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Ph.D. Course in Digital Halftoning

Ph.D. Course in Digital Halftoning. Examples of Colorimetric Modeling Methods Lars Bergman, Halmstad University. Papers. A Critical Review of Spectral Models Applied to Binary Color Printing The Spectral Modeling of Large Format InkJet Printers. Forward RGB -> CMY(K) Reversed

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Ph.D. Course in Digital Halftoning

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  1. Ph.D. Course in Digital Halftoning Examples of Colorimetric Modeling Methods Lars Bergman, Halmstad University

  2. Papers • A Critical Review of Spectral Models Applied to Binary Color Printing • The Spectral Modeling of Large Format InkJet Printers Digital halftoning - Lars Bergman

  3. Forward • RGB -> CMY(K) Reversed • How much CMY(K) for a given RGB • Predict the spectral output of the printer • Effective dot area Digital halftoning - Lars Bergman

  4. Effective dot area • Mechanical dot gain • Ink cover larger area on paper then intended • Optical dot gain • Light spread in paper (and ink) Digital halftoning - Lars Bergman

  5. Typical machanical dot gain for a desktop inkjet printer Digital halftoning - Lars Bergman

  6. A Critical Review of Spectral Models Applied to Binary Color Printing

  7. Regression based Murray-Davis Neugebauer Yule-Nielsen Yule-Nielsen modified Neugebauer Cellular Neugebauer Yule-Nielsen with spectral depending N-value First principals models (Regressing the Neugebauer Primarys) (Expanded Murray-Davis Model) The Propability model Modeling paper spread function Models Digital halftoning - Lars Bergman

  8. Murray-Davis Digital halftoning - Lars Bergman

  9. effective area Digital halftoning - Lars Bergman

  10. Neugebauer Digital halftoning - Lars Bergman

  11. Digital halftoning - Lars Bergman

  12. Trys to correct for the non linearity in Murray-Davis model Recomended N=1.7 for offset prints Yule-Nielsen Digital halftoning - Lars Bergman

  13. Digital halftoning - Lars Bergman

  14. Combining Yule-Nielsen and Neugebauer Yule-Nielsen is used separate for each color Yule-Nielsen modified Neugebauer Digital halftoning - Lars Bergman

  15. Cellular Neugebauer Digital halftoning - Lars Bergman

  16. Yule-Nielsen with spectral depending N-value Spectral reflectance for primary cyan ramp Digital halftoning - Lars Bergman

  17. The Propability model Light path Probabilities Digital halftoning - Lars Bergman

  18. Digital halftoning - Lars Bergman

  19. Convolution with LP filter Can handle nonuniform screens/dots Computational heavy Modeling paper spread function Digital halftoning - Lars Bergman

  20. Quality meassure Spectral fitness • RMS Spectral error Tristimulus fitness • Humanly correct • ICC profiles • CIE DE Digital halftoning - Lars Bergman

  21. Model performances Digital halftoning - Lars Bergman

  22. The Spectral Modeling of Large Format InkJet Printers

  23. Screening Determing the number of colors (ink combinations) Digital halftoning - Lars Bergman

  24. HP650C HP650 use ”Scatter mode” FM-based screening Digital halftoning - Lars Bergman

  25. Testdata Primary ramp CMYRGBK Ramp Test target used to characterize each color types spectral absorptivity. Digital halftoning - Lars Bergman

  26. Meassured spectral rflectance factor data of a cyan ramp Digital halftoning - Lars Bergman

  27. Linear model prediction for 50% cyan using Murray-Davis model Digital halftoning - Lars Bergman

  28. Normalized reflectance factor spectra for cyan ramp data Digital halftoning - Lars Bergman

  29. Normalized reflectance factor spectra for cyan ramp data using Yule-Nielsen-model N=1.7 Digital halftoning - Lars Bergman

  30. Normalized reflectance factor spectra for cyan ramp data using Yule-Nielsen-model N=10 Digital halftoning - Lars Bergman

  31. Linear model prediction for 50% cyan Digital halftoning - Lars Bergman

  32. Normalized absorbtion spectra for cyan ramp data using Kubelka-Munck transparent model Digital halftoning - Lars Bergman

  33. Normalized absorptivities based on eigenvector analyses of eight possible color types. Digital halftoning - Lars Bergman

  34. Method • Evaluate halftoning algorithm in order to determine the number of possible colortypes. • Hypothesize a color formation model • Evaluate how well the hypothesized model predict primary ramps • Evaluate secondary and tertiaries ramps • Quantify the mechanical dot gain Digital halftoning - Lars Bergman

  35. Experiments • Device driver • GCR • Registration • Test target design • Printer stability Digital halftoning - Lars Bergman

  36. Optimized Yule-Nielsen n value for CMYRGBK Digital halftoning - Lars Bergman

  37. The END

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