main function of my tool - the watermarking.

here is what i got:

public void Watermarking(string workingDir)
        {
            //set a working directory
            string m_WorkingDirectory = workingDir;

            try
            {
                //create a image object containing the photograph to watermark
                foreach (string imgPath in m_AllePhotoPfade)
                {
                    //Image imgPhoto = Image.FromFile(m_WorkingDirectory + "\\watermark_photo.jpg");
                    Image imgPhoto = Image.FromFile(imgPath);
                    int phWidth = imgPhoto.Width;
                    int phHeight = imgPhoto.Height;

                    //create a Bitmap the Size of the original photograph
                    Bitmap bmPhoto = new Bitmap(phWidth, phHeight, PixelFormat.Format24bppRgb);

                    bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);

                    //load the Bitmap into a Graphics object 
                    Graphics grPhoto = Graphics.FromImage(bmPhoto);

                    //create a image object containing the watermark
                    //Image imgWatermark = new Bitmap(m_WorkingDirectory + "\\watermark.jpg");
                    Image imgWatermark = new Bitmap(m_WaterMarkImage);
                    int wmWidth = imgWatermark.Width;
                    int wmHeight = imgWatermark.Height;

                    float opac = 0;
                    string sOpacity = cboOpacity.Text;

                    // Determine the opacity of the watermark
                    switch (sOpacity)
                    {
                        case "100%":
                            opac = 255; // 1 * 255
                            break;
                        case "75%":
                            opac = 191; // .75 * 255
                            break;
                        case "50%":
                            opac = 127; // .5 * 255
                            break;
                        case "25%":
                            opac = 64;  // .25 * 255
                            break;
                        case "10%":
                            opac = 25;  // .10 * 255
                            break;
                        default:
                            opac = 127; // default at 50%; .5 * 255
                            break;
                    }


                    int xPosOfWm = 0;
                    int yPosOfWm = 0;

                    if (optBottom.Checked && optLeft.Checked)
                    {
                         xPosOfWm = 10;
                         yPosOfWm = (phHeight - wmHeight) - 10;
                    }
                    if(optBottom.Checked && optRight.Checked)
                    {
                         xPosOfWm = ((phWidth - wmWidth) - 10);
                         yPosOfWm = (phHeight - wmHeight) - 10;
                    }
                    if(optTop.Checked && optLeft.Checked)
                    {
                            xPosOfWm = 10;
                            yPosOfWm = 10;
                    }
                    if(optTop.Checked && optRight.Checked)
                    {
                            xPosOfWm = ((phWidth - wmWidth) - 10);
                            yPosOfWm = 10;
                    }

                    #region MehrPositionen
                    //case ContentAlignment.BottomCenter:   
                    //    xPosOfWm = (phWidth/2) - (wmWidth/2);
                    //    yPosOfWm = (phHeight - wmHeight) - 10;
                    //    break;

                        //case ContentAlignment.MiddleCenter:
                        //    xPosOfWm = (phWidth/2) - (wmWidth/2);
                        //    yPosOfWm = (phHeight/2) - (wmHeight/2);
                        //    break;

                        //case ContentAlignment.MiddleLeft:
                        //    xPosOfWm = 10;
                        //    yPosOfWm = (phHeight/2) - (wmHeight/2);
                        //    break;

                        //case ContentAlignment.MiddleRight:
                        //    xPosOfWm = ((phWidth - wmWidth)-10);
                        //    yPosOfWm = (phHeight/2) - (wmHeight/2);
                        //    break;

                        //case ContentAlignment.TopCenter:
                        //    xPosOfWm = (phWidth/2) - (wmWidth/2);
                        //    yPosOfWm = 10;
                    //    break;
                    #endregion



                    //Set Opacity of Watermark
                    Image watermark = SetImgOpacity(imgWatermark, opac);

                    InsertTextCopyright(grPhoto, imgPhoto, phWidth, phHeight);
                    InsertWatermarkImage(bmPhoto, imgPhoto, phWidth, phHeight, wmWidth, wmHeight, watermark, grPhoto, m_WorkingDirectory);

                    MessageBox.Show("Alle Bilder mit Wasserzeichen wurden in das Verzeichnis: \r\n\r\n"
                                    +"- " + workingDir + "\r\n\r\n gespeichert.", "", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

as you can see i try also to set the oppacity of the image (search for "switch(sOpacity)" ). but now i stuck with this part - i try to create a new Image (watermark) and fill it with the result of eht Method "SetImageOpacity(imgWatermark, opac)".

now i dont know what is wrong - i guess is somekind with the flow in my software. so, it wont watermark my image with the watermark image.

