Merge pull request #187 from BobLd/dla-example-1

Add AdvancedTextExtraction example

examples/AdvancedTextExtraction.cs

@@ -0,0 +1,91 @@
+namespace UglyToad.Examples
+{
+    using PdfPig;
+    using System;
+    using System.Text;
+    using UglyToad.PdfPig.DocumentLayoutAnalysis.PageSegmenter;
+    using UglyToad.PdfPig.DocumentLayoutAnalysis.ReadingOrderDetector;
+    using UglyToad.PdfPig.DocumentLayoutAnalysis.WordExtractor;
+
+    public static class AdvancedTextExtraction
+    {
+        public static void Run(string filePath)
+        {
+            var sb = new StringBuilder();
+
+            using (var document = PdfDocument.Open(filePath))
+            {
+                foreach (var page in document.GetPages())
+                {
+                    // 0. Preprocessing
+                    var letters = page.Letters; // no preprocessing
+
+                    // 1. Extract words
+                    var wordExtractor = NearestNeighbourWordExtractor.Instance;
+                    var wordExtractorOptions = new NearestNeighbourWordExtractor.NearestNeighbourWordExtractorOptions()
+                    {
+                        Filter = (pivot, candidate) =>
+                        {
+                            // check if white space (default implementation of 'Filter')
+                            if (string.IsNullOrWhiteSpace(candidate.Value))
+                            {
+                                // pivot and candidate letters cannot belong to the same word 
+                                // if candidate letter is null or white space.
+                                // ('FilterPivot' already checks if the pivot is null or white space by default)
+                                return false;
+                            }
+
+                            // check for height difference
+                            var maxHeight = Math.Max(pivot.PointSize, candidate.PointSize);
+                            var minHeight = Math.Min(pivot.PointSize, candidate.PointSize);
+                            if (minHeight != 0 && maxHeight / minHeight > 2.0)
+                            {
+                                // pivot and candidate letters cannot belong to the same word 
+                                // if one letter is more than twice the size of the other.
+                                return false;
+                            }
+
+                            // check for colour difference
+                            var pivotRgb = pivot.Color.ToRGBValues();
+                            var candidateRgb = candidate.Color.ToRGBValues();
+                            if (!pivotRgb.Equals(candidateRgb))
+                            {
+                                // pivot and candidate letters cannot belong to the same word 
+                                // if they don't have the same colour.
+                                return false;
+                            }
+
+                            return true;
+                        }
+                    };
+
+                    var words = wordExtractor.GetWords(letters, wordExtractorOptions);
+
+                    // 2. Segment page
+                    var pageSegmenter = DocstrumBoundingBoxes.Instance;
+                    var pageSegmenterOptions = new DocstrumBoundingBoxes.DocstrumBoundingBoxesOptions()
+                    {
+
+                    };
+
+                    var textBlocks = pageSegmenter.GetBlocks(words, pageSegmenterOptions);
+
+                    // 3. Postprocessing
+                    var readingOrder = UnsupervisedReadingOrderDetector.Instance;
+                    var orderedTextBlocks = readingOrder.Get(textBlocks);
+
+                    // 4. Extract text
+                    foreach (var block in orderedTextBlocks)
+                    {
+                        sb.Append(block.Text.Normalize(NormalizationForm.FormKC)); // normalise text
+                        sb.AppendLine();
+                    }
+
+                    sb.AppendLine();
+                }
+            }
+
+            Console.WriteLine(sb.ToString());
+        }
+    }
+}

examples/Program.cs

@@ -42,6 +42,10 @@
                     ("Generate PDF/A-2A compliant file",
                     () => GeneratePdfA2AFile.Run(Path.Combine(filesDirectory, "..", "..", "Fonts", "TrueType", "Roboto-Regular.ttf"),
                         Path.Combine(filesDirectory, "smile-250-by-160.jpg")))
+                },
+                {7,
+                    ("Advance text extraction using layout analysis algorithms",
+                    () => AdvancedTextExtraction.Run(Path.Combine(filesDirectory, "ICML03-081.pdf")))
                 }
             };