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Khmer OCR

LONG SeangmengLecturer and researcher, GIC - ITC

seangmeng@itc.edu.kh

Scientific Day 3th May, 2012

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Khmer OCR

• What is OCR?• Khmer OCR Project• State of the Art• Khmer OCR System• Project status• Perspectives

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Optical Character Recognition (OCR)

OCR

Text Image

Editable Text

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Khmer OCR Project

• 2011• Team– Dr. SENG Sopheap, ITC– Mr. LONG Seangmeng, ITC– Mr. EN Sovann (doing master)– Ms. PRUM Sophea (doing PhD)– Mr. HAO Jeudi (5th year)

• Develop a Khmer OCR system– Font independent– Size independent

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State of the ArtAuthor Limitation Result

CHEY Chanoeurn, KOSIN Chamnongthai and PINIT Kumhom

10 characters (បពជកភណឃសវទ)

92%

CHEY Chanoeurn, KOSIN Chamnongthai and PINIT Kumhom

20 fonts 92.85% (size 22)91.66% (size 18)89.27% (size 12)

ING Leng Ieng and MUAZ Ahmed

Limon R1 22 98.88%

KRUY Vanna Font and size independent(manual preparation for new fonts)

97%

EN Sovann Font and size independent(manual preparation for new fonts)

96%

Khmer OCR System

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Pre processing

Segmentation

Recognition

Post processing

Text Image

Editable Text

សា លា �្ ក �្ ង �្ ភ ្�

សាលាក�ងភ��ពេពញនិ�ងសហជ�ព

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Khmer OCR System (cont.)

• Pre processing Binarization

Noise removal

Skew detection and correction

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Khmer OCR System (cont.)• Segmentation

Line

Vertical Symbol

Blob

Page

Line 1

Line 2

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Khmer OCR System (cont.)• Recognition

Blob

Training images (sample images) with label

…

Blob to be recognized

Search for closest match

Closest match

Image:

Label: ក

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Khmer OCR System (cont.)• Recognition (cont.)

– How to find closest match?– How to represent the blob image?

• Fourier transform: Any function f(t) with period T can be written as

Blob image => 2-D Fourier transformThe blob image (B) represented by Fourier coefficients:

B[0], B[1], B[2], …City block distance between two blobs B and B’:

Distance = |B[0] – B’[0]| + |B[1] – B’[1]| + |B[2] – B’[2]| + …

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Khmer OCR System (cont.)• Post processing ឦ

ញAssembling

Blob

សា លា �្ ក �្ ង �្ ភ ្� ពេ្ ព ញ �្ និ ង

សា លា �្ក �្ ង �្ភ ្� ពេ្ព ញ �្និ ង

សាលា �្ក�ង�ភ�ពញ�និង

សាលាក�ងភ��ពេពញ

Reordering

ក��

ត្�ង ក�ង

ពេបស�

ភ��

របស�

Spell Checking

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Project status• Pre processing

– Binarization and noise removal √– Skew detection and correction X

• Segmentation √• Recognition

– Features extraction √– Automatic generation of training data for new fonts √

• Post processing– Assembling and reordering rules

• Manual √• Automatic X

– Spell checking X• Performance evaluation X

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Perspectives• Joining characters• Text layout• Low quality text images• Curve line

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Thanks for your attention!

Demo & Questions???