How to: Highlight Search Results in a PDF File

• Apr 18, 2022
• 4 minutes to read

This example shows how to highlight search results in a document. You can use PDF Graphics to draw filled rectangles around text or add annotations to highlight search results.

Use PDF Graphics

Create a RectangleF object around the search result. Use the PdfGraphics.FillRectangle method to draw a rectangle around search text. The PdfGraphics.AddToPageForeground method allows you apply filled rectangles to the page.

C#

public static void HighlightResult(PdfGraphics graphics, PdfTextSearchResults result, SolidBrush brush)
{
    for (int i = 0; i < result.Rectangles.Count; i++)
    {
        RectangleF rect = new RectangleF(new PointF((float)result.Rectangles[i].Left, (float)result.Page.CropBox.Height - (float)result.Rectangles[i].Top),
            new SizeF((float)result.Rectangles[i].Width, (float)result.Rectangles[i].Height));

        graphics.FillRectangle(brush, rect);
    }
    graphics.AddToPageForeground(result.Page, 72, 72);
}

VB.NET

Public Shared Sub HighlightResult(ByVal graphics As PdfGraphics, ByVal result As PdfTextSearchResults, ByVal brush As SolidBrush)
    For i As Integer = 0 To result.Rectangles.Count - 1
        Dim rect As New RectangleF(New PointF(CSng(result.Rectangles(i).Left), CSng(result.Page.CropBox.Height) - CSng(result.Rectangles(i).Top)), New SizeF(CSng(result.Rectangles(i).Width), CSng(result.Rectangles(i).Height)))

        graphics.FillRectangle(brush, rect)
    Next i
    graphics.AddToPageForeground(result.Page, 72, 72)
End Sub

Use Annotations

Call the PdfDocumentProcessor.AddTextMarkupAnnotation method to add an annotation to the search results. Use the PdfTextSearchResults.Rectangles property to access the document areas that contain search text. The PdfAnnotationData.Color property specifies the annotation color.

C#

public static void HighlightResult(PdfDocumentProcessor processor, PdfTextSearchResults result)
{
    for (int i = 0; i < result.Rectangles.Count; i++)
    {
        PdfTextMarkupAnnotationData annotation = 
        processor.AddTextMarkupAnnotation(result.PageNumber, result.Rectangles[i], PdfTextMarkupAnnotationType.Highlight);
        if (annotation != null)
        {
            annotation.Color = new PdfRGBColor(0.2, 0.6, 0);
        }
    }
}

VB.NET

Public Shared Sub HighlightResult(ByVal processor As PdfDocumentProcessor, ByVal result As PdfTextSearchResults)
    For i As Integer = 0 To result.Rectangles.Count - 1
        Dim annotation As PdfTextMarkupAnnotationData = 
        processor.AddTextMarkupAnnotation(result.PageNumber, result.Rectangles(i), PdfTextMarkupAnnotationType.Highlight)
        If annotation IsNot Nothing Then
            annotation.Color = New PdfRGBColor(0.2, 0.6, 0)
        End If
    Next i
End Sub

Search and Highlight Text

The code example below shows how to use the PdfDocumentProcessor.FindText method to search text. (If you wish to highlight the results, you can also use the HighlightResult method - as described above.)

View Example

Program.cs

using DevExpress.Pdf;
using System.Drawing;

class Program {
    static void Main(string[] args) {
        // Create a PDF document processor.
        using (PdfDocumentProcessor documentProcessor = new PdfDocumentProcessor()) {
            // Define search words
            string[] words = { "Get", "DX-RX809", "HD", "DX-B5000" };

            // Load a PDF document
            documentProcessor.LoadDocument(@"..\..\Document.pdf");

            // Specify search parameters
            PdfTextSearchParameters searchParameters = new PdfTextSearchParameters();
            searchParameters.CaseSensitive = true;
            searchParameters.WholeWords = true;

            // Comment the following using statement if you use annotations
            using (var brush = new SolidBrush(Color.FromArgb(130, 55, 155, 255)))

            // Get search results from the FindText method call
            // with search text and search parameters
            PdfTextSearchResults result = documentProcessor.FindText(word, searchParameters);
                foreach (string word in words) {
                    // Highlight the result
                    while (result.Status == PdfTextSearchStatus.Found) {
                        using (PdfGraphics graphics = documentProcessor.CreateGraphics())
                        {
                            HighlightResult(graphics, result, brush);
                        }
                    // Use this method call to add annotations:
                    // HighlightResult(documentProcessor, result);
                    result = documentProcessor.FindText(word, searchParameters);
                    }
                }
            // Save the document
            documentProcessor.SaveDocument(@"..\..\Result.pdf");
        }
    }
}

Program.vb

Imports DevExpress.Pdf
Imports System.Drawing

Friend Class Program
    Shared Sub Main(ByVal args() As String)
        ' Create a PDF document processor.
        Using documentProcessor As New PdfDocumentProcessor()
            ' Define search words
            Dim words() As String = { "Get", "DX-RX809", "HD", "DX-B5000" }

            ' Load a PDF document
            documentProcessor.LoadDocument("..\..\Document.pdf")

            ' Specify search parameters
            Dim searchParameters As New PdfTextSearchParameters()
            searchParameters.CaseSensitive = True
            searchParameters.WholeWords = True

            ' Comment the following using statement if you use annotations
            Using brush = New SolidBrush(Color.FromArgb(130, 55, 155, 255))

            ' Get the search results from the FindText method call with search text and search parameters
            Dim result As PdfTextSearchResults = documentProcessor.FindText(word, searchParameters)
            End Using
                For Each word As String In words
                    ' Highlight the result
                    Do While result.Status = PdfTextSearchStatus.Found
                        Using graphics As PdfGraphics = documentProcessor.CreateGraphics()
                            HighlightResult(graphics, result, brush)
                        End Using
                    ' Use this method call to add annotations:
                    'HighlightResult(documentProcessor, result);
                    result = documentProcessor.FindText(word, searchParameters)
                    Loop
                Next word
            ' Save the document
            documentProcessor.SaveDocument("..\..\Result.pdf")
        End Using
    End Sub
End Class