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- How to downscale all images in a PDF
- How to generate and export certificates
- How to downscale all images in a PDF
- Add Stamp to PDF
- How to reduce PDF file size
- How do I create graphics with Icc based colors
- Highlight fields in PDF
- Add a note to PDF
- Resize PDF pages
- Verify a custom digital PDF signature
- Extract glyph boxes from PDF
- Use TrueType font collections
- Layout text with MultilineTextShape
- Merge PDF files in C# .NET
- How do I extract page destinations from bookmarks?
- Clip PDF page content in C#
- Fill PDF form
- Extract glyphs and sort by reading order
- Add bookmarks to PDF
- How to scale content of PDF
- Create rectangles with rounded corners
- Create text with decorations
- Create layers in PDF and draw on each layer
- TIFF to PDF C#
- Crop content on a PDF page
- How to embed files in a PDF document
- Remove graphics from PDF
- Change the color inside a PDF
- Import FDF into PDF
- Flatten PDF form
- Digitally sign a PDF form in C# or VB.NET
- Vector graphics in PDF
- Translate PDF page content
- Extract graphics from PDF
- Determine the content bounding box
- Search text in PDF
- Convert PDF to plain text
- Flatten Markup Annotation
- Add text field to PDF
- Extract embedded files from PDF
- Extract images from PDF
- Add a Diagonal Watermark to PDF in C#
- Fit image to PDF page
- Add simple html text to PDF
- Add multiline text to a PDF document
- Add single-line text to PDF
- Create a new digitally signed PDF document
- PDF Viewer Preferences
- Change page orientation PDF
- Split PDF pages in C# and VB.NET
- Append two or more existing PDF files
- Determine if a PDF only contains images
- Add footer to PDF
- Convert SVG to PDF
- Fill in a PDF form using MVC
- Add hyperlink to PDF
- Rotate a PDF page
- Change the formatting of a numeric field
- How to mirror PDF pages and other shapes
- Fill in a template PDF document
- How to add autosized text to PDF
- Create formfields in PDF documents
- Export FDF from PDF form
- Add a link with an internal destination to PDF
- Remove PDF security settings
- Add a link to PDF with an external destination
- How to sign and verify updates to a PDF document
- Embed TrueType font
- How to create a tiling for shapes in PDF
- EMF to PDF as vector image
- EMF to PDF as raster image
- Replace field with image
- Add a rubber stamp annotation with a custom icon
- Create a text annotation in PDF with rich text
- Read and write meta data from PDF
- Create a custom signature handler to sign and verify PDF documents
- Download and convert image to PDF
- Add barcodes to PDF
- Use multiple licenses
- Disable submit button after submitting
Highlight fields in PDF
This code sample shows how to mark all fields in a PDF document.
Each field will be highlighted with a colored border. We will use a RectangleShape as the border. The color of the border depends on the type of a field.
C# code sample
// enumerate the pages
foreach (var page in document.Pages)
{
// enumerate the widgets
foreach (var widget in page.Widgets)
{
//create a highlight shape for each widget
var highlight = CreateHighlight(widget);
if (highlight == null) continue;
//add the highlight to the page
page.Overlay.Add(highlight);
}
}
' enumerate the pages
For Each page As var In document.Pages
' enumerate the widgets
For Each widget As var In page.Widgets
'create a highlight shape for each widget
Dim highlight = CreateHighlight(widget)
If highlight Is Nothing Then
Continue For
End If
'add the highlight to the page
page.Overlay.Add(highlight)
Next
Next
In CreateHighlight routine we create the RectangleShape. The simplest way to create rectangles with different colors is to use conditions(if..else..)
