detection of vertical texts (container BIC codes) with tesseract OCR fails

0
votes

I'm trying to use Tesseract Open Source OCR Engine for a text detection of intermodal (shipping) containers codes in BIC format. BTW, I'm using tesseract through pytesseract and I preprocess input photos with few standard opencv filtering (huge rescaling/blurring/denoising/binarization).

I tuned tesseract (version: tesseract 5.0.0-alpha-647-g4a00) in this way:

  config = (
    # only a set of characters
    ' -c tessedit_char_whitelist=0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ' +

    # no language model
    ' -c load_system_dawg=0' +
    ' -c load_freq_dawg=0' +

    ' -c enable_new_segsearch=1' +

    ' -c language_model_penalty_non_freq_dict_word=1' +
    ' -c language_model_penalty_non_dict_word=1' +

    # select segmentation mode
    ' --psm 11'
  )

I got hopeful results when codes are horizontal-aligned, as in this case:

enter image description here

but I have issues with vertical texts, as in the example show in the photo:

enter image description here

In this last case tesseract doesn't produce an useful result. Why tesseract fails event if input image seems "good"? Any suggestion about how to improve engine recognition?

1
ocrtesseractdetectionimage-recognitionpython-tesseract

1 Answers

0
votes

Try running with --psm 5 :

pagesegmode values are:
  5 = Assume a single uniform block of vertically aligned text.