Add Links to Pdf Generation

src/UglyToad.PdfPig.Tests/Writer/PdfDocumentBuilderTests.cs

@@ -1295,6 +1295,78 @@ public void CanCreateDocumentWithOutline()
             }
         }
 
+        [Fact]
+        public void CanAddLinkToPage()
+        {
+            var builder = new PdfDocumentBuilder();
+            var page = builder.AddPage(PageSize.A4);
+            var font = builder.AddStandard14Font(Standard14Font.Helvetica);
+
+            var linkArea = new PdfRectangle(25, 690, 200, 720);
+            page.AddLink("https://github.com", linkArea);
+
+            var bytes = builder.Build();
+            WriteFile(nameof(CanAddLinkToPage), bytes);
+
+            using (var document = PdfDocument.Open(bytes))
+            {
+                Assert.Equal(1, document.NumberOfPages);
+                var page1 = document.GetPage(1);
+
+                var annotations = page1.GetAnnotations().ToList();
+                Assert.Single(annotations);
+
+                var linkAnnotation = annotations[0];
+                Assert.Equal(Annotations.AnnotationType.Link, linkAnnotation.Type);
+                Assert.Equal(linkArea, linkAnnotation.Rectangle);
+
+                // Verify the URI link target
+                Assert.NotNull(linkAnnotation.Action);
+                var uriAction = Assert.IsType<Actions.UriAction>(linkAnnotation.Action);
+                Assert.Equal("https://github.com", uriAction.Uri);
+            }
+        }
+
+        [Fact]
+        public void CanAddInternalLinkToPage()
+        {
+            var builder = new PdfDocumentBuilder();
+            var font = builder.AddStandard14Font(Standard14Font.Helvetica);
+
+            var page1 = builder.AddPage(PageSize.A4);
+            var page2 = builder.AddPage(PageSize.A4);
+
+            var linkArea = new PdfRectangle(25, 690, 200, 720);
+            var coordinates = new ExplicitDestinationCoordinates(25, 750);
+            var destination = new ExplicitDestination(1, ExplicitDestinationType.XyzCoordinates, coordinates);
+            page2.AddLink(destination, linkArea);
+
+            var bytes = builder.Build();
+            WriteFile(nameof(CanAddInternalLinkToPage), bytes);
+
+            using (var document = PdfDocument.Open(bytes))
+            {
+                Assert.Equal(2, document.NumberOfPages);
+
+                var page2Doc = document.GetPage(2);
+
+                var annotations = page2Doc.GetAnnotations().ToList();
+                Assert.Single(annotations);
+
+                var linkAnnotation = annotations[0];
+                Assert.Equal(Annotations.AnnotationType.Link, linkAnnotation.Type);
+                Assert.Equal(linkArea, linkAnnotation.Rectangle);
+
+                // Verify the link destination
+                Assert.NotNull(linkAnnotation.Action);
+                var goToAction = Assert.IsType<Actions.GoToAction>(linkAnnotation.Action);
+                Assert.Equal(1, goToAction.Destination.PageNumber);
+                Assert.Equal(ExplicitDestinationType.XyzCoordinates, goToAction.Destination.Type);
+                Assert.Equal(25, goToAction.Destination.Coordinates.Left);
+                Assert.Equal(750, goToAction.Destination.Coordinates.Top);
+            }
+        }
+
         private static void WriteFile(string name, byte[] bytes, string extension = "pdf")
         {
             try

