Many 'question mark' chars in recognized text

[Salvo Piazza]

Hi all,

I've written a little simple program to extract text from image with tesseract 3.0.2 as:

Tesseract instance = Tesseract.getInstance();

instance.setDatapath(currentDir);

instance.setLanguage("ita");

String returner = instance.doOCR(new File(filename));

It works fine but I've many question mark chars '?' in the extracted text.

For example the word fluidi is recognized as ?uidi and much more example...

Does anyone know some tips in order to fix this behaviour?

Thanks in advance,

Salvo.

[zdenko podobny]

fl is recognizes as ligature in English, so there could be the same issue in Italian. If it is replaced with '?' I would guess you have problem with unicode... Can you check it with tesseract executable?

Zdenko

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[Greg Dunkel]

Many OCR programs have trouble with ligatures.

[Salvo Piazza]

Hi Zdenko,

thanks for your response.

I know tesseract at very beginning level, so can you tell me how can I check it? (I use a Linux version of tesseract...)

Thanks,

Salvo.

[Rick Leir]

On Linux try YAGF, it is a GUI front end for Tesseract.  As zdenop said, you have a unicode problem.  You need to use UTF8 for strings.

[zdenko podobny]

OCR a test image with you app, store result to text file. Than OCR the same image with tesseract executable (output should be in text file by default) and compare results.

If output from tesseract executable is OK, but from your app is wrong (e.g. there are only ascii letters) => you have problem within you app (e.g. it does not handle unicode string correctly).

Zdenko

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[Quan Nguyen]

I suspect you have saved the Unicode text output with a wrong character encoding. Try UTF-8 encoding when you save the file. Tesseract may misrecognize the characters but rarely put question marks in their places.