BL Demo Day - July2011 - (3) Image Enhancement for OCR


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Slides from Niall Anderson's 1st presentation on Image Enhancement and OCR at the British Library Demo-day on the 12th July 2011.

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  • While generally used in the pre-processing stage of OCR production, Image Enhancement techniques can, in theory, be used on any digital image, created for whatever purpose. Legacy images – not created with OCR in mind – can also benefit from this approach.
  • Created by IMPACT partner agency NCSR “Demokritos” in Athens
  • Done automatically based on projection profiles and zonal analysis. Can also be resized manually as in this example.
  • Extension of process used in border removal. Can also be resized manually.
  • If automated processing works, why manual intervention? Use in collection triage: finding the best parameters before submitting images to OCR.
  • Items are selected and deselected by clicking on the icons. The workflow parts can also be swapped around for best results
  • BL Demo Day - July2011 - (3) Image Enhancement for OCR

    1. 1. Image Enhancement and OCR Niall Anderson, The British Library, 12 July 2010
    2. 2. What is Image Enhancement? <ul><li>Image enhancement is a suite of technical solutions to improve display or delivery of digital images – particularly text-based images </li></ul><ul><li>Main areas of improvement </li></ul><ul><ul><li>Removing noise and other digital artefacts </li></ul></ul><ul><ul><li>Geometric correction for skewed images </li></ul></ul><ul><ul><li>Geometric correction for warped pages in paper original </li></ul></ul>
    3. 3. Example of an enhanced image Warped Dewarped
    4. 4. Why Image Enhancement? <ul><ul><li>To increase quality of image for display </li></ul></ul><ul><ul><li>To increase quality of image for printing (especially for Print On Demand) </li></ul></ul><ul><ul><li>To increase quality of Optical Character Recognition results </li></ul></ul>
    5. 5. OCR and Image Enhancement <ul><ul><li>OCR will produce its best results on material with the following characteristics </li></ul></ul><ul><ul><ul><li>The layout of the text is simple, with no tables or illustrations; </li></ul></ul></ul><ul><ul><ul><li>The text itself is in a modern, computer-generated typeface; </li></ul></ul></ul><ul><ul><ul><li>The digital image preserves a high contrast between the text block and non-text detail (including blank space) </li></ul></ul></ul><ul><ul><ul><li>The image has been created from a perfectly flat and straight scan (if a digital copy from an analogue source) </li></ul></ul></ul><ul><ul><ul><li>The text of the analogue source is clear, well aligned and consistently presented </li></ul></ul></ul><ul><ul><ul><li>The basic material of the analogue source is undamaged; the text is in a single language </li></ul></ul></ul><ul><ul><ul><li>The image has been taken from the original physical source and not a degraded surrogate (such as microfilm) </li></ul></ul></ul>
    6. 6. IMPACT Image Enhancement toolkit
    7. 7. Types of image enhancement in toolkit <ul><li>Binarisation </li></ul>
    8. 8. Types of image enhancement in toolkit <ul><li>Border removal </li></ul>
    9. 9. Types of image enhancement in toolkit <ul><li>Page splitting </li></ul>
    10. 10. Types of Image Enhancement in toolkit <ul><li>Dewarping </li></ul>
    11. 11. Using the IMPACT Image Enhancement toolkit - 1 <ul><ul><li>Select the directory with your images or copy your images to directory </li></ul></ul>
    12. 12. Using the IMPACT Image Enhancement toolkit - 2 <ul><ul><li>Select the directory for saving the results </li></ul></ul>
    13. 13. Using the IMPACT Image Enhancement toolkit - 3 <ul><ul><li>Select one or more document images </li></ul></ul>
    14. 14. Using the IMPACT Image Enhancement toolkit - 4 <ul><ul><li>Define a processing workflow </li></ul></ul>
    15. 15. Using the IMPACT Image Enhancement toolkit - 5 <ul><ul><li>Select the method for every processing module </li></ul></ul>
    16. 16. Using the IMPACT Image Enhancement toolkit - 6 <ul><li>Execute workflow by pressing &quot;Apply Processes&quot; </li></ul>
    17. 17. Using the IMPACT Image Enhancement toolkit - 7 <ul><ul><li>View results on the preview window or right click on any module at the workflow line and select &quot;View Result&quot;. </li></ul></ul>
    18. 18. Indicative results – Border Removal 22383 images to test border removal BL: 7% BNE: 34% BNF: 34% BSB: 11% JSI: 6% NLB: 2% ONB: 6% Only images with borders 38718 images to test border removal BL: 9% BNE: 29% BNF: 32% BSB: 12% JSI: 11% NLB: 2% ONB: 5%
    19. 19. Indicative results – Page splitting 458 images from BNF to test page split 3009 images to test page split BL: 72% BSB: 10% JSI: 18%
    20. 20. Indicative results - Dewarping IMPACT Page Curl Correction v.4 87.78% (81.98% only coarse correction) BookRestorer 80.87%
    21. 21. Research and references <ul><ul><li>N. Stamatopoulos, B. Gatos, I. Pratikakis and S.J. Perantonis, Goal-oriented Rectification of Camera-Based Document Images , IEEE Transactions on Image Processing, vol. 20, no. 4, pp. 910-920, 2011. </li></ul></ul><ul><ul><li>N. Stamatopoulos, B. Gatos, T. Georgiou, Page frame detection for double page document images , 9th IAPR International Workshop on Document Analysis Systems (DAS 2010), pp. 401-408, Cambridge, MA, USA, June 2010 </li></ul></ul><ul><ul><li>B. Gatos, I. Pratikakis and S. J. Perantonis, Adaptive Degraded Document Image Binarization , Pattern Recognition, Vol. 39, pp. 317-327, 2006 </li></ul></ul>
    22. 22. <ul><li>Questions? </li></ul>
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