Enhancing NearestNeighbourWordExtractor

- Making the code easier to read
- Using 20% of Width instead of 60%
- Making DefaultWordExtractor public

src/UglyToad.PdfPig.Tests/PublicApiScannerTests.cs

@@ -215,6 +215,7 @@
                 "UglyToad.PdfPig.Tokens.StreamToken",
                 "UglyToad.PdfPig.Tokens.StringToken",
                 "UglyToad.PdfPig.Util.IWordExtractor",
+                "UglyToad.PdfPig.Util.DefaultWordExtractor",
                 "UglyToad.PdfPig.Writer.PdfDocumentBuilder",
                 "UglyToad.PdfPig.Writer.PdfPageBuilder",
                 "UglyToad.PdfPig.Writer.TokenWriter",

src/UglyToad.PdfPig/DocumentLayoutAnalysis/NearestNeighbourWordExtractor .cs

@@ -26,34 +26,39 @@ namespace UglyToad.PdfPig.DocumentLayoutAnalysis
         {
             List<Word> wordsH = GetWords(
                 letters.Where(l => l.TextDirection == TextDirection.Horizontal),
-                l => l.GlyphRectangle.Width, Distances.Manhattan)
+                (l1, l2) => Math.Max((double)(l1.GlyphRectangle.Width), (double)(l2.GlyphRectangle.Width)) * 0.2, 
+                Distances.Manhattan)
                 .OrderByDescending(x => x.BoundingBox.Bottom)
                 .ThenBy(x => x.BoundingBox.Left).ToList();
 
             List<Word> words180 = GetWords(
                 letters.Where(l => l.TextDirection == TextDirection.Rotate180),
-                l => l.GlyphRectangle.Width, Distances.Manhattan)
+                (l1, l2) => Math.Max((double)(l1.GlyphRectangle.Width), (double)(l2.GlyphRectangle.Width)) * 0.2,
+                Distances.Manhattan)
                 .OrderBy(x => x.BoundingBox.Top)
                 .ThenByDescending(x => x.BoundingBox.Right).ToList();
             wordsH.AddRange(words180);
 
             List<Word> words90 = GetWords(
                 letters.Where(l => l.TextDirection == TextDirection.Rotate90),
-                l => l.GlyphRectangle.Height, Distances.Manhattan)
+                (l1, l2) => Math.Max((double)(l1.GlyphRectangle.Height), (double)(l2.GlyphRectangle.Height)) * 0.2,
+                Distances.Manhattan)
                 .OrderByDescending(x => x.BoundingBox.Left)
                 .ThenBy(x => x.BoundingBox.Top).ToList();
             wordsH.AddRange(words90);
 
             List<Word> words270 = GetWords(
                 letters.Where(l => l.TextDirection == TextDirection.Rotate270),
-                l => l.GlyphRectangle.Height, Distances.Manhattan)
+                (l1, l2) => Math.Max((double)(l1.GlyphRectangle.Height), (double)(l2.GlyphRectangle.Height)) * 0.2,
+                Distances.Manhattan)
                 .OrderBy(x => x.BoundingBox.Right)
                 .ThenByDescending(x => x.BoundingBox.Bottom).ToList();
             wordsH.AddRange(words270);
 
             List<Word> wordsU = GetWords(
                 letters.Where(l => l.TextDirection == TextDirection.Unknown),
-                l => l.GlyphRectangle.Width, Distances.Manhattan)
+                (l1, l2) => Math.Max((double)(l1.GlyphRectangle.Width), (double)(l2.GlyphRectangle.Width)) * 0.2,
+                Distances.Manhattan)
                 .OrderByDescending(x => x.BoundingBox.Bottom)
                 .ThenBy(x => x.BoundingBox.Left).ToList();
             wordsH.AddRange(wordsU);
@@ -66,12 +71,12 @@ namespace UglyToad.PdfPig.DocumentLayoutAnalysis
         /// </summary>
         /// <param name="pageLetters">The letters in the page, they must have
         /// the same text directions.</param>
-        /// <param name="metric">The letter's metric to use in the minimum distance
-        /// between 2 letters, e.g. GlyphRectangle.Width or GlyphRectangle.Height.</param>
+        /// <param name="maxDistanceFunction">The function that determines the maximum distance between two Letters,
+        /// e.g. Max(GlyphRectangle.Width) x 20%.</param>
         /// <param name="distMeasure">The distance measure between two start and end base line points,
         /// e.g. the Manhattan distance.</param>
         private List<Word> GetWords(IEnumerable<Letter> pageLetters,
-            Func<Letter, decimal> metric, Func<PdfPoint, PdfPoint, double> distMeasure)
+            Func<Letter, Letter, double> maxDistanceFunction, Func<PdfPoint, PdfPoint, double> distMeasure)
         {
             if (pageLetters == null || pageLetters.Count() == 0) return new List<Word>();
             TextDirection textDirection = pageLetters.ElementAt(0).TextDirection;
@@ -98,8 +103,7 @@ namespace UglyToad.PdfPig.DocumentLayoutAnalysis
             Letter[] letters = pageLetters.ToArray();
 
             var groupedIndexes = ClusteringAlgorithms.SimpleTransitiveClosure(letters,
-                distMeasure,
-                (l1, l2) => Math.Max((double)metric(l1), (double)metric(l2)) * 0.60,
+                distMeasure, maxDistanceFunction,
                 l => l.EndBaseLine, l => l.StartBaseLine,
                 l => !string.IsNullOrWhiteSpace(l.Value),
                 (l1, l2) => string.Equals(l1.FontName, l2.FontName, StringComparison.OrdinalIgnoreCase) && !string.IsNullOrWhiteSpace(l2.Value)).ToList();

src/UglyToad.PdfPig/Util/DefaultWordExtractor.cs

@@ -5,8 +5,15 @@
     using System.Linq;
     using Content;
 
-    internal class DefaultWordExtractor : IWordExtractor
+    /// <summary>
+    /// Default Word Extractor.
+    /// </summary>
+    public class DefaultWordExtractor : IWordExtractor
     {
+        /// <summary>
+        /// Gets the words.
+        /// </summary>
+        /// <param name="letters">The letters in the page.</param>
         public IEnumerable<Word> GetWords(IReadOnlyList<Letter> letters)
         {
             var lettersOrder = letters.OrderByDescending(x => x.Location.Y)
@@ -99,6 +106,9 @@
             return new Word(letters.ToList());
         }
 
+        /// <summary>
+        /// Create an instance of Default Word Extractor, <see cref="DefaultWordExtractor"/>.
+        /// </summary>
         public static IWordExtractor Instance { get; } = new DefaultWordExtractor();
 
         private DefaultWordExtractor()