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1   /**
2    * Copyright (c) 2011, The University of Southampton and the individual contributors.
3    * All rights reserved.
4    *
5    * Redistribution and use in source and binary forms, with or without modification,
6    * are permitted provided that the following conditions are met:
7    *
8    *   * 	Redistributions of source code must retain the above copyright notice,
9    * 	this list of conditions and the following disclaimer.
10   *
11   *   *	Redistributions in binary form must reproduce the above copyright notice,
12   * 	this list of conditions and the following disclaimer in the documentation
13   * 	and/or other materials provided with the distribution.
14   *
15   *   *	Neither the name of the University of Southampton nor the names of its
16   * 	contributors may be used to endorse or promote products derived from this
17   * 	software without specific prior written permission.
18   *
19   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
20   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
21   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
22   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
23   * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
24   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
25   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
26   * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29   */
30  package org.openimaj.image.text.extraction.swt;
31  
32  import java.util.ArrayList;
33  import java.util.Collections;
34  import java.util.Comparator;
35  import java.util.List;
36  
37  import org.openimaj.image.processing.threshold.OtsuThreshold;
38  import org.openimaj.util.pair.FloatFloatPair;
39  
40  /**
41   * This class models a candidate word (a collection of letter candidates with a
42   * consistent inter-character spacing) from the {@link SWTTextDetector}.
43   * 
44   * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
45   * 
46   */
47  public class WordCandidate extends Candidate {
48  	/**
49  	 * The line to which this word belongs
50  	 */
51  	protected LineCandidate line;
52  
53  	/**
54  	 * The letters in this word
55  	 */
56  	protected List<LetterCandidate> letters = new ArrayList<LetterCandidate>();
57  
58  	protected static List<WordCandidate> extractWords(LineCandidate line, SWTTextDetector.Options options) {
59  		final List<WordCandidate> words = new ArrayList<WordCandidate>();
60  
61  		// sort the letters
62  		Collections.sort(line.letters, new Comparator<LetterCandidate>() {
63  			@Override
64  			public int compare(LetterCandidate o1, LetterCandidate o2) {
65  				return o1.centroid.x - o2.centroid.x;
66  			}
67  		});
68  
69  		// Collect inter-word spacings
70  		final float[] spacings = new float[line.letters.size() - 1];
71  
72  		float mean = 0;
73  		int rng = 0;
74  		for (int i = 1; i < line.letters.size(); i++) {
75  			final LetterCandidate left = line.letters.get(i - 1);
76  			final LetterCandidate right = line.letters.get(i);
77  
78  			spacings[i - 1] = Math.max(0,
79  					right.getRegularBoundingBox().x
80  							- (left.getRegularBoundingBox().x + left.getRegularBoundingBox().width));
81  			mean += spacings[i - 1];
82  
83  			if (spacings[i - 1] >= rng)
84  				rng = (int) (spacings[i - 1] + 1);
85  		}
86  		mean /= spacings.length;
87  
88  		// use Otsu's method to find the optimal threshold
89  		final FloatFloatPair threshVar = OtsuThreshold.calculateThresholdAndVariance(spacings, rng);
90  		final float threshold = threshVar.first;
91  		final float variance = threshVar.second;
92  
93  		// System.out.println(Math.sqrt(variance) / mean + " " + variance + " "
94  		// + threshold);
95  		// if the variance is sufficiently high to suggest multiple words
96  		if (Math.sqrt(variance) > mean * options.wordBreakdownRatio)
97  		{
98  			WordCandidate word = new WordCandidate();
99  			word.line = line;
100 			word.letters.add(line.letters.get(0));
101 			words.add(word);
102 			for (int i = 0; i < spacings.length; i++) {
103 				if (spacings[i] > threshold) {
104 					word = new WordCandidate();
105 					words.add(word);
106 				}
107 				word.letters.add(line.letters.get(i + 1));
108 			}
109 		} else {
110 			final WordCandidate word = new WordCandidate();
111 			word.line = line;
112 			word.letters = line.letters;
113 			words.add(word);
114 		}
115 
116 		for (final WordCandidate w : words) {
117 			w.regularBoundingBox = LetterCandidate.computeBounds(w.letters);
118 
119 			for (final LetterCandidate letter : w.letters)
120 				letter.word = w;
121 		}
122 
123 		return words;
124 	}
125 
126 	/**
127 	 * Get the letters within this word.
128 	 * 
129 	 * @return the letters.
130 	 */
131 	public List<LetterCandidate> getLetters() {
132 		return letters;
133 	}
134 
135 	/**
136 	 * Get the line containing this word.
137 	 * 
138 	 * @return the enclosing line.
139 	 */
140 	public LineCandidate getLine() {
141 		return line;
142 	}
143 }