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ECES 682 Digital Image Processing Week 6

ECES 682 Digital Image Processing Week 6. Oleh Tretiak ECE Department Drexel University. Announcements. Midterm has been graded Grades posted on webct Average Select your project! Project due on May 15 Final exam on Monday, June 12. Image Distortion Model.

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ECES 682 Digital Image Processing Week 6

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  1. ECES 682 Digital Image ProcessingWeek 6 Oleh Tretiak ECE Department Drexel University Digtial Image Processing, Spring 2006

  2. Announcements • Midterm has been graded • Grades posted on webct • Average • Select your project! Project due on May 15 • Final exam on Monday, June 12 Digtial Image Processing, Spring 2006

  3. Image Distortion Model • Restoration depends on distortion • Common model: convolve plus noise • Special case: noise alone (no convolution) Digtial Image Processing, Spring 2006

  4. Thoughts on Restoration • Enhancement vs restoration • Enhancement: cosmetic • Restoration: substantive • In reality, there’s a continuum • Restoration relies on prior knowledge • Example of restoration • Inverse filtering • Noise removal • Nonlinear processing Digtial Image Processing, Spring 2006

  5. Chapter 6, Color Image Processing • Color fundamentals and models • Pseudocolor • Slicing • False-color maps • Index color • Multispectral color models • Color transformations • Smoothing and sharpening • Color segmentation Digtial Image Processing, Spring 2006

  6. Retinal Physiology and Color • Human retinas have (at least) four types of photoreceptors • Three types of ‘cones’ • High light level, high acuity vision • Each type of cone has a different spectral response • One type of ‘rods’ • Low-light level and peripheral vision • There is substantive genetic diversity in color receptors • Different spectral response of photoreceptor • Absence of one of the pigments • Many more phenomena... Digtial Image Processing, Spring 2006

  7. Spectral Response of Cones Digtial Image Processing, Spring 2006

  8. Color Matching Theory • Young’s observation • Any uniform color can be matched by projecting three different light sources onto a screen • In the 1920’s, an international effort on the part of a number of physicists let to the CIE standard color theory • The effort attempted to simplify and standardize • There have been many refinements, but the basic theory still stands • Theory useful for matching pigments (all paint stores have spectrophotometers) and design of color media systems Digtial Image Processing, Spring 2006

  9. Tristimulus Values Digtial Image Processing, Spring 2006

  10. Chromaticity Diagram • From http://www.efg2.com/Lab/Graphics/Colors/Chromaticity.htm • White is (1/3, 1/3, 1/3) • Y is the subjectiveintensity. Digtial Image Processing, Spring 2006

  11. Standard Observer Digtial Image Processing, Spring 2006

  12. Better Subjective Color • Constant distances in x, y space do not correspond to ‘constant’ changes of color • A better linear space is provided by the Y-U-V coordinates Digtial Image Processing, Spring 2006

  13. RGB Coordinates • With the advent of color television, the RGB coordinates were introduced to conveniently produce color on a color cinescope (cathode ray tube) Digtial Image Processing, Spring 2006

  14. RGB Gamut • Color space produced by a specific set of phosphors or LCD filters is limited Digtial Image Processing, Spring 2006

  15. Constant-Color-Difference Coordinates • For modulation (analog TV) and encoding (digital TV, JPEG), Y-U-V-like coordinates are produced • R’, G’, B’ are gamma corrected RGB. These are used in electronic media. Digtial Image Processing, Spring 2006

  16. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  17. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  18. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  19. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  20. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  21. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  22. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  23. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  24. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  25. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  26. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  27. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  28. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  29. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  30. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  31. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  32. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  33. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  34. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  35. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  36. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  37. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  38. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  39. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  40. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  41. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  42. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  43. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  44. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  45. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  46. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  47. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  48. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  49. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

  50. Chapter 6 Color Image Processing Digtial Image Processing, Spring 2006

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