Limit tesseract character to a-z and number only in my iOS app

Question

I am using tesseract for recognizing character in one of my iOS project. It is now reading all characters including alpha numeric character. But I want to read only character a-z and numbers 0-9. I followed Limit characters tesseract is looking for, but can't figure out how can I implement this in my iOS app.

Can anyone suggest me how can I implement this in my iOS project.

Answer 1

You can specify the white list (allowed characters) using TessBaseAPI.SetVariable prior to extraction

 tesseract->SetVariable("tessedit_char_whitelist", "abcdefghijklmnopqrstuvwxyz012345789");