There aren't many articles when we search on the Internet about KhmerOCR topic, I, myself don't find a lot as well.
Of course, I believe that there are some people or companies might quietly in implementing the solution for that but without any announce I believe my presume below are relevant enough for people to understand about current situation of Khmer OCR.
Let's share around "State of The Art Of KhmerOCR" today ;)
I could find that, there are about several Khmer OCR researches being published through some organization, website and universities.
Methodologies
When we talk about Khmer OCR, we suppose around the solutions to make any characters from scanned images of handwritten, typewritten or printed text converts into machine-encoded text.
Solutions on OCR system, mostly focus on:
- Pre-processing (usually is noise removal)
- Segmentation
- Line segmentation
- Character segmentation
- Recognition
- Mapping (Character Assembling)
And there are some methods already used for Khmer OCR in
segmentation or recognition part such as
- Lagendre Moment Descriptor,
- Wavelet Descriptor,
- Hidden Markov model (HMM),
- Back propagation,
- Scale Invariant Fourier Transform (SIFT),
- Fourier Descriptor, Hole detection
- Template Matching
- etc.
- And (it seems) the last one is: Support Vector Machine (SVM)
Literature Review/History
I might miss some others but here are what I could find about what have done so far with this topic.
If you, guys, have know some more, please share to people through comment form. I will check and update.
- The Khmer Printed Characters Recognition using Lagendre Moment
Descriptor by Chey Chanoeurn et al got 92% of accuracy on 10 Khmer
consonants including ប ព ជ ក ភ ណ ឃ ស វ and ឆ
- 2005, The Khmer Printed Character Recognition Using Wavelet
Descriptors by Chey Chanoeurn et al got the accuracy of 92.85%,
91.66% and 89.27% on 10 types of Khmer fonts in 3 different sizes.
- 2008, The Khmer Segmentation for font Limon S1, size 22 by Ing Leng
Ieng, PAN Localization Project got the accuracy of 99.11%.
- 2009, The Khmer OCR for Limon R1 Size 22 by Ing Leng Ieng from PAN
Localization Project using framing and Discrete Cosine Transform
calculation for recognition based on Hidden Markov Model and got
the accuracy of 98.88%.
- 2011, The Khmer Optical Character Recognition (OCR) by Mr. Kruy Vanna
using Fourier Descriptors, Component’s Holes, and Component’s
Location got accuracy of 97.9% on 19 types of Khmer font.
- 2012, The Khmer Printed Character Recognition uses combining of Edge
Detection and Template Matching by Iech Setha et al for one font
“Khmer OS Content” with font size of 36pt got accuracy of 99%
- 2013, The Khmer Printed Character Recognition using Support Vector
Machine (SVM) based, by Pongsametrey SOK for one font “Khmer OS
Content” with font size of 36pt got accuracy of 98.54% (32pt =
98.62%, 28pt = 98.18%) with training set of font size: 32pt
The research No. 7, I did it and it's submitted at Royal University of Phnom Penh (RUPP). So it's not publicly publish any where yet.
Who are doing it nowadays
That's who I have known around in Cambodia only, it might be people who does some study abroad is also doing it. Anyway here what I have known:
- Institute of Technology of Cambodia (ITC), It seems, there're some
continuing implementation of KhmerOCR there
- Royal University of Phnom Penh (RUPP) also doing some more researches on this matter through students' researches, thesis and with their lecturers.
- Open Institute (Open Forum, KhmerOS.info), I believe that this topic is still interesting by this NGO
- And there are some other individuals as well as I heard (?)
What's Interesting
One opensource OCR engine,
Tesseract OCR, it's a completed engine from the image processing to recognition and its output.
What we need for our Khmer language works for it, we need to analyze "how to train" our dataset.
I also did some training for Khmer as well for Tesseract for some letters, it seems that the system is good to go but there are some thing we need to aware before as I posted a question
here.
I will try to write a post on how to train some characters that I did before.
 |
| Few Training Char, All Are Error |
Why Tesseract at this time?
Previous researches are mostly using their own combination of methods
to solve various issue for Khmer language such as in segmentation or recognition but the pre-processing process (image processing) is also important for a real OCR system and its accuracy.
And I could see that
Tesseract OCR is ready for all of that.
Is There Anyone Already Try for Tesseract?
Yes, you can search on
Google, it has already been trying since 2009 per my search on Google and around.
And it might be already made by some universities or lecturers but remaining unclear for me.
So, Is There Any Ready Tesseract OCR for Khmer?
My presumed answer:
No, I've never heard that there's a ready training set for Khmer yet to use in Tesseract OCR Engine.
But, just today, I checked again at the repo of
Tesseract (14 January 2014), I saw some Khmer config is added (Files: Khmer.unicharset, Khmer.xheights), we need to test if they are working.
Therefore, Students, Lecturers, some NGO or community should take part to help this.
Conclusions
The OCR system is very interesting for people nowadays.
We are using Khmer Unicode since it established in 2003 in the Kingdom and with Unicode, we have Google translate recently. Then, Khmer OCR should be also solved somehow as well.
We need more people to do it, to help, to share and publish.
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Article Revision
- 23/04/2014: Initial the article
Remark:
- If any mistake in above research, please alert me in comment.
- More detail of each research, please find the published paper to read in detail
