Optimization of Line Segmentation Techniques for Thai Handwritten

Document

Olarik Surinta

Mahasarakham UniversityThailand

Introduction

• In handwritten recognition, the line segmentation is an essential scheme.

• The occurrence of an inaccurately line segmentation will cause errors in the character segmentation.

• Most of line segmentation techniques have been based on horizontal projection profile technique.

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Introduction (cont)

• The texts in most document images are aligned along horizontal lines.

• Projection profile based techniques may be one of the most successful top-down algorithms

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The characteristic of Thai character

Character types CharacterConsonants ก ข ฃ ค ฅ ฆ ง จ ฉ ช ซ ฌ

ญ ฎ ฏ ฐ ฑ ฒ ณ ด ต ถ ท ธน บ ป ผ ฝ พ ฟ ภ ม ย ร ฤล ฦ ว ศ ษ ส ห ฬ อ ฮ

Vowels อั อะ อา อิ อี อึ อื อุ อูเอ โอ ใอ ไอ ๆ อ็ อ์ อํ

Tones อ่ อ้ อ๊ อ๋10/21/2009 SNLP2009 4

The characteristic of Thai character (cont)

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Thai sentence structure

Based on the horizontal projection profile

• The horizontal projection profile is used in dividing the text image into character line.

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The line segmentation techniques in this research

• 1. The horizontal projection technique• 2. The stripe technique• 3. The comparing Thai character technique• 4. The sorting and distinguishing• (all of techniques based on horizontal projection profile)

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1. The horizontal projection profile

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resultHorizontal histogramImage document

2. The stripe technique

• Firstly, the stripe technique divides image into stripe (small column).

• After that, the horizontal projection profile is used to divided the text image into character lines.

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2. The stripe technique (cont)

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The result of strip technique for horizontal projection profile

3. Technique for comparing Thai character

• This technique takes advantage of the differences in size of characters to differentiate Thai characters between consonants and a group of small vowels and tones.

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Comparing between consonant and a group of small vowel and tone

3. Technique for comparing Thai character (cont)

• First step• The groups are divided into two groups (upper

and lower zone). The higher group is then used to define the line from the image document

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3. Technique for comparing Thai character (cont)

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The result of first step of comparison Thai character technique

3. Technique for comparing Thai character (cont)

• Second step• consider the high value of white pixel between

the line markers and choose a new line marker

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3. Technique for comparing Thai character (cont)

• this technique is complex as there are many steps to be proved.

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The result of comparing Thai character technique.

4. The new technique for sorting and distinguishing

• This technique is not complicated and suitable for Thai character.

• Firstly• Use the histogram of horizontal projection profile

to sort the group of black pixels by starting with the minimum to maximum of black pixel.

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4. The new technique for sorting and distinguishing (cont)

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Sorting the group of black pixels.

4. The new technique for sorting and distinguishing (cont)

• Secondly• Find the maximum difference between two

groups of black pixels• The line marker is marked on the middle of the

group of black pixels when the maximum difference value is less than value of the group of black pixels

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4. The new technique for sorting and distinguishing (cont)

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The result of second step of sorting and distinguishing technique.

4. The new technique for sorting and distinguishing (cont)

• Finally• A new line marker is placed in the middle

between every two conjunction line markers

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4. The new technique for sorting and distinguishing

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Click me to play this video.

Experimental result

• Thai image documents were generated from different peoples.

• Data sets contained varieties of writing styles, and limited to only single-column Thai image documents.

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Experimental result (cont)

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Single-Column

Not Single-Column

Experimental result (cont)

• The line marker is used to define the character line.

• The line makers pass through the image document and do not cross the group of black pixels (line segment is completed).

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Experimental result (cont)

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Complete line segmentation

Experimental result (cont)

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incomplete line segmentation

Experimental result (cont)

Number of lines on image documents

percentage T1 T2 T3 T4

4 46 35 92 100

5 32 26 94 99

6 26 15 88 100

7 31 24 91 96

8 21 32 90 97

9 15 11 85 95

10 18 9 88 97

11 23 12 90 94

12 7 11 88 96

Average 24.33 19.44 89.55 97.11

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T1 is Horizontal projection techniqueT2 is Stripe techniqueT3 is Comparing Thai characterT4 is Sorting and distinguishing

Conclusion

• I have presented four techniques for the line segmentation of Thai language– Horizontal projection profile– Stripe– Comparing Thai character– Sorting and distinguishing

• 4 techniques based on horizontal projection profile

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Conclusion (cont)

• The accuracy of the techniques are– The horizontal projection technique 24.33%– The stripe technique

19.44%(suitable for English character and Oriya text)

– The comparing Thai character technique65.25%– The sorting and distinguishing technique97.11%(complex, many steps to be proved)

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Thank you

Question & Answer

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