Segmentation of heterogeneous document images : an ... - Tel

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tel-00912566, version 1 - 2 Dec 2013 Figure 5.4: Text and gap regions after applying Viterbi algorithm and the resulting text line separators in red. 94
• The fifth step is to remove extended separators that have cut through more than one connected component. When two text lines are located close to each other and contain touching components, a separator might not be available at that particular location. The lack of this separator should be compensated by extending separators in the adjacent zones to pass over the touching characters and separate the two text lines. However, from time to time a separator may be found that incorrectly cuts all the way through a misaligned text line. These extended separators often cut more than one connected components and should be removed. If left untreated, they will cut a single text line into two separate text lines by passing through the middle of the characters. tel-00912566, version 1 - 2 Dec 2013 • The final step is to group connected components into text lines. This can be done by generating an image map that only contains text line separators and contours of the text regions, computed in the previous chapter. A labeling strategy is performed on this map to assign a region id to the pixels of each isolated region. Next, connected components of the page should be analyzed. If a component belongs to two regions it should be assigned to the region that includes the greater part of the component, however if the two regions have roughly equal amount of the component, as it happens in the case of touching text lines, then that component should be divided into smaller pieces and each region takes its own piece. Figure 5.5 displays some steps mentioned above for two document images, illustrating how we get from text line separators to text lines. 5.4 Results It is important to analyze the results of text line segmentation and know where the errors come from. Unfortunately none of the methods are comparable. For example Papavassiliou [75] has applied his method on ICDAR07 handwritten segmentation contest [39], but the dataset used in the competition contains simple double-spaced handwritten documents. These documents do not contain any side notes or multi-column text regions. So applying our method to this dataset, yields the same results as the method developed by Papavassiliou. However, we apply our method on two datasets; the dataset for ICDAR2009 Page Segmentation Competition and the dataset for ICDAR2011 Historical Document Layout Competition [4]. The first dataset contains 60 document pages which reflect commonly occurring everyday documents that are likely to be scanned including pages from magazines and technical journals. The second dataset contains 100 historical documents from most national and major libraries in Europe that are very similar to our own corpus. This dataset consists of handwritten and printed documents of various types, such as books, newspapers, journals and legal documents. The 100 documents for the competition are selected as a representative of different document types with aging artifices, 95
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Resumé La segmentation de page est
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Acknowledgements This work would no
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4.3.2 Text components . . . . . . .
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3.6 Two documents that have obtaine
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6.1 PARAGRAPH DETECTION SUCCESS RAT
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detection and we conclude that the
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Figure 1.8: A screen shot that show
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Chapter 2 Related work tel-00912566
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them. In such circumstances, it wou
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[21] is another texture-based metho
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Figure 2.4: Part of a document in o
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• Degraded quality due to ageing
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2.3.2 Handwritten text line detecti
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(a) Divided strips and their projec
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(a) Five zones 1-5 (b) Projection p
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would be difficult to draw a conclu
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The proposed methods by Xiao [102],
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is assigning a label to a region of
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fixed range. When the elongation ap
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Page 57 and 58: 3. Repeat for m = 1, 2, ..., M •
Page 61 and 62: Chapter 4 Region detection tel-0091
Page 63 and 64: The next advantage of using CRFs is
Page 65 and 66: weights that are assigned to edge a
Page 67 and 68: { 1 if ys = text and y f 1 (y s , y
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Page 75 and 76: f = [y c = 0] × [y tl = 0] f = [y
Page 77 and 78: (a) Ground-truth (b) y c = 0 tel-00
Page 79 and 80: ∂l λ = ∑ ( ∑y∈Y f k (y s ,
Page 81 and 82: incorrect [100]. Several sufficient
Page 91 and 92: Table 4.3: TION COUNT WEIGHTED SUCC
Page 97 and 98: Chapter 5 Text line detection tel-0
Page 103: Having specified the model, a verti
Page 109 and 110: text lines can be divided into two
Page 111 and 112: the two children. The root node rep
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Page 121 and 122: currently working on some of these
Page 123 and 124: • fn (false negative) is the numb
Page 125 and 126: 2 ∗ RA ∗ DR F − Measure = RA
Page 127 and 128: • ”-tn”: This option uses the
Page 129 and 130: [12] T. M. Breuel. Two geometric al
Page 131 and 132: [39] B. Gatos, A. Antonacopoulos, a
Page 133 and 134: [64] K. P. Murphy, Y. Weiss, and M.
Page 135 and 136: [91] M. Stamp. A revealing introduc
Page 137 and 138: Index tel-00912566, version 1 - 2 D
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