/// <summary>
/// Private method to get the words.
/// </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="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)
{
if (pageLetters == null || pageLetters.Count() == 0)
{
return(new List <Word>());
}
TextDirection textDirection = pageLetters.ElementAt(0).TextDirection;
if (pageLetters.Any(x => textDirection != x.TextDirection))
{
throw new ArgumentException("NNWordExtractor.GetWords(): Mixed Text Direction.");
}
Func <IEnumerable <Letter>, IReadOnlyList <Letter> > orderFunc = l => l.OrderBy(x => x.GlyphRectangle.Left).ToList();
if (textDirection == TextDirection.Rotate180)
{
orderFunc = l => l.OrderByDescending(x => x.GlyphRectangle.Right).ToList();
}
else if (textDirection == TextDirection.Rotate90)
{
orderFunc = l => l.OrderByDescending(x => x.GlyphRectangle.Top).ToList();
}
else if (textDirection == TextDirection.Rotate270)
{
orderFunc = l => l.OrderBy(x => x.GlyphRectangle.Bottom).ToList();
}
Letter[] letters = pageLetters.ToArray();
var groupedIndexes = ClusteringAlgorithms.SimpleTransitiveClosure(letters,
distMeasure,
(l1, l2) => Math.Max((double)metric(l1), (double)metric(l2)) * 0.60,
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();
List <Word> words = new List <Word>();
for (int a = 0; a < groupedIndexes.Count(); a++)
{
words.Add(new Word(orderFunc(groupedIndexes[a].Select(i => letters[i]))));
}
return(words);
}
/// <summary>
/// Build lines via transitive closure.
/// </summary>
private static IEnumerable <TextLine> GetLines(List <Word> words, double maxDist, AngleBounds withinLine)
{
/***************************************************************************************************
* /!\ WARNING: Given how FindIndexNearest() works, if 'maxDist' > 'word Width', the algo might not
* work as the FindIndexNearest() function might pair the pivot with itself (the pivot's right point
* (distance = width) is closer than other words' left point).
* -> Solution would be to find more than one nearest neighbours. Use KDTree?
***************************************************************************************************/
TextDirection textDirection = words[0].TextDirection;
var groupedIndexes = ClusteringAlgorithms.SimpleTransitiveClosure(words, Distances.Euclidean,
(pivot, candidate) => maxDist,
pivot => pivot.BoundingBox.BottomRight, candidate => candidate.BoundingBox.BottomLeft,
pivot => true,
(pivot, candidate) =>
{
// Compare bottom right with bottom left for angle
var withinLineAngle = Distances.Angle(pivot.BoundingBox.BottomRight, candidate.BoundingBox.BottomLeft);
return(withinLineAngle >= withinLine.Lower && withinLineAngle <= withinLine.Upper);
}).ToList();
Func <IEnumerable <Word>, IReadOnlyList <Word> > orderFunc = l => l.OrderBy(x => x.BoundingBox.Left).ToList();
if (textDirection == TextDirection.Rotate180)
{
orderFunc = l => l.OrderByDescending(x => x.BoundingBox.Right).ToList();
}
else if (textDirection == TextDirection.Rotate90)
{
orderFunc = l => l.OrderByDescending(x => x.BoundingBox.Top).ToList();
}
else if (textDirection == TextDirection.Rotate270)
{
orderFunc = l => l.OrderBy(x => x.BoundingBox.Bottom).ToList();
}
for (var a = 0; a < groupedIndexes.Count; a++)
{
yield return(new TextLine(orderFunc(groupedIndexes[a].Select(i => words[i]))));
}
}
/// <summary>
/// Build blocks via transitive closure.
/// </summary>
private static IEnumerable <TextBlock> GetLinesGroups(TextLine[] lines, double maxDist)
{
/**************************************************************************************************
* We want to measure the distance between two lines using the following method:
* We check if two lines are overlapping horizontally.
* If they are overlapping, we compute the middle point (new X coordinate) of the overlapping area.
* We finally compute the Euclidean distance between these two middle points.
* If the two lines are not overlapping, the distance is set to the max distance.
*
* /!\ WARNING: Given how FindIndexNearest() works, if 'maxDist' > 'line Height', the algo won't
* work as the FindIndexNearest() function will always pair the pivot with itself (the pivot's top
* point (distance = height) is closer than other lines' top point).
* -> Solution would be to find more than one nearest neighbours. Use KDTree?
**************************************************************************************************/
Func <PdfLine, PdfLine, double> euclidianOverlappingMiddleDistance = (l1, l2) =>
{
var left = Math.Max(l1.Point1.X, l2.Point1.X);
var d = (Math.Min(l1.Point2.X, l2.Point2.X) - left);
if (d < 0)
{
return(double.MaxValue); // not overlapping -> max distance
}
return(Distances.Euclidean(
new PdfPoint(left + d / 2, l1.Point1.Y),
new PdfPoint(left + d / 2, l2.Point1.Y)));
};
var groupedIndexes = ClusteringAlgorithms.SimpleTransitiveClosure(lines,
euclidianOverlappingMiddleDistance,
(pivot, candidate) => maxDist,
pivot => new PdfLine(pivot.BoundingBox.BottomLeft, pivot.BoundingBox.BottomRight),
candidate => new PdfLine(candidate.BoundingBox.TopLeft, candidate.BoundingBox.TopRight),
pivot => true, (pivot, candidate) => true).ToList();
for (int a = 0; a < groupedIndexes.Count(); a++)
{
yield return(new TextBlock(groupedIndexes[a].Select(i => lines[i]).ToList()));
}
}