src/UglyToad.PdfPig/Writer/LinkAnnotation.cs

@@ -0,0 +1,178 @@
+namespace UglyToad.PdfPig.Writer
+{
+    using UglyToad.PdfPig.Actions;
+    using UglyToad.PdfPig.Annotations;
+    using UglyToad.PdfPig.Core;
+    using UglyToad.PdfPig.Tokens;
+
+    /// <summary>
+    /// Represents a link annotation that can be added to a PDF page.
+    /// Link annotations provide clickable areas that can trigger actions such as navigating to another page or opening a URL.
+    /// </summary>
+    public class LinkAnnotation
+    {
+        /// <summary>
+        /// Gets the border style for the link annotation.
+        /// This is overwritten by the <see cref="AnnotationBorder"/> if both are provided.
+        /// </summary>
+        public AnnotationBorder? AnnotationBorder { get; }
+
+        /// <summary>
+        /// Gets the border style for the link annotation.
+        /// </summary>
+        public BorderStyle? Border { get; }
+
+        /// <summary>
+        /// Gets the width of the border for the link annotation.
+        /// </summary>
+        public int? BorderWidth { get; }
+
+        /// <summary>
+        /// Gets the rectangle defining the location and size of the link annotation on the page.
+        /// </summary>
+        public PdfRectangle Rect { get; }
+
+        /// <summary>
+        /// Gets the quadrilaterals defining the clickable regions of the link.
+        /// These are typically used to define precise clickable areas that may not be rectangular.
+        /// </summary>
+        public IReadOnlyList<QuadPointsQuadrilateral> QuadPoints { get; }
+
+        /// <summary>
+        /// Gets the action to be performed when the link is activated.
+        /// </summary>
+        public PdfAction Action { get; }
+
+        /// <summary>
+        /// Specifies the border style for a link annotation.
+        /// </summary>
+        public enum BorderStyle
+        {
+            /// <summary>
+            /// A solid border.
+            /// </summary>
+            Solid,
+
+            /// <summary>
+            /// A dashed border.
+            /// </summary>
+            Dashed,
+
+            /// <summary>
+            /// A simulated embossed border that appears to be raised above the surface of the page.
+            /// </summary>
+            Beveled,
+
+            /// <summary>
+            /// A simulated engraved border that appears to be recessed below the surface of the page.
+            /// </summary>
+            Inset,
+
+            /// <summary>
+            /// An underline border drawn along the bottom of the annotation rectangle.
+            /// </summary>
+            Underline,
+        }
+
+        /// <summary>
+        /// Creates a new <see cref="LinkAnnotation"/> instance.
+        /// </summary>
+        /// <param name="action">The action to be performed when the link is activated.</param>
+        /// <param name="rect">The rectangle defining the location and size of the link on the page.</param>
+        /// <param name="annotationBorder">The border style for the link annotation. Optional, overwritten by <see cref="Border"/>.</param>
+        /// <param name="borderStyle">The border style for the link annotation. Optional.</param>
+        /// <param name="borderWidth">The width of the border for the link annotation. Optional.</param>
+        /// <param name="quadPoints">The quadrilaterals defining the clickable regions. Optional.</param>
+        public LinkAnnotation(
+            PdfAction action,
+            PdfRectangle rect,
+            AnnotationBorder? annotationBorder = null,
+            BorderStyle? borderStyle = null,
+            int? borderWidth = null,
+            IReadOnlyList<QuadPointsQuadrilateral>? quadPoints = null)
+        {
+            Action = action;
+            Rect = rect;
+            AnnotationBorder = annotationBorder;
+            Border = borderStyle;
+            BorderWidth = borderWidth;
+            QuadPoints = quadPoints ?? new List<QuadPointsQuadrilateral>();
+        }
+
+        /// <summary>
+        /// Converts this link annotation to a PDF dictionary token representation.
+        /// </summary>
+        /// <returns>A <see cref="DictionaryToken"/> representing this link annotation in PDF format.</returns>
+        public DictionaryToken ToToken()
+        {
+            var dict = new Dictionary<NameToken, IToken>
+            {
+                [NameToken.Type] = NameToken.Annot,
+                [NameToken.Subtype] = NameToken.Link,
+                [NameToken.Rect] = new ArrayToken([
+                    new NumericToken(Rect.BottomLeft.X),
+                    new NumericToken(Rect.BottomLeft.Y),
+                    new NumericToken(Rect.TopRight.X),
+                    new NumericToken(Rect.TopRight.Y)
+                ]),
+            };
+
+            if (QuadPoints.Count > 0)
+            {
+                var quadPointsArray = new List<NumericToken>();
+                foreach (var quad in QuadPoints)
+                {
+                    foreach (var point in quad.Points)
+                    {
+                        quadPointsArray.Add(new NumericToken(point.X));
+                        quadPointsArray.Add(new NumericToken(point.Y));
+                    }
+                }
+
+                dict.Add(NameToken.Quadpoints, new ArrayToken(quadPointsArray));
+            }
+
+            if (AnnotationBorder != null)
+            {
+                var borderArray = new List<IToken>
+                {
+                    new NumericToken(AnnotationBorder.HorizontalCornerRadius),
+                    new NumericToken(AnnotationBorder.VerticalCornerRadius),
+                    new NumericToken(AnnotationBorder.BorderWidth),
+                };
+
+                if (AnnotationBorder.LineDashPattern != null && AnnotationBorder.LineDashPattern.Count > 0)
+                {
+                    var dashArray = new List<NumericToken>();
+                    foreach (var dash in AnnotationBorder.LineDashPattern)
+                    {
+                        dashArray.Add(new NumericToken(dash));
+                    }
+                    borderArray.Add(new ArrayToken(dashArray));
+                }
+                dict.Add(NameToken.Border, new ArrayToken(borderArray));
+            }
+
+            if (Border != null)
+            {
+                dict.Add(NameToken.Bs, new DictionaryToken(new Dictionary<NameToken, IToken>
+                {
+                    [NameToken.S] = Border switch
+                    {
+                        BorderStyle.Solid => NameToken.S,
+                        BorderStyle.Dashed => NameToken.D,
+                        BorderStyle.Beveled => NameToken.B,
+                        BorderStyle.Inset => NameToken.I,
+                        BorderStyle.Underline => NameToken.U,
+                        _ => NameToken.S,
+                    },
+                    [NameToken.W] = new NumericToken(BorderWidth ?? 1)
+                }));
+            }
+
+
+
+            return new DictionaryToken(dict);
+        }
+    }
+}

