如何使用 PdfSharp 创建注释以突出显示现有 PDF 的文本

Question

我想知道是否可以使用PdfSharp在现有PDF中创建文本突出显示注释？

在 PdfSharp 文档中，我看到了PdfTextAnnotation&PdfRubberStampAnnotation的示例，但没有找到文档中提到的以下注释的示例代码。

PdfLineAnnotation, PdfSquareAnnotation, PdfCircleAnnotation, 
PdfMarkupAnnotation, PdfHighlightAnnotation, PdfUnderlineAnnotation,
PdfSquigglyAnnotation, PdfSoundAnnotation, PdfMovieAnnotation.

这些注释尚未在PdfSharp中实现吗？如果有人已经实现，请指出我的代码示例。

Answer 1

我也遇到了这样的问题，我在 PdfSharp 库中没有找到任何其他注释类型。所以我查看了PDF参考中的文章"12.5注释"。例如，它说要创建文本标记注释，开发人员需要指定Subtype和QuadPoints条目。请参阅下面的源代码。

namespace PdfSharp.Pdf.Annotations
{
using Extensions;
using System.Collections.Generic;
public class PdfHighlightAnnotation : PdfMarkupAnnotation
{
public PdfHighlightAnnotation()
{
Initialize();
}
public PdfHighlightAnnotation(PdfDocument document)
: base(document)
{
Initialize();
}
void Initialize()
{
Elements.SetName(Keys.Subtype, "/Highlight");
}
}
public class PdfStrikeOutAnnotation : PdfMarkupAnnotation
{
public PdfStrikeOutAnnotation()
{
Initialize();
}
public PdfStrikeOutAnnotation(PdfDocument document)
: base(document)
{
Initialize();
}
void Initialize()
{
Elements.SetName(Keys.Subtype, "/StrikeOut");
}
}
public abstract class PdfMarkupAnnotation : PdfAnnotation
{
protected PdfMarkupAnnotation()
{ }
protected PdfMarkupAnnotation(PdfDocument document)
: base(document)
{ }
public IEnumerable<PdfRectangle> Quadrilaterals
{
set {
var points = new PdfArray();
foreach (var r in value) {
points.Elements.AddRange(ToQuadPoints(r));
}
Elements.SetValue("/QuadPoints", points);
}
}
private IEnumerable<PdfItem> ToQuadPoints(PdfRectangle r)
{
// Conversion from PdfRectangle coordinates
//
// Y ^
//   |                     (X2 Y2)
//   |        +-----------+
//   |        |           |
//   |        |           |
//   |        +-----------+
//   | (X1 Y1)
//   |                              
//   +-----------------------------> 
//                                 X
// to QuadPoints coordinates (x1 y1 x2 y2 x3 y3 x4 y4)
//
// Y ^
//   | (x4 y4)             (x3 y3)
//   |        +-----------+
//   |        |           |
//   |        |           |
//   |        +-----------+
//   | (x1 y1)             (x2 y2)
//   |                              
//   +-----------------------------> 
//                                 X
//
return new List<PdfItem> { new PdfReal(r.X1), new PdfReal(r.Y1),
new PdfReal(r.X2), new PdfReal(r.Y1),
new PdfReal(r.X1), new PdfReal(r.Y2),
new PdfReal(r.X2), new PdfReal(r.Y2)};
}
}
}
namespace PdfSharp.Extensions
{
using PdfSharp.Pdf;
using System.Collections.Generic;
public static class ArrayElementsExtensions
{
public static void AddRange(this PdfArray.ArrayElements elements, IEnumerable<PdfItem> values)
{
foreach (var v in values) {
elements.Add(v);
}
}
}
}

Answer 2

在多次尝试并跟进pdfsharp论坛之后。我得到了解决方案。快乐编码！！ 原始问题和答案在这里

private static void AddAnnotation(XGraphics graphics, PdfPage page, double x, double y, double height, double width)
{
PdfSharp.Drawing.XRect rect = graphics.Transformer.WorldToDefaultPage(new XRect(new XPoint(x, y), new XSize(width, height)));
XRect annotrect = new XRect(new XPoint(x, y), new XSize(width, height));
// Create a PDF text annotation
PdfTextAnnotation textAnnot = new PdfTextAnnotation();
textAnnot.Title = "This is the title";
textAnnot.Subject = "This is the subject";
textAnnot.Contents = "This is the contents of the annotation.rThis is the 2nd line.";            
textAnnot.Rectangle = new PdfSharp.Pdf.PdfRectangle(rect);
// The following lines of code did the trick
textAnnot.Elements.Remove("/Subtype");
textAnnot.Elements.Add("/Subtype", new PdfLiteral("/Square"));
textAnnot.Elements.Add("/IC", new PdfLiteral("[0 0 0]"));
textAnnot.Elements.Add("/CA", new PdfLiteral("0"));
// Add the annotation to the page
page.Annotations.Add(textAnnot);
}