Optional link rewriter func for HtmlRenderer

src/Markdig.Tests/Markdig.Tests.csproj

@@ -65,6 +65,7 @@
     <Compile Include="TestOrderedList.cs" />
     <Compile Include="TestPlainText.cs" />
     <Compile Include="TestPragmaLines.cs" />
+    <Compile Include="TestLinkRewriter.cs" />
     <Compile Include="TestRelativeUrlReplacement.cs" />
     <Compile Include="TestSourcePosition.cs" />
     <Compile Include="TestStringSliceList.cs" />

src/Markdig.Tests/TestLinkRewriter.cs

@@ -0,0 +1,44 @@
+using System;
+using System.IO;
+using Markdig.Parsers;
+using Markdig.Renderers;
+using NUnit.Framework;
+
+namespace Markdig.Tests
+{
+    public class TestLinkRewriter
+    {
+        [Test]
+        public void ReplacesRelativeLinks()
+        {
+            TestSpec(s => "abc" + s, "Link: [hello](/relative.jpg)", "abc/relative.jpg");
+            TestSpec(s => s + "xyz", "Link: [hello](relative.jpg)", "relative.jpgxyz");
+            TestSpec(null, "Link: [hello](relative.jpg)", "relative.jpg");
+            TestSpec(null, "Link: [hello](/relative.jpg)", "/relative.jpg");
+        }
+
+        [Test]
+        public void ReplacesRelativeImageSources()
+        {
+            TestSpec(s => "abc" + s, "Image: ![alt text](/image.jpg)", "abc/image.jpg");
+            TestSpec(s => "abc" + s, "Image: ![alt text](image.jpg \"title\")", "abcimage.jpg");
+            TestSpec(null, "Image: ![alt text](/image.jpg)", "/image.jpg");
+        }
+
+        public static void TestSpec(Func<string,string> linkRewriter, string markdown, string expectedLink)
+        {
+            var pipeline = new MarkdownPipelineBuilder().Build();
+
+            var writer = new StringWriter();
+            var renderer = new HtmlRenderer(writer);
+            renderer.LinkRewriter = linkRewriter;
+            pipeline.Setup(renderer);
+
+            var document = MarkdownParser.Parse(markdown, pipeline);
+            renderer.Render(document);
+            writer.Flush();
+
+            Assert.That(writer.ToString(), Contains.Substring("=\"" + expectedLink + "\""));
+        }
+    }
+}

src/Markdig/Renderers/HtmlRenderer.cs

@@ -80,6 +80,11 @@ public HtmlRenderer(TextWriter writer) : base(writer)
         /// </summary>
         public Uri BaseUrl { get; set; }
 
+        /// <summary>
+        /// Allows links to be rewritten
+        /// </summary>
+        public Func<string,string> LinkRewriter { get; set; }
+
         /// <summary>
         /// Writes the content escaped for HTML.
         /// </summary>
@@ -202,6 +207,11 @@ public HtmlRenderer WriteEscapeUrl(string content)
                 content = new Uri(BaseUrl, content).AbsoluteUri;
             }
 
+            if (LinkRewriter != null)
+            {
+                content = LinkRewriter(content);
+            }
+
             int previousPosition = 0;
             int length = content.Length;