Peter Kronenberg created TIKA-3286:
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Summary: Tika not issue an error when language file doesn't exist;
not supporting script files
Key: TIKA-3286
URL: https://issues.apache.org/jira/browse/TIKA-3286
Project: Tika
Issue Type: Improvement
Reporter: Peter Kronenberg
Attachments: list-lang.png
Tika uses a regular expression to validate the language string, assuming it is
set of ISO-639-2 language code separated by plus signs. However, Script files
(in the _script_ directory) can have any arbitrary name, with the only rule
being that the start with a capital letter. The scripts were introduced in
4.0.0, [https://github.com/manisandro/gImageReader/issues/323]
In addition, if the user specifies an invalid language (i.e., the string
matches the regular expression, but there is no corresponding language file in
Tessdata, no error message is issued. Tesseract issues some very ugly and
misleading messages which simply assume that you haven't set the _tessdata_
directory correctly, but they are not captured by Tika (and not sure they would
be appropriate anyway). Tika just blindly calls Tesseract but then doesn't get
any output back.
!image-2021-01-28-13-52-14-978.png!
I suggest parsing the language string by the plus sign and not doing any other
validating on the string, but instead, actually checking to see that the file
exists in either _tessdata_ or _tessdata/script_.
If any of them don’t exists, then throw an exception, similar to what is done
now when the language doesn't match the regular expression.
I've started to prototype this.
Later: I'm trying to clarify how the scripts are intended to be used. The page
referenced above as well as
[https://github.com/tesseract-ocr/tesseract/blob/master/doc/tesseract.1.asc#LANGUAGES
|https://github.com/tesseract-ocr/tesseract/blob/master/doc/tesseract.1.asc#LANGUAGES]imply
that the _-l_ option accepts the name of a language or script. I assumed it
would look in _tessdata_ first and if not found, would look in
_tessdata/script_. But it seems you have to enter the path.
!image-2021-01-28-13-52-56-294.png!
_tesseract --list-lang_s displays them this way
so it clearly knows about the _script_ directory. But it expects the user to
know it as well. Not sure if we want to make Tika work more friendly
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