Add support for image sizing via titles in markdown (#398)

Introduced a feature to parse width and height from image titles using a regex pattern. Updated the markdown parser, tests, and docs to support and demonstrate inline image resizing with syntax like `=WxH` or `=W`. If height is omitted, it defaults to the width value.

Author: Mpdreamz

docs/syntax/images.md

@@ -39,10 +39,49 @@ Or, use the `image` directive.
 ## Inline images
 
 ```markdown
-Here is the same image used inline ![Elasticsearch](img/observability.png)
+Here is the same image used inline ![Elasticsearch](img/observability.png "elasticsearch =50%x50%")
 ```
 
-Here is the same image used inline ![Elasticsearch](img/observability.png)
+Here is the same image used inline ![Elasticsearch](img/observability.png "elasticsearch =50%x50%")
+
+
+### Inline image titles
+
+Titles are optional making this the minimal syntax required
+
+```markdown
+![Elasticsearch](img/observability.png)
+```
+
+Including a title can be done by supplying it as an optional argument.
+
+```markdown
+![Elasticsearch](img/observability.png "elasticsearch")
+```
+
+### Inline image sizing
+
+Inline images are supplied at the end through the title argument.
+
+This is done to maintain maximum compatibility with markdown parsers
+and previewers. 
+
+```markdown
+![alt](img.png "title =WxH")
+![alt](img.png "title =W")
+```
+
+`W` and `H` can be either an absolute number in pixels or a number followed by `%` to indicate relative sizing.
+
+If `H` is omitted `W` is used as the height as well.
+
+```markdown
+![alt](img.png "title =250x330")
+![alt](img.png "title =50%x40%")
+![alt](img.png "title =50%")
+```
+
+
 
 ### SVG 
 

src/Elastic.Markdown/Myst/InlineParsers/DiagnosticLinkInlineParser.cs

@@ -4,6 +4,7 @@
 
 using System.Collections.Immutable;
 using System.IO.Abstractions;
+using System.Text.RegularExpressions;
 using Elastic.Markdown.Diagnostics;
 using Elastic.Markdown.IO;
 using Elastic.Markdown.Myst.Comments;
@@ -12,6 +13,7 @@
 using Markdig.Parsers;
 using Markdig.Parsers.Inlines;
 using Markdig.Renderers;
+using Markdig.Renderers.Html;
 using Markdig.Syntax.Inlines;
 
 namespace Elastic.Markdown.Myst.InlineParsers;
@@ -33,6 +35,14 @@ public void Setup(MarkdownPipelineBuilder pipeline) =>
 	public void Setup(MarkdownPipeline pipeline, IMarkdownRenderer renderer) { }
 }
 
+internal partial class LinkRegexExtensions
+{
+
+	[GeneratedRegex(@"\s\=(?<width>\d+%?)(?:x(?<height>\d+%?))?$", RegexOptions.IgnoreCase, "en-US")]
+	public static partial Regex MatchTitleStylingInstructions();
+
+}
+
 public class DiagnosticLinkInlineParser : LinkInlineParser
 {
 	// See https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml for a list of URI schemes
@@ -41,6 +51,7 @@ public class DiagnosticLinkInlineParser : LinkInlineParser
 	public override bool Match(InlineProcessor processor, ref StringSlice slice)
 	{
 		var match = base.Match(processor, ref slice);
+
 		if (!match || processor.Inline is not LinkInline link)
 			return match;
 
@@ -49,9 +60,38 @@ public override bool Match(InlineProcessor processor, ref StringSlice slice)
 			return match;
 
 		ValidateAndProcessLink(processor, link, context);
+
+		ParseStylingInstructions(processor, link, context);
+
 		return match;
 	}
 
+
+	private void ParseStylingInstructions(InlineProcessor processor, LinkInline link, ParserContext context)
+	{
+		if (string.IsNullOrWhiteSpace(link.Title) || link.Title.IndexOf('=') < 0)
+			return;
+
+		var matches = LinkRegexExtensions.MatchTitleStylingInstructions().Match(link.Title);
+		if (!matches.Success)
+			return;
+
+		var width = matches.Groups["width"].Value;
+		if (!width.EndsWith("%"))
+			width += "px";
+		var height = matches.Groups["height"].Value;
+		if (string.IsNullOrEmpty(height))
+			height = width;
+		else if (!height.EndsWith("%"))
+			height += "px";
+		var title = link.Title[..matches.Index];
+
+		link.Title = title;
+		var attributes = link.GetAttributes();
+		attributes.AddProperty("width", width);
+		attributes.AddProperty("height", height);
+	}
+
 	private static bool IsInCommentBlock(LinkInline link) =>
 		link.Parent?.ParentBlock is CommentBlock;
 

tests/authoring/Inline/InlineImages.fs

@@ -28,3 +28,46 @@ type ``relative path to image`` () =
         markdown |> convertsToHtml """
             <p><img src="_static/img/observability.png" alt="Elasticsearch" /></p>
         """
+
+type ``supplying a tittle`` () =
+    static let markdown = Setup.Markdown """
+![Elasticsearch](_static/img/observability.png "Hello world")
+"""
+
+    [<Fact>]
+    let ``validate HTML: includes title`` () =
+        markdown |> convertsToHtml """
+            <p><img src="_static/img/observability.png" alt="Elasticsearch" title="Hello world" /></p>
+        """
+
+type ``supplying a tittle with width and height`` () =
+    static let markdown = Setup.Markdown """
+![o](obs.png "Title =250x400")
+"""
+
+    [<Fact>]
+    let ``validate HTML: does not include width and height in title`` () =
+        markdown |> convertsToHtml """
+            <p><img src="obs.png" width="250px" height="400px" alt="o" title="Title"/></p>
+        """
+
+type ``supplying a tittle with width and height in percentage`` () =
+    static let markdown = Setup.Markdown """
+![o](obs.png "Title =50%x40%")
+"""
+
+    [<Fact>]
+    let ``validate HTML: does not include width and height in title`` () =
+        markdown |> convertsToHtml """
+            <p><img src="obs.png" width="50%" height="40%" alt="o" title="Title"/></p>
+        """
+type ``supplying a tittle with width only`` () =
+    static let markdown = Setup.Markdown """
+![o](obs.png "Title =30%")
+"""
+
+    [<Fact>]
+    let ``validate HTML: sets height to width if not supplied`` () =
+        markdown |> convertsToHtml """
+            <p><img src="obs.png" width="30%" height="30%" alt="o" title="Title"/></p>
+        """