An image watermark is usually a logo or sign that appears on the background of digital documents, indicating the copyright owner of the content. Watermarking your PDF document with an image can prevent your data from being reused or modified. This article demonstrates how to add an image watermark to PDF in C# and VB.NET using Spire.PDF for .NET.
Install Spire.PDF for .NET
To begin with, you need to add the DLL files included in the Spire.PDF for.NET package as references in your .NET project. The DLLs files can be either downloaded from this link or installed via NuGet.
- Package Manager
PM> Install-Package Spire.PDF
Add an Image Watermark to PDF
The following are the main steps to add an image watermark to a PDF document.
- Create a PdfDocument object, and load a sample PDF file using PdfDocument.LoadFromFile() method.
- Load an image file using Image.FromFile() method.
- Loop through the pages in the document, and get the specific page through PdfDocument.Pages[] property.
- Set the image as background/watermark image of the current page through PdfPageBase.BackgroundImage property. Set the image position and size through PdfPageBase.BackgroundRegion property.
- Save the document to a different PDF file using PdfDocument.SaveToFile() method.
- C#
- VB.NET
using Spire.Pdf;
using System.Drawing;
namespace AddImageWatermark
{
class Program
{
static void Main(string[] args)
{
//Create a PdfDocument object
PdfDocument document = new PdfDocument();
//Load a sample PDF document
document.LoadFromFile(@"C:\Users\Administrator\Desktop\sample.pdf");
//Load an image
Image image = Image.FromFile(@"C:\Users\Administrator\Desktop\logo.png");
//Get the image width and height
int imgWidth = image.Width;
int imgHeight = image.Height;
//Loop through the pages
for (int i = 0; i < document.Pages.Count; i++)
{
//Get the page width and height
float pageWidth = document.Pages[i].ActualSize.Width;
float pageHeight = document.Pages[i].ActualSize.Height;
//Set the background opacity
document.Pages[i].BackgroudOpacity = 0.3f;
//Set the background image of current page
document.Pages[i].BackgroundImage = image;
//Position the background image at the center of the page
Rectangle rect = new Rectangle((int)(pageWidth - imgWidth) / 2, (int)(pageHeight - imgHeight) / 2, imgWidth, imgHeight);
document.Pages[i].BackgroundRegion = rect;
}
//Save the document to file
document.SaveToFile("AddImageWatermark.pdf");
document.Close();
}
}
}
Imports Spire.Pdf
Imports System.Drawing
Namespace AddImageWatermark
Class Program
Shared Sub Main(ByVal args() As String)
'Create a PdfDocument object
Dim document As PdfDocument = New PdfDocument()
'Load a sample PDF document
document.LoadFromFile("C:\Users\Administrator\Desktop\sample.pdf")
'Load an image
Dim image As Image = Image.FromFile("C:\Users\Administrator\Desktop\logo.png")
'Get the image width and height
Dim imgWidth As Integer = image.Width
Dim imgHeight As Integer = image.Height
'Loop through the pages
Dim i As Integer
For i = 0 To document.Pages.Count- 1 Step i + 1
'Get the page width and height
Dim pageWidth As single = document.Pages(i).ActualSize.Width
Dim pageHeight As single = document.Pages(i).ActualSize.Height
'Set the background opacity
document.Pages(i).BackgroudOpacity = 0.3f
'Set the background image of current page
document.Pages(i).BackgroundImage = image
'Position the background image at the center of the page
Dim rect As Rectangle = New Rectangle(CType((pageWidth - imgWidth) / 2,(Integer)(pageHeight - imgHeight) / 2,imgWidth,imgHeight, Integer))
document.Pages(i).BackgroundRegion = rect
Next
'Save the document to file
document.SaveToFile("AddImageWatermark.pdf")
document.Close()
End Sub
End Class
End Namespace
Apply for a Temporary License
If you'd like to remove the evaluation message from the generated documents, or to get rid of the function limitations, please request a 30-day trial license for yourself.