src/UglyToad.PdfPig/Writer/PdfPageBuilder.cs

@@ -16,6 +16,7 @@
     using Graphics.Operations.TextPositioning;
     using Graphics.Operations.TextShowing;
     using Graphics.Operations.TextState;
+    using Outline.Destinations;
     using Images;
     using PdfFonts;
     using Tokens;
@@ -94,7 +95,7 @@ public class PdfPageBuilder
         private IPageContentStream currentStream;
 
         // links to be resolved when all page references are available
-        internal readonly List<(DictionaryToken token, PdfAction action)>? links;
+        internal readonly List<(DictionaryToken token, PdfAction action)> links = [];
 
         // maps fonts added using PdfDocumentBuilder to page font names
         private readonly Dictionary<Guid, NameToken> documentFonts = new Dictionary<Guid, NameToken>();
@@ -827,6 +828,39 @@ public AddedImage AddPng(Stream pngStream, PdfRectangle placementRectangle = def
             return new AddedImage(reference.Data, png.Width, png.Height);
         }
 
+        /// <summary>
+        /// Adds a URL link annotation to the page at the specified rectangle area.
+        /// </summary>
+        /// <param name="url">The URL to link to</param>
+        /// <param name="linkArea">The rectangular area on the page that will be clickable</param>
+        /// <returns>This page builder for method chaining</returns>
+        public PdfPageBuilder AddLink(string url, PdfRectangle linkArea)
+        {
+            return AddLink(new LinkAnnotation(new UriAction(url), linkArea));
+        }
+
+        /// <summary>
+        /// Adds an internal document link annotation to the page at the specified rectangle area.
+        /// </summary>
+        /// <param name="destination">The destination within the current document to link to</param>
+        /// <param name="linkArea">The rectangular area on the page that will be clickable</param>
+        /// <returns>This page builder for method chaining</returns>
+        public PdfPageBuilder AddLink(ExplicitDestination destination, PdfRectangle linkArea)
+        {
+            return AddLink(new LinkAnnotation(new GoToAction(destination), linkArea));
+        }
+
+        /// <summary>
+        /// Adds a link annotation to the page.
+        /// </summary>
+        /// <param name="link">The link annotation to add</param>
+        /// <returns>This page builder for method chaining</returns>
+        public PdfPageBuilder AddLink(LinkAnnotation link)
+        {
+            links.Add((link.ToToken(), link.Action));
+            return this;
+        }
+
         /// <summary>
         /// Copy a page from unknown source to this page
         /// </summary>