Introduction
PDF specification defines many
annotation types suitable for various purposes, just to name a few: Link annotation,
Text annotation, Line, Square and Polygon annotations, Watermark annotation,
Free Text annotation etc.
Annotations are divided to
different subtypes to highlight their primary usage, e.g. Markup annotations
are used for literally doc’s text markup, while Widget annotations are used to
represent the appearance of fields and to manage user interactions in PDF
forms. Some annotations are neither Markup, nor Widgets like Link annotation
for example.
The code
/// <summary>
/// This program demonstrates how to create custom appearance
for FreeText annotation
/// using generated <see
cref="FixedContent"/>.
/// </summary>
class Program
{
static void Main(string[] args)
{
using (Stream inputStream = File.Open("../../docs/input.pdf",
FileMode.Open, FileAccess.ReadWrite),
outputStream = new FileStream("out.pdf", FileMode.Create, FileAccess.ReadWrite))
{
//
create new document
using (FixedDocument document = new FixedDocument(inputStream))
{
Page page = document.Pages[0];
//
register image resource to be used as background
// for custom cloud annotation
document.ResourceManager.RegisterResource(
new
Apitron.PDF.Kit.FixedLayout.Resources.XObjects.Image(
"cloud", "../../images/cloud.png", true));
// add
two identical annotations to demonstrate normal
// and rollover appearance
page.Annotations.Add(
CreateRectangularFreeTextAnnotation(
"Free text annotation created using Apitron PDF Kit",
50, 550, 200, 40));
page.Annotations.Add(
CreateRectangularFreeTextAnnotation(
"Free text annotation created using Apitron PDF
Kit",
50, 490, 200, 40));
//
add image based annotation looking like a cloud
page.Annotations.Add(
CreateCloudFreeTextAnnotation("Hmm...I'm also a FreeText annotation...",
350, 550, 200, 200));
//
save changed copy of the document
document.Save(outputStream);
}
}
Process.Start("out.pdf");
}
You can see that we add three annotations here – two
identical rectangular annotations to demonstrate the difference between normal
and rollover states, and one “cloud”-shaped annotation based on an image. The
rest of the code can be seen below and the complete code sample can be found in
our github
repository.
private static Annotation
CreateRectangularFreeTextAnnotation(string text,
double x, double y,
double width, double height)
{
//
create PDF annotation object
FreeTextAnnotation annotation =
new FreeTextAnnotation(
new Boundary(x, y, x + width, y + height),
AnnotationFlags.ReadOnly);
annotation.Title = "Apitron";
annotation.Intent = IntentStyle.FreeText;
// set
custom appearance for normal and rollover states.
// if
you remove the read-only flag from the annotation,
// Adobe
reader will change this appearance to new when clicked.
// If
custom appearance is set, it's used instead of default.
annotation.Appearance.Normal =
CreateNormalAppearance(text, width, height);
annotation.Appearance.Rollover =
CreateRolloverAppearance(text, width, height);
// set properties affecting default appearance to be used
as fallback
annotation.FontSize = 12;
annotation.BorderEffect = new AnnotationBorderEffect(
AnnotationBorderEffectStyle.NoEffect, 0);
annotation.Contents = string.Format("{0} - default",text);
// text
and border color
annotation.TextColor = RgbColors.Red.Components;
//
set background here if needed
annotation.Color = RgbColors.Green.Components;
return annotation;
}
/// <summary>
/// Creates a fixed content object that contains
/// drawing instructions for normal annotation state.
/// </summary>
private static FixedContent CreateNormalAppearance(string text, double width,
double height)
{
//
create fixed content object, set its unique ID using guid.
// this
object will be implicitly added to page resources using this ID.
FixedContent fixedContent = new FixedContent(Guid.NewGuid().ToString("N"),
new Boundary(0, 0, width, height));
// use
text block from flow layout API subset,
// to
quickly draw text in a fixed content container.
TextBlock textBlock = new TextBlock(string.Format("{0} - normal", text));
textBlock.Border = Border.Solid;
textBlock.BorderColor = RgbColors.Blue;
textBlock.Display = Display.Block;
textBlock.Color = RgbColors.White;
textBlock.Width = width;
textBlock.Height = height;
textBlock.Background = RgbColors.Green;
fixedContent.Content.AppendContentElement(textBlock,
width, height);
return fixedContent;
}
/// <summary>
/// Creates a fixed content object that contains
/// drawing instructions for rollover annotation state.
/// </summary>
private static FixedContent CreateRolloverAppearance(string text,
double width, double height)
{
//
create fixed content object, set its unique ID using guid.
// this
object will be implicitly added to page resources using this ID.
FixedContent fixedContent = new FixedContent(Guid.NewGuid().ToString("N"),
new Boundary(0, 0, width, height));
// use
text block from flow layout API subset,
// to
quickly draw text in a fixed content container.
TextBlock textBlock = new TextBlock(string.Format("{0} - rollover", text));
textBlock.Border = Border.Solid;
textBlock.BorderColor = RgbColors.Blue;
textBlock.Display = Display.Block;
textBlock.Color = RgbColors.Green;
textBlock.Width = width;
textBlock.Height = height;
textBlock.Background = RgbColors.Yellow;
fixedContent.Content.AppendContentElement(textBlock, width, height);
return fixedContent;
}
/// <summary>
/// Creates a fixed content object that contains
/// drawing instructions cloud-shaped annotation based on
image.
/// </summary>
private static Annotation CreateCloudFreeTextAnnotation(string text, double x, double y,
double width, double height)
{
FreeTextAnnotation annotation = new FreeTextAnnotation(
new Boundary(x, y, x + width, y + height),
AnnotationFlags.ReadOnly);
annotation.Title = "Apitron";
annotation.Intent = IntentStyle.FreeText;
// set
custom normal appearance,
// if
you change the annotation to be editable,
// then
Adobe reader will change this appearance to new when clicked
annotation.Appearance.Normal =
CreateNormalCloudAppearance(text, width, height);
return annotation;
}
/// <summary>
/// Creates a fixed content object that contains
/// drawing instructions for normal annotation state.
/// </summary>
private static FixedContent CreateNormalCloudAppearance(string text,double width,
double height)
{
//
create fixed content object, set its unique ID using guid.
// this
object will be implicitly added to page resources using this ID.
FixedContent fixedContent = new FixedContent(Guid.NewGuid().ToString("N"),
new Boundary(0, 0, width, height));
//
append image using its resource id defined in program entry fn.
fixedContent.Content.AppendImage("cloud", 0, 0,
width, height);
TextBlock textBlock = new TextBlock(text);
textBlock.Color = RgbColors.Black;
fixedContent.Content.Translate(40,
-65);
fixedContent.Content.AppendContentElement(textBlock,
width, height);
return fixedContent;
}
}
Resulting document looks as follows:
 |
Pic. 1 PDF document with Free Text
annotations added using Apitron PDF Kit
|
Summary
If you need a powerful tool for
working with PDF documents – Apitron
PDF Kit for .NET library is a perfect choice. It contains only managed
code, so it works with any CLR implementation including MONO and can be used to
create XAMARIN apps as well (e.g. you can target iOS and Android easily).
The cross-platform nature of the
product allows you to create apps for Windows, Windows Store and Windows Phone
(including Windows 10), Silverlight, ASP.NET, Azure-hosted web and worker roles,
and also any system where .NET apps can run.
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