Android Tess-Two OCR unmappable character 'fi'

Question

My android app has an OCR functionality using tess-two library. I have this issue in reading the String which contains "fi". After baseApi.getUTF8Text(), a method to get the recognized text by the OCR, the returned String in that "fi" is "fi" <<<- - - Take a very close attention to that string. It is not a 2-charactered String but a single-charactered String. You can reproduce that by copying and pasting. Now, I am thinking it might be an issue of UTF8 encoding or etc which I don't have enough knowledge with. When I tried to do string.replace("fi","fi"), Android Studio builds with erors unmappable character for encoding utf-8. I tried searching in google but it recognize it as a regular "fi" not "fi".

Is there any way I can fix this character?

Answer 1

You can avoid recognizing the fi ligature by blacklisting it before calling baseApi.setImage:

baseApi.setVariable(TessBaseAPI.VAR_CHAR_BLACKLIST, "fi");

To prevent Android Studio from throwing the unmappable character error on your java code, convert your file encoding to UTF-8 by choosing "UTF-8" from the selector near the bottom right corner of the Android Studio window.

Answer 2

Here's what I found, FWIW: the character 'fi' is a ligature (more at: Unicode Character 'LATIN SMALL LIGATURE FI' (U+FB01))

Here's a quick and dirty program to find and replace 'fi' with any other characters:

public class LigatureFI
{

    static char ligature_fi = 0xFB01;

    public static void main(String[] args)
    {
        String sligature_fi = Character.toString(ligature_fi);
        String string = new String("fififififififififififififififi");
        System.out.println(string);
        string = string.replaceAll(sligature_fi, "FI");
        System.out.println(string);
    }

}

If your IDE complains about 'fi' not being in the cp1252 charset, save as UTF8.

HTH.