I see. I will spend some time learning the structure of tesseract's network
and give it a try.

Thanks for the help!

On Tue, Jan 9, 2018 at 1:17 PM, ShreeDevi Kumar <[email protected]>
wrote:

> Fine-tune plus-minus will work for few character changes.
>
> You want to delete thousands of characters.
>
> Maybe you need replace top layer type of training.
>
>
>
> On 09-Jan-2018 7:32 AM, "Yang Yu" <[email protected]> wrote:
>
>> Thanks for your reply!
>>
>> The #iterations I always used is 2000/3000/5000/10000. Is it reasonable?
>>
>> I also try to extract dawg from HanS.traineddata and convert it to
>> wordlist, and use it to generate base traineddata to fine-tune. I have
>> confirmed that the new model's dawg->wordlist has the words that consist of
>> my limited unicharset, but the problem still exists.
>>
>> To give more background, my scenario is to recognize plate number from
>> vehicle license. The target image is something like "one Chinese character
>> + several English letters or digits" (see one example image below). So the
>> results are by design not some meaningful words. My training data has 5000
>> such plate numbers, one line for each as text. The reason why I want to
>> retrain is the fact that the number of possible Chinese character at
>> position 0 is limited to ~30.
>>
>> Am I doing anything wrong?
>>
>> [image: Inline image 1]
>>
>>
>>
>> On Mon, Jan 8, 2018 at 11:36 PM, ShreeDevi Kumar <[email protected]>
>> wrote:
>>
>>> How many iterations did you use for training?
>>>
>>> You can unpack HanS.traineddata and then run dawg2word program to get
>>> the wordlists used in it. Try using these for langdata in addition to your
>>> training text.
>>>
>>>
>>>
>>>
>>>
>>> ShreeDevi
>>> ____________________________________________________________
>>> भजन - कीर्तन - आरती @ http://bhajans.ramparivar.com
>>>
>>> On Mon, Jan 8, 2018 at 6:30 PM, Yang Yu <[email protected]> wrote:
>>>
>>>> Hi,
>>>>
>>>> These days I was working on fine-tuning a Chinese tesseract model based
>>>> on 4.0 LSTM, and it worked great when the unicharset is not changed. But I
>>>> found a problem when I applied it to a different scenario.
>>>>
>>>> Basically in my new scenario, the target characters are very limited -
>>>> I only need to recognize less than 100 Chinese characters instead of
>>>> thousands. I find this
>>>> <https://github.com/tesseract-ocr/tesseract/wiki/TrainingTesseract-4.00#fine-tuning-for--a-few-characters>
>>>> link about how to use a different set of unicharset to achieve this.
>>>> Concretely, what I did is:
>>>>     1. Prepare some text with only the characters I need
>>>>     2. Run tesstrain.sh to generate images, and unicharset +
>>>> traineddata + lstmf files (here I use chi_sim as langdata dir)
>>>>     3. Run fine tuning: continued from HanS.lstm which is extracted
>>>> from HanS.traineddata, use the generated chi_sim.traineddata as base
>>>> traineddata, and use HanS.traineddata as old_traineddata
>>>>
>>>> The training process is smooth. But when I applied this new model to my
>>>> evaluation set, I found that for some of my test cases, it worked better;
>>>> but for the rest, the model just output empty string. As comparison, if I
>>>> directly use a fine-tuned model based on HanS.traineddata without changing
>>>> the unicharset (say, just adding some new lstmf files to fine tune), EVERY
>>>> test cases can output something (no matter it is correct or not).
>>>>
>>>> Personally I don't think it is related to overfitting, because even a
>>>> bad model should output something wrong. I'm not sure if it is related to
>>>> chi_sim under langdata - it seems that langdata for 4.0 is not released
>>>> yet, so chi_sim is the only thing I can use to fine-tune HanS.trainneddata
>>>> model.
>>>>
>>>> Any help will be appreciated.
>>>>
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