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Add simple orientation detection #34

Merged
merged 4 commits into from
Jun 5, 2022
Merged

Add simple orientation detection #34

merged 4 commits into from
Jun 5, 2022

Commits on Jun 5, 2022

  1. Add simple orientation detection 

    Tesseract's has built-in script and orientation detection but it is part of the
classic (pre-LSTM) engine, which has been compiled out to reduce binary size.
Hence this initial implementation use Leptonica's more simplistic orientation
detection, which is based on counting numbers of ascenders and descenders, as
described on pages 12-14 of http://www.leptonica.org/papers/skew-measurement.pdf.
    @robertknight
    robertknight committed Jun 5, 2022
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  2. Display detected image orientation in OCR web demo 

    In adding this I encountered issues where the same rotated image dropped into
Safari, Chrome and Firefox could give different results. I believe this has to
do with how the EXIF rotation information is handled by the various browser APIs
used to load and draw images, but this still needs to be debugged.
    @robertknight
    robertknight committed Jun 5, 2022
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  3. Include confidence in orientation detection result 

    The confidence value is currently 0 if an error occurred or 1 otherwise.
This at least creates a space in the API to include a confidence score
in the result.
    @robertknight
    robertknight committed Jun 5, 2022
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  4. Add notes about the limitations of the current orientation detection … 

    …method
    @robertknight
    robertknight committed Jun 5, 2022
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