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

Figure 2.6: Part of a camera-captured document from [17] that shows skewed text
lines.
tel-00912566, version 1 - 2 Dec 2013
Figure 2.7: Left image is a cropped part of a document from ICDAR2009 database
and Right image is an advertisement page from our own corpus. Both show vertical
text lines that are hard to detect.
historical document; however, they are seldom seen in more recent documents.
• Skewed text lines appear on camera-captured books. Thick books are
often hard and time-consuming to be scanned manually using flat scanners.
One solution is to use an automated system to turn pages and take
photos of each page. The downside is that text lines appear to be skewed
near the borders. Figure 2.6 shows part of a camera-captured document
from [17] containing the mentioned skewed text lines.
• Vertical text lines often exist in magazine-style pages or advertisements.
They come in two flavours. Either characters are in correct direction but
appear on top of each other, or the whole line with all characters is rotated
by ±90 ◦ . Most methods are designed to detect slanted text lines with a
limited degree of freedom; however, over-segmentation errors occur when
the algorithm is not designed to deal with vertical text lines. Figure 2.7
shows an example of these vertical lines that can be found occasionally in
documents.
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