Optimization of Line Segmentation Techniques for Thai Handwritten Document Olarik Surinta Mahasarakham University Thailand

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. 10/21/2009SNLP20092

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 10/21/2009SNLP20093

The characteristic of Thai character Character typesCharacter Consonants ก ข ฃ ค ฅ ฆ ง จ ฉ ช ซ ฌญ 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 ฮก ข ฃ ค ฅ ฆ ง จ ฉ ช ซ ฌญ 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 อู เอ โอ ใอ ไอ ๆ อ็ อ์ อํ Tones อ่ อ้ อ๊ อ๋ 10/21/2009SNLP20094

The characteristic of Thai character (cont) 10/21/2009SNLP20095 Thai sentence structure

Based on the horizontal projection profile The horizontal projection profile is used in dividing the text image into character line. 10/21/2009SNLP20096

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) 10/21/2009SNLP20097

1. The horizontal projection profile 10/21/2009SNLP20098 result Horizontal histogram Image 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. 10/21/2009SNLP20099

2. The stripe technique (cont) 10/21/2009SNLP 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. 10/21/2009SNLP 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 10/21/2009SNLP200912

3. Technique for comparing Thai character (cont) 10/21/2009SNLP 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 10/21/2009SNLP200914

3. Technique for comparing Thai character (cont) this technique is complex as there are many steps to be proved. 10/21/2009SNLP 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. 10/21/2009SNLP200916

4. The new technique for sorting and distinguishing (cont) 10/21/2009SNLP 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 10/21/2009SNLP200918

4. The new technique for sorting and distinguishing (cont) 10/21/2009SNLP 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 10/21/2009SNLP200920

4. The new technique for sorting and distinguishing 10/21/2009SNLP 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. 10/21/2009SNLP200922

Experimental result (cont) 10/21/2009SNLP  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). 10/21/2009SNLP200924

Experimental result (cont) 10/21/2009SNLP  Complete line segmentation

Experimental result (cont) 10/21/2009SNLP  incomplete line segmentation

Experimental result (cont) Number of lines on image documents percentage T1 T2 T3 T Average /21/2009SNLP T1 is Horizontal projection technique T2 is Stripe technique T3 is Comparing Thai character T4 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 10/21/2009SNLP200928

Conclusion (cont) The accuracy of the techniques are –The horizontal projection technique24.33% –The stripe technique19.44% (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) 10/21/2009SNLP200929

Thank you Question & Answer 10/21/2009SNLP200930