Merge pull request #186 from BobLd/dupOverlap

Implement DuplicateOverlappingTextProcessor

src/UglyToad.PdfPig.DocumentLayoutAnalysis/DuplicateOverlappingTextProcessor.cs

@@ -0,0 +1,94 @@
+namespace UglyToad.PdfPig.DocumentLayoutAnalysis
+{
+    using System.Collections.Generic;
+    using System.Linq;
+    using UglyToad.PdfPig.Content;
+    using UglyToad.PdfPig.PdfFonts;
+
+    /// <summary>
+    /// Checks if each letter is a duplicate and overlaps any other letter and remove the duplicate, and flag the remaining as bold.
+    /// <para>Logic inspired from PdfBox's PDFTextStripper class.</para>
+    /// </summary>
+    public static class DuplicateOverlappingTextProcessor
+    {
+        /// <summary>
+        /// Checks if each letter is a duplicate and overlaps any other letter and remove the duplicate, and flag the remaining as bold.
+        /// <para>Logic inspired from PdfBox's PDFTextStripper class.</para>
+        /// </summary>
+        /// <param name="letters">Letters to be processed.</param>
+        /// <returns>Letters with no duplicate overlapping.</returns>
+        public static IReadOnlyList<Letter> Get(IEnumerable<Letter> letters)
+        {
+            if (letters?.Any() != true)
+            {
+                return letters?.ToList();
+            }
+
+            var queue = new Queue<Letter>(letters);
+            var cleanLetters = new List<Letter>() { queue.Dequeue() }; // dequeue the first letter
+
+            while (queue.Count > 0)
+            {
+                var letter = queue.Dequeue();
+                bool addLetter = true;
+                int duplicatesOverlappingIndex = -1;
+
+                var duplicates = cleanLetters.Where(l => l.Value.Equals(letter.Value) && l.FontName.Equals(letter.FontName)); // do other checks?
+
+                if (duplicates.Any())
+                {
+                    double tolerance = letter.GlyphRectangle.Width / (letter.Value.Length == 0 ? 1 : letter.Value.Length) / 3.0;
+                    double minX = letter.GlyphRectangle.BottomLeft.X - tolerance;
+                    double maxX = letter.GlyphRectangle.BottomLeft.X + tolerance;
+                    double minY = letter.GlyphRectangle.BottomLeft.Y - tolerance;
+                    double maxY = letter.GlyphRectangle.BottomLeft.Y + tolerance;
+
+                    var duplicatesOverlapping = duplicates.FirstOrDefault(l => minX <= l.GlyphRectangle.BottomLeft.X &&
+                                                                               maxX >= l.GlyphRectangle.BottomLeft.X &&
+                                                                               minY <= l.GlyphRectangle.BottomLeft.Y &&
+                                                                               maxY >= l.GlyphRectangle.BottomLeft.Y);
+
+                    if (duplicatesOverlapping != default)
+                    {
+                        // duplicate overlapping letter was found, keeping the existing one and not adding this one.
+                        addLetter = false;
+                        duplicatesOverlappingIndex = cleanLetters.IndexOf(duplicatesOverlapping);
+                    }
+                }
+
+                if (addLetter)
+                {
+                    cleanLetters.Add(letter);
+                }
+                else if (duplicatesOverlappingIndex != -1)
+                {
+                    // TODO: need to update the bounding box
+                    // TODO: need to update bottom left/right
+                    // TODO: need to update width
+                    // update textSequence?
+
+                    // update font details to bold
+                    var fontDetails = new FontDetails(letter.Font.Name, true, letter.Font.Weight, letter.Font.IsItalic);
+
+                    var newLetter = new Letter(letter.Value,
+                        letter.GlyphRectangle,
+                        letter.StartBaseLine,
+                        letter.EndBaseLine,
+                        letter.Width,
+                        letter.FontSize,
+                        fontDetails,
+                        letter.Color,
+                        letter.PointSize,
+                        letter.TextSequence);
+
+                    // update markedContentStack?
+
+                    // update letters
+                    cleanLetters[duplicatesOverlappingIndex] = newLetter;
+                }
+            }
+
+            return cleanLetters;
+        }
+    }
+}

src/UglyToad.PdfPig/Content/Letter.cs

@@ -80,12 +80,12 @@
         /// <summary>
         /// Create a new letter to represent some text drawn by the Tj operator.
         /// </summary>
-        internal Letter(string value, PdfRectangle glyphRectangle, 
-            PdfPoint startBaseLine, 
+        public Letter(string value, PdfRectangle glyphRectangle,
+            PdfPoint startBaseLine,
             PdfPoint endBaseLine,
             double width,
             double fontSize,
-            FontDetails font, 
+            FontDetails font,
             IColor color,
             double pointSize,
             int textSequence)