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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