C# code sample
private static Shape CreateHighlight(Widget widget)
{
//create different pens for different field types
Pen pen;
if (widget.Field is TextField)
{
pen = new Pen(System.Drawing.Color.Red, 3);
}
else if (widget.Field is CheckBoxField)
{
pen = new Pen(System.Drawing.Color.Blue, 3);
}
else if (widget.Field is RadioButtonField)
{
pen = new Pen(System.Drawing.Color.Green, 3);
}
else if (widget.Field is ValueField)
{
pen = new Pen(System.Drawing.Color.Orange, 3);
}
else
{
pen = new Pen(System.Drawing.Color.Yellow, 3);
}
//create a rectangular highlighting
return new RectangleShape(widget.Left, widget.Bottom,
widget.Width, widget.Height, pen);
}
Private Shared Function CreateHighlight(widget As Widget) As Shape
'create different pens for different field types
Dim pen As Pen
If TypeOf widget.Field Is TextField Then
pen = New Pen(System.Drawing.Color.Red, 3)
ElseIf TypeOf widget.Field Is CheckBoxField Then
pen = New Pen(System.Drawing.Color.Blue, 3)
ElseIf TypeOf widget.Field Is RadioButtonField Then
pen = New Pen(System.Drawing.Color.Green, 3)
ElseIf TypeOf widget.Field Is ValueField Then
pen = New Pen(System.Drawing.Color.Orange, 3)
Else
pen = New Pen(System.Drawing.Color.Yellow, 3)
End If
'create a rectangular highlighting
Return New RectangleShape(widget.Left, widget.Bottom, widget.Width, widget.Height, pen)
End Function
Another way is to implement a custom field visitor inherited from the FieldVisitor class.
internal class MarkFieldVisitor : FieldVisitor
{
public override object Visit(TextField field, object argument)
{
//we passed the widget as argument;
var widget = argument as Widget;
var pen = new Pen(Color.Red, 3);
return CreateHighlight(widget, pen);
}
public override object Visit(CheckBoxField field, object argument)
{
//we passed the widget as argument;
var widget = argument as Widget;
var pen = new Pen(Color.Blue, 3);
return CreateHighlight(widget, pen);
}
public override object Visit(RadioButtonField field, object argument)
{
//we passed the widget as argument;
var widget = argument as Widget;
var pen = new Pen(Color.Green, 3);
return CreateHighlight(widget, pen);
}
public override object Visit(ValueField field, object argument)
{
//we passed the widget as argument;
var widget = argument as Widget;
var pen = new Pen(Color.Orange, 3);
return CreateHighlight(widget, pen);
}
public override object Visit(Field field, object argument)
{
//we passed the widget as argument;
var widget = argument as Widget;
var pen = new Pen(Color.Yellow, 3);
return CreateHighlight(widget, pen);
}
private static object CreateHighlight(Widget widget, Pen pen)
{
return new RectangleShape(widget.Left, widget.Bottom,
widget.Width, widget.Height, pen);
}
}
Friend Class MarkFieldVisitor
Inherits FieldVisitor
Public Overrides Function Visit(field As TextField, argument As Object) As Object
'we passed the widget as argument;
Dim widget = TryCast(argument, Widget)
Dim pen = New Pen(Color.Red, 3)
Return CreateHighlight(widget, pen)
End Function
Public Overrides Function Visit(field As CheckBoxField, argument As Object) As Object
'we passed the widget as argument;
Dim widget = TryCast(argument, Widget)
Dim pen = New Pen(Color.Blue, 3)
Return CreateHighlight(widget, pen)
End Function
Public Overrides Function Visit(field As RadioButtonField, argument As Object) As Object
'we passed the widget as argument;
Dim widget = TryCast(argument, Widget)
Dim pen = New Pen(Color.Green, 3)
Return CreateHighlight(widget, pen)
End Function
Public Overrides Function Visit(field As ValueField, argument As Object) As Object
'we passed the widget as argument;
Dim widget = TryCast(argument, Widget)
Dim pen = New Pen(Color.Orange, 3)
Return CreateHighlight(widget, pen)
End Function
Public Overrides Function Visit(field As Field, argument As Object) As Object
'we passed the widget as argument;
Dim widget = TryCast(argument, Widget)
Dim pen = New Pen(Color.Yellow, 3)
Return CreateHighlight(widget, pen)
End Function
Private Shared Function CreateHighlight(widget As Widget, pen As Pen) As Object
Return New RectangleShape(widget.Left, widget.Bottom, widget.Width, widget.Height, pen)
End Function
End Class
The visitor we can use in the CreateHighlight method:
private static Shape CreateHighlight(Widget widget)
{
var fieldVisitor = new MarkFieldVisitor();
return widget.Field.Accept(fieldVisitor, widget) as Shape;
}
Private Shared Function CreateHighlight(widget As Widget) As Shape
Dim fieldVisitor = New MarkFieldVisitor()
Return TryCast(widget.Field.Accept(fieldVisitor, widget), Shape)
End Function
The input PDF:
The result:

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