Here is the Method "SetImgOpacity()" which i get from somewhere of the internet:

 public
 static
 Image SetImgOpacity(Image imgPic, float
 imgOpac)
      {
            Bitmap bmpPic = new
 Bitmap(imgPic.Width, imgPic.Height);
            Graphics gfxPic = Graphics.FromImage(bmpPic);

            ColorMatrix cmxPic = new
 ColorMatrix();
            cmxPic.Matrix33 = imgOpac;

            ImageAttributes iaPic = new
 ImageAttributes();
            iaPic.SetColorMatrix(cmxPic, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);

            gfxPic.DrawImage(imgPic, new
 Rectangle(0, 0, bmpPic.Width, bmpPic.Height), 0, 0, imgPic.Width, imgPic.Height, GraphicsUnit.Pixel, iaPic);
            gfxPic.Dispose();
            return
 bmpPic;
      }

Thanks for Help in any way !

regards,
streezer

All replies (5)

_{Saturday, October 17, 2009 5:30 PM ✅Answered | 1 vote}

You need to divide the imgOpac argument by 255. ColorMatrix coefficients are normally 0..1
Hans Passant.

_{Saturday, October 17, 2009 5:46 PM ✅Answered | 2 votes}

Use the TextureBrush class.

Edit: Forget the TextureBrush. It doesn't make watermarking any easier.

Strat a new Windows Forms application and replace the Form1 code with this:

using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
namespace WindowsFormsApplication1
{
  public partial class Form1 : Form
  {
    private PictureBox PicBox = new PictureBox();
    public Form1()
    {
      InitializeComponent();
      PicBox.Parent = this;
      PicBox.Dock = DockStyle.Fill;
      PicBox.SizeMode = PictureBoxSizeMode.Zoom;
      Bitmap Jpg = new Bitmap("C:\\Users\\Public\\Pictures\\Sample Pictures\\Desert Landscape.jpg");
      using (Bitmap Bmp = new Bitmap("C:\\Users\\Public\\Pictures\\Sample Pictures\\Dock.jpg"))
      {
        using (Bitmap WatermarkBmp = new Bitmap(Bmp, Bmp.Width / 4, Bmp.Height / 4))
        {
          PicBox.Image = WatermarkImage(Jpg, WatermarkBmp, new Point(400, 100), 0.5F);
        }
      }
    }
    public Bitmap WatermarkImage(Bitmap ImageToWatermark, Bitmap Watermark, Point WatermarkPosition, float Opacity)
    {
      using (Graphics G = Graphics.FromImage(ImageToWatermark))
      {
        using (ImageAttributes IA = new ImageAttributes())
        {
          ColorMatrix CM = new ColorMatrix();
          CM.Matrix33 = Opacity;
          IA.SetColorMatrix(CM);
          G.DrawImage(Watermark, new Rectangle(WatermarkPosition, Watermark.Size), 0, 0, Watermark.Width, Watermark.Height, GraphicsUnit.Pixel, IA);
        }
      }
      return ImageToWatermark;
    }
  }
}

It should work without modification on Vista. Select different pictures on XP.

_{Saturday, October 17, 2009 4:14 PM | 2 votes}

Hi Streezer,

Here is the sample windows application for you:

http://www.codeproject.com/KB/GDI-plus/watermarker.aspx

Using GDI and .NET:

http://www.codeproject.com/KB/GDI-plus/watermark.aspx

Regards,
Jai

_{Monday, October 19, 2009 12:03 PM}

thank you for the links - one project i've already known - but the other helped me a lot, escpecially with the position of the watermark image.

Thank you also for the code snippet - i try to insert all the informations now in my project...

it's very complex to do image editing in c# - so my opinion ;)

i'll write again if there's something new...

_{Friday, October 30, 2009 2:05 PM}

hey there,

I had no problems with the method from JohnWein but now i get one: "not valid paraemter".

i get this exception if i call the method like that:

Bitmap bmpWatermark = (Bitmap)imgWatermark;
Bitmap bmpImgPath = (Bitmap)Image.FromFile(imgPath);

completeImageWithWatermark = WatermarkImage(bmpImgPath, bmpWatermark, newPoint, opac);

the first image is getting watermarked - but then at the second one i get this message without meaning "not valid parameter".

anyone can help me solving that? any tipps?

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How to add a Watermark Image to another Image?

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