Yes, old OCR solutions use binarized content but I see this as a legacy limitation. It was probably done to speed up the processing and also, I suppose, because the algorithms used would not benefit from the extra gray details anyway. Old ocr tech was also print oriented so the text was already near binary.
With a neural network there is no extra time cost in processing grayscale or binary text, they are just float values in both cases. Binarization throws away a lot of data, especially with noisy images, complex backgrounds, etc. (ID documents, smartphone pictures, etc.). Binarization may improve OCR performance but I doubt: a CNN should be easily able to learn to binarize the image itself if this can improve the results. The only advantage I see for binarization is that syntetic training data is binary, so you try to match the real input data to the one used for training. Of course you could corrupt this data to make it grayscale. But I would expect a full grayscale training and prediction to give slightly better results, especially for complex cases. I fine tuned my models using grayscale data (real world crops, not synthetic) and, if possible, I'd like to try to disable the binarization step to see if I get an improvement. Maybe there are some parameters controlling this step. Thanks Lorenzo Il giorno gio 31 gen 2019 alle ore 20:42 Zdenko Podobny <[email protected]> ha scritto: > see inline comments. > > st 30. 1. 2019 o 15:17 Lorenzo Bolzani <[email protected]> napísal(a): > >> >> I suppose this means that the image is always binarized, is this correct? >> > Yes > >> >> Is there any way to avoid it? >> > > Why? IMO OCR engines are running on binarized images see e.g. > https://www.abbyy.com/en-eu/ocr-sdk/key-features/image-processing/ > > >> Does this binarization happens by default during training too? >> > > I do not know. I did not have time to play with training in v 4.0 > >> >> I fine tuned a few models using grayscale images. Do you thing the neural >> network received binary black/white pixels or the gray ones? >> >> I do not know. > >> >> Thanks, bye >> >> Lorenzo >> >> Il giorno mer 30 gen 2019 alle ore 13:28 Zdenko Podobny <[email protected]> >> ha scritto: >> >>> try: >>> tesseract image - get.image >>> which calls GetThresholdedImage() >>> <https://github.com/tesseract-ocr/tesseract/blob/12c1abcb6b4ef90cfafe316a3b40753ee5e9b9ef/src/api/baseapi.cpp#L638> >>> >>> >>> Zdenko >>> >>> >>> st 30. 1. 2019 o 11:17 Lorenzo Bolzani <[email protected]> napísal(a): >>> >>>> >>>> Zdenko, are you 100% sure that the image is binarized before being fed >>>> to the neural network? It looks like a big waste of information to me. >>>> >>>> >>>> Il giorno mer 30 gen 2019 alle ore 07:56 Zdenko Podobny < >>>> [email protected]> ha scritto: >>>> >>>>> That is not true: you do not need to transform image to grayscale. Any >>>>> image is at the end binarized (if input image is not binarized) by >>>>> tesseract (Otsu). >>>>> >>>>> BUT: preprocessing image (e.g. custom binarization) will help. See >>>>> https://github.com/tesseract-ocr/tesseract/wiki/ImproveQuality >>>>> >>>>> Zdenko >>>>> >>>>> >>>>> st 30. 1. 2019 o 7:36 <[email protected]> napísal(a): >>>>> >>>>>> Not a solution, but the image needs to be transformed into >>>>>> grayscaleetc, (using Open CV) since OCR works best with grayed images and >>>>>> images which have size of 300 dpi >>>>>> >>>>>> On Tuesday, June 12, 2018 at 12:44:21 PM UTC+5:30, Vidur Malhotra >>>>>> wrote: >>>>>>> >>>>>>> I tried running the tesseract on the attached image. But not getting >>>>>>> the desired output. My sample code: >>>>>>> >>>>>>> >>>>>>> import PIL >>>>>>> from PIL import Image >>>>>>> import pytesseract >>>>>>> >>>>>>> text = pytesseract.image_to_string(Image.open('test3.jpg'), >>>>>>> lang='eng') >>>>>>> print(text) >>>>>>> >>>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "tesseract-ocr" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>> send an email to [email protected]. >>>>>> To post to this group, send email to [email protected]. >>>>>> Visit this group at https://groups.google.com/group/tesseract-ocr. >>>>>> To view this discussion on the web visit >>>>>> https://groups.google.com/d/msgid/tesseract-ocr/43a5a754-4227-43b6-aec1-0261403b2029%40googlegroups.com >>>>>> <https://groups.google.com/d/msgid/tesseract-ocr/43a5a754-4227-43b6-aec1-0261403b2029%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>>> . >>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>> >>>>> -- >>>>> You received this message because you are subscribed to the Google >>>>> Groups "tesseract-ocr" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>> an email to [email protected]. >>>>> To post to this group, send email to [email protected]. >>>>> Visit this group at https://groups.google.com/group/tesseract-ocr. >>>>> To view this discussion on the web visit >>>>> https://groups.google.com/d/msgid/tesseract-ocr/CAJbzG8zsShhi_LsUXkCWoj8uxWxROkTL7G4RpGwzBEVm1EweTA%40mail.gmail.com >>>>> <https://groups.google.com/d/msgid/tesseract-ocr/CAJbzG8zsShhi_LsUXkCWoj8uxWxROkTL7G4RpGwzBEVm1EweTA%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>>> . >>>>> For more options, visit https://groups.google.com/d/optout. >>>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "tesseract-ocr" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To post to this group, send email to [email protected]. >>>> Visit this group at https://groups.google.com/group/tesseract-ocr. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/tesseract-ocr/CAMgOLLxVGXt527-wkSfGegMtOjMU2LT0rz_H%3Dp8kQZ13CCE1ag%40mail.gmail.com >>>> <https://groups.google.com/d/msgid/tesseract-ocr/CAMgOLLxVGXt527-wkSfGegMtOjMU2LT0rz_H%3Dp8kQZ13CCE1ag%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "tesseract-ocr" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To post to this group, send email to [email protected]. >>> Visit this group at https://groups.google.com/group/tesseract-ocr. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/tesseract-ocr/CAJbzG8zse4y474Uz7w0pJEuyDesRgD6fuQu_Y0cMDzGH4Ux7JA%40mail.gmail.com >>> <https://groups.google.com/d/msgid/tesseract-ocr/CAJbzG8zse4y474Uz7w0pJEuyDesRgD6fuQu_Y0cMDzGH4Ux7JA%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "tesseract-ocr" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at https://groups.google.com/group/tesseract-ocr. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/tesseract-ocr/CAMgOLLwkdPEWjteO1%2BJ0M0TVvfcfB9hvEX-3uQUvo_8dnr%2B2kw%40mail.gmail.com >> <https://groups.google.com/d/msgid/tesseract-ocr/CAMgOLLwkdPEWjteO1%2BJ0M0TVvfcfB9hvEX-3uQUvo_8dnr%2B2kw%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> For more options, visit https://groups.google.com/d/optout. >> > -- > You received this message because you are subscribed to the Google Groups > "tesseract-ocr" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/tesseract-ocr. > To view this discussion on the web visit > https://groups.google.com/d/msgid/tesseract-ocr/CAJbzG8zBcMoYnt1WPjJffLVoRXoFZcBDu5QgnQ3gOyJTobi0aw%40mail.gmail.com > <https://groups.google.com/d/msgid/tesseract-ocr/CAJbzG8zBcMoYnt1WPjJffLVoRXoFZcBDu5QgnQ3gOyJTobi0aw%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "tesseract-ocr" group. 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