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

leaves of the tree which contain only one text line.
For each pair of lines p and q, let a = (x L 1 , y L 1 ) and b = (x R 1 , y R 1 ) be the
coordinates of the axis points of the line at the top and let e = (x L 2 , y L 2 ) and
f = (x R 2 , y R 2 ) be the coordinates of the axis points of the second line. Then
LL = d(a, e) is the Euclidean distance between the two points on the left and
RR = d(b, f) is the Euclidean distance between the two points on the right.
The criterion for selecting a link at each node of the BPT is:
W bpt (p, q) = (1 + min{LL, RR})(1 + W mst (p, q)).
Starting from the root node, at each level the algorithm selects the link with
maximum W bpt and removes that link. The two resulting set of lines are passed
to the child nodes of the node in process.
tel-00912566, version 1 - 2 Dec 2013
6.3 Paragraph features
Now that the BPT is generated and each node of the BPT contains a potential
paragraph, a set of features should be extracted from each paragraph. Features
are as follows:
• Left indentation of the first line. All computations of the indentation are
done in regard to the bounding box of the paragraph in question.
• Right indentation of the first line.
• Indentation ratio of the first line which is the minimum value between left
and right indentations divided by the maximum value between them.
• Difference between left and right indentations of the first line.
• Left indentation of the last line.
• Right indentation of the last line.
• Indentation ratio of the last line.
• Difference between left and right indentations of the last line.
• Average value of left indentations of the text lines in the paragraph excluding
the first and the last line.
• Average value of right indentations of the text lines in the paragraph
excluding the first and the last line.
• Average indentation radio which is computed based on the average left
and right indentations of the text lines in the middle of the paragraph.
• Maximum left indentation of the text lines in the middle of the paragraph.
• Minimum left indentation of the text lines in the middle of the paragraph.
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