Ink Annotation in PDF is a freehand graffiti-like shape; this type of annotation can arbitrarily specify the position and number of vertices of the shape, and through the specified vertices, the program will connect the points to draw a smooth curve. Below, we will introduce how to add this annotation in PDF through C# program code.

1. dll reference

Step 1 : Open “Solution Explorer” in Visual Studio – right mouse click “References” – “Manage NuGet Packages”.

Step 2 : Select “Browse” – enter the search content in the search box, select the search result, and click “Install”.

Step 3: Click “OK” – “Accept” in sequence, and then wait for the program to complete the installation.

Or, through official channels, download the package  Spire.PDF for .NET  to the local. After decompression, reference the Spire.Pdf.dll file in the BIN folder to the VS program.

 

2. Code example

When adding annotations, in addition to customizing the position and number of each point, you can also set ink color, line width, transparency, annotation content, name, etc. Here are the steps of the code implementation:

• Create an object of the PdfDocument class and load the PDF document through the PdfDocument.LoadFromFile(String fileName) method.
• Get the specified page of the PDF through the PdfDocument.Pages[int Index] property.
• Creates a collection of objects of type int, where the elements of the collection are the ink vertices.
• Create an instance of the PdfInkAnnotation class. And set the ink color, width, annotation content and other formats through the properties provided by this class.
• Call the PdfAnnotationCollection.Add(PdfAnnotation annotation) method provided by the PdfPageBase.AnnotationsWidget property to add annotations to the PDF.
• Finally, save the PDF document to the specified path through the PdfDocument.SaveToFile(string filename, FileFormat fileFormat) method.

C#

using Spire.Pdf;
 using Spire.Pdf.Annotations;
 using System.Collections.Generic;
 using System.Drawing;

namespace InkAnnotation
{
    class Program
    {
        static  void Main( string [] args)
        {
            // Load PDF document 
            PdfDocument pdf = new PdfDocument();
            pdf.LoadFromFile( " test.pdf " );

            // Get the first page 
            PdfPageBase pdfPage = pdf.Pages[ 0 ];

            // Set the ink coordinate point position 
            List< int []> inkList = new List< int []> ();           
             int [] intPoints = new  int []
            {
                370 , 700 ,
                 120 , 720 ,
                 110 , 760 ,
                 220 , 800 ,
                 270 , 790 ,
                 350 , 770 ,
                 350 , 670
            };
            inkList.Add(intPoints);
            // Add ink annotation to PDF page 
            PdfInkAnnotation inkannotation = new PdfInkAnnotation(inkList);
            inkannotation.Color = Color.MediumVioletRed;
            inkannotation.Border.Width = 6 ;
            inkannotation.Opacity = 0.5f ;
            inkannotation.Text = " This is an ink annotation. " ;
            inkannotation.Name = " Manager " ;     
            pdfPage.AnnotationsWidget.Add(inkannotation);

            // Save the document 
            Pdf.SaveToFile( " AddInkAnnotation.pdf " ,FileFormat.PDF);
            System.Diagnostics.Process.Start( " AddInkAnnotation.pdf " );
        }
    }
}

vb.net

Imports Spire.Pdf
 Imports Spire.Pdf.Annotations
 Imports System.Collections.Generic
 Imports System.Drawing

Namespace InkAnnotation
     Class Program
         Private  Shared  Sub Main(args As  String ())
             ' Load PDF document 
            Dim pdf As  New PdfDocument()
            pdf.LoadFromFile( " test.pdf " )

            ' Get the first page 
            Dim pdfPage As PdfPageBase = pdf.Pages( 0 )

            ' Set the ink coordinate point position 
            Dim inkList As  New List( Of  Integer ())()
             Dim intPoints As  Integer () = New  Integer () { 370 , 700 , 120 , 720 , 110 , 760 , _
                 220 , 800 , 270 , 790 , 350 , 770 , _
                 350 , 670 }
            inkList.Add(intPoints)
            ' Add ink annotation to PDF page 
            Dim inkannotation As  New PdfInkAnnotation(inkList)
            inkannotation.Color = Color.MediumVioletRed
            inkannotation.Border.Width = 6 
            inkannotation.Opacity = 0.5F _
            inkannotation.Text = " This is an ink annotation. " 
            inkannotation.Name = " Manager "
            pdfPage.AnnotationsWidget.Add(inkannotation)

            ' Save the document 
            pdf.SaveToFile( " AddInkAnnotation.pdf " , FileFormat.PDF)
         End Sub 
    End Class 
End Namespace

Annotation effect: