Working with handwritten signatures

17 Mar 20229 minutes to read

PDF viewer allows you to include handwritten signatures in PDF documents and provides options to modify or remove the existing ones.

Enabling handwritten signature mode

Set the AnnotationMode property of the PDF viewer instance to HandwrittenSignature. After setting the signature mode the signature pad would appear on which the signature can be drawn. After drawing the signature, the Done button should be tapped to add the drawn signature to the PDF, you can use clear button to redraw the signature or close button to cancel signing.

C#
pdfViewer.AnnotationMode = AnnotationMode.HandwrittenSignature;

Disabling handwritten signature mode

Setting the AnnotationMode to None will disable the signature mode and would hide the signature pad.

C#
pdfViewer.AnnotationMode = AnnotationMode.None;

Adding handwritten signature programmatically

By AddAnnotation method, You can add the handwritten signatures programmatically. The created handwritten signature object passed as a parameter. The HandwrittenSignature instance acquires the InkPointsCollection, page number and position as the parameters.

The following code sample illustrates the adding of handwritten signature programmatically.

C#
var inkPointsCollection = new List<List<float>>();

inkPointsCollection.Add(new List<float> { 53f, 525f, 53f, 527f, 53f, 528f, 53f, 531f, 53f, 549f, 54f, 570f, 56f, 597f, 57f, 623f, 59f, 652f, 60f, 679f, 62f, 705f, 64f, 726f, 65f, 744f, 66f, 758f, 66f, 768f, 65f, 777f, 65f, 782f, 65f, 784f, 64f, 786f, 64f, 786f, 63f, 786f, 63f, 786f, 63f, 784f, 66f, 774f, 71f, 757f, 79f, 734f, 88f, 708f, 99f, 681f, 112f, 652f, 126f, 627f, 140f, 606f, 150f, 591f, 158f, 582f, 162f, 578f, 164f, 577f, 165f, 576f, 166f, 576f, 165f, 578f, 155f, 592f, 143f, 605f, 121f, 621f, 99f, 631f, 77f, 639f, 54f, 644f, 35f, 645f, 20f, 644f, 10f, 642f, 4f, 642f, 2f, 641f, 1f, 640f, 0f, 639f, 0f, 639f, 2f, 639f, 20f, 645f, 47f, 657f, 75f, 672f, 106f, 688f, 137f, 704f, 168f, 718f, 197f, 732f, 221f, 741f, 240f, 748f, 254f, 753f, 254f, 753f });

System.Drawing.Point position = new System.Drawing.Point(100, 100);
HandwrittenSignature signature = new HandwrittenSignature(inkPointsCollection, 1, position);
signature.Settings.Color = Color.Red;           

//Adds the  handwritten signature to the specified page 
pdfViewer.AddAnnotation(signature);

Select handwritten signature programmatically

By SelectAnnotation method, You can select the handwritten signature programmatically. The specified handwritten signature object passed as a parameter.

The following code sample illustrates the same.

C#
//Selects the specified handwritten signature 
pdfViewer.SelectAnnotation(signature);

NOTE

Once SelectAnnotation method is called and as long as the annotation stays selected, the SelectedAnnotation property will return the same instance as the parameter of this method.

Deselect handwritten signature programmatically

By DeselectAnnotation method, You can deselect the handwritten signature programmatically .The specified handwritten signature object passed as a parameter.

The following code sample illustrates the same.

C#
//Deselects the specified handwritten signature
pdfViewer.DeselectAnnotation(signature);

NOTE

There is no effect in calling DeselectAnnotation method, if the given annotation is not selected. Once this method is called, the SelectedAnnotation property will return null until any other annotation gets selected.

Customizing the appearance of handwritten signatures

You can customize the default values such as stroke color, opacity, and thickness of all signatures to be added. This will not affect the already added signatures.

Setting the default stroke color

You can set the default stroke color of handwritten signatures by using the SfPdfViewer.AnnotationSettings.HandwrittenSignature.Color property. Refer to the following code.

C#
pdfViewer.AnnotationSettings.HandwrittenSignature.Color = UIColor.Red;

Setting the default opacity

You can set the default opacity of handwritten signatures by using the SfPdfViewer.AnnotationSettings.HandwrittenSignature.Opacity property. Opacity value ranges from 0 to 1. Refer to the following code example.

C#
pdfViewer.AnnotationSettings.HandwrittenSignature.Opacity = 0.5f;

Setting the default thickness

You can set the thickness of handwritten signatures by using the SfPdfViewer.AnnotationSettings.HandwrittenSignature.Thickness property. Refer to the following code example.

