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fix failure to OCR: general quality issue due to LSTM being fed noisy/crappy *original* image pixels instead of cleaned-up binarized pixels. #4111

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fix failure to OCR: general quality issue due to LSTM being fed noisy/crappy *original* image pixels instead of cleaned-up binarized pixels. #4111

wants to merge 1 commit into from

Commits on Aug 5, 2023

  1. - fix Bushnell OCR bug (failure to properly OCR the number "11"; see … 

    …message chain in mailing list: https://groups.google.com/g/tesseract-ocr/c/5jrGvsrdqig/m/jvTG6L9zBgAJ): it turns out tesseract erroneously grabs the ORIGINAL image (instead of the THRESHOLDED/BINARIZED one!) to extract the word box (Tesseract::GetRectImage()) which will be fed into the LSTM OCR neural net in order to OCR the detected text area.

  Ergo: this fix SHOULD improve OCR results generally, as this is a generic bug which impacts ALL text bboxes found in a given input page image, which are then being pumped into the LSTM engine to obtain OCR'ed text.

  This fix was verified to work in an otherwise patched/augmented tesseract rig: GerHobbelt/tesseract: commit series bb37cf3, ffc1997, 15d2952, 69416e5, f49826b, d53c1a2, 44f2f84, where I worked on removing the curious BestPix() API, which SEEMINGLY was originally meant for ScrollView-et-al debug display purposes, but is (IMO) an ill-named API for that purpose.

- remove accompanying, now obsolete, comment

- also remove the need for BestPix() API usage in EquationDetect::PrintSpecialBlobsDensity() by invoking the API that delivers what's actually used there: the image height. Here BestPix() usage is also wrong (theoretically) as the sought-after image height is about the actual height of the binarized image data, which represent the cleaned-up-and-ready-for-use OCR sourcing image data.
    @GerHobbelt
    GerHobbelt committed Aug 5, 2023
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