How to make tesseract to recognize only numbers, when they are mixed with letters?

I want to use tesseract to recognize only numbers. The problem is that I have mixture of numbers & letters and when I use SetVariable("tessedit_char_whitelist", "0123456789")
for every symbol tesseract returns wrong digit.

Can I set a threshold value so that tesseract omits the symbols with low resemblance?

NOTE: I set tesseract to recognize only digits so there is no confusion between O and 0.

Solution 1:

Recognizing only numbers is actually answered on the tesseract FAQ page. See that page for more info, but if you have the version 3 package, the config files are already set up. You just specify on the commandline:

tesseract image.tif outputbase nobatch digits

As for the threshold value, I'm not sure which you mean. If your input is an unusual font, perhaps you might retrain with a sample of your input. An alternative is to change tesseract's pruning threshold. Both options are also mentioned in the FAQ.

Solution 2:

For tesseract 3, the command is simpler tesseract imagename outputbase digits according to the FAQ. But it doesn't work for me very well.

I turn to try different psm options and find -psm 6 works best for my case.

man tesseract for details.

Solution 3:

For tesseract 3, i try to create config file according FAQ.

BEFORE calling an Init function or put this in a text file called tessdata/configs/digits:

tessedit_char_whitelist 0123456789                 

then, it works by using the command: tesseract imagename outputbase digits

Solution 4:

If one want to match 0-9

tesseract myimage.png stdout -c tessedit_char_whitelist=0123456789

Or if one almost wants to match 0-9, but with one or more different characters

tesseract myimage.png stdout -c tessedit_char_whitelist=01234ABCDE