C#
pdfViewer.AnnotationSettings.HandwrittenSignature.Thickness = 5;

Setting the default minimum size

By the SfPdfViewer.AnnotationSettings.HandwrittenSignature.MinimumSize property, You can set the minimum size to which the handwritten signatures could be resized.

Refer the following code example:

C#
//Sets the minimum size for the handwritten signatures
pdfViewer.AnnotationSettings.HandwrittenSignature.MinimumSize = new CGSize(10, 10);

Similarity with Ink annotations

The handwritten signatures are preserved as ink annotations in PdfViewer. However, on saving you can choose whether to preserve the signature as ink annotation or flatten it. This can be achieved using the pdfViewer.AnnotationSettings.HandwrittenSignature.FlattenSignatureOnSave property.

C#
pdfViewer.AnnotationSettings.HandwrittenSignature.FlattenSignatureOnSave = true;

NOTE

The default value of the property is true.

Events

Since the handwritten signature is preserved as ink annotation, the events for both handwritten signatures and ink annotations are same. The events supported by ink annotations are described in detail here.

When the common events occur, ink annotation and handwritten signature can be distinguished using the event argument’s IsChildSignature property. Also, the sender parameter will be of type InkAnnotation and HandwrittenSignature for the respective annotations. For brevity, only the InkSelected event is illustrated below.

C#
pdfViewer.InkSelected += PdfViewer_InkSelected;

private void PdfViewer_InkSelected(object sender, Syncfusion.SfPdfViewer.iOS.InkSelectedEventArgs args)
{
	if(args.IsSignature)
	{
		//The event occurred was raised by handwritten signature
		//The "sender" parameter is of type "HandwrittenSignature"
	}
	else
	{
		//The event occurred was raised by ink annotation
		//The "sender" parameter is of type "InkAnnotation"
	}
}

How to lock or unlock the handwritten signature?

To lock or unlock all the handwritten signature, set the IsLocked API to true or false respectively, and the following sample explains the same. But other annotation types can be moved, resized, removed or their attributes can be changed.

C#
//Disable the handwritten signature interaction such as move, resize, remove, and attributes changes.
pdfViewerControl.AnnotationSettings.HandwrittenSignature.IsLocked = true;

Interactions with handwritten signature types such as move, resize, remove or attribute changes will be allowed only if the SfPdfViewer.AnnotationSettings.IsLocked API is set to false. The following code prevents the unlocking of the handwritten signatures, although the IsLocked property of the handwritten signature is set to false.

C#
//Disable the handwritten signature interaction, though its 'IsLocked' property is set to ‘false’ .
pdfViewerControl.AnnotationSettings.IsLocked = true;
pdfViewerControl.AnnotationSettings.HandwrittenSignature.IsLocked = false;

How to enable or disable the handwritten signature selection?

To enable or disable the handwritten signature selection, set the Constraints API to AnnotationConstraints.Selectable or ~AnnotationConstraints.Selectable respectively, and the following sample explains the same. But other annotation types can be selected, moved, resized, removed or their attributes can be changed.

C#
//Disable the selection of handwritten signatures.
pdfViewerControl.AnnotationSettings.HandwrittenSignature.Constraints = ~AnnotationConstraints.Selectable;

Handwritten signature selection will be allowed only if the SfPdfViewer.AnnotationSettings.Constraints API is set to AnnotationConstraints.Selectable. The following code prevents the handwritten signatures selection, even though the Constraints property of the handwritten signature annotation is set to AnnotationConstraints.Selectable.

C#
//Disable the handwritten signature selection, though its 'Constraints' property is set to ‘AnnotationConstraints.Selectable’ 
pdfViewerControl.AnnotationSettings.Constraints= ~AnnotationConstraints.Selectable;
pdfViewerControl.AnnotationSettings.HandwrittenSignature.Constraints = AnnotationConstraints.Selectable;

How to get and set the name of the handwritten signatures?

The PDF Viewer allows the users to get and set the name of handwritten signatures through the Name API.

The following code sample explains modifying the name of the handwritten signature in the InkAdded event.

C#
private void PdfViewerControl_InkAdded(object sender, InkAddedEventArgs args)
{
   if(sender is HandwrittenSignature)
    {
     (sender as HandwrittenSignature).Name = "HandwrittenSignature1";
    }
}

NOTE

For illustration purposes, we have only provided the sample for modifying the name of the handwritten signature in the InkAdded event. But this can be done in all other events as well.