Gaining Colour Stability in Live Image Capturing

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Talk given at APIS 2008

Talk given at APIS 2008

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  • 1. Motivation Colour Capturing Colour Management Solution Summary Gaining Colour Stability in Live Image Capturing Guy K. Kloss Computer Science Massey University, Albany International Conference on Applications and Principles of Information Science 29 January 2008 Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 1/30
  • 2. Motivation Colour Capturing Colour Management Solution Summary Outline 1 Motivation 2 Colour Capturing 3 Colour Management 4 Solution Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 2/30
  • 3. Motivation Colour Capturing Colour Management Solution Summary Outline 1 Motivation 2 Colour Capturing 3 Colour Management 4 Solution Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 3/30
  • 4. Motivation Colour Capturing Colour Management Solution Summary The Basic Problem We do not recognise light changes Cameras do! Colour measurements are off! Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 4/30
  • 5. Motivation Colour Capturing Colour Management Solution Summary The Basic Problem We do not recognise light changes Cameras do! Colour measurements are off! Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 4/30
  • 6. Motivation Colour Capturing Colour Management Solution Summary The Basic Problem Anticipated Solution Create a system that is able to adapt to the conditions automatically. Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 9/30
  • 7. Motivation Colour Capturing Colour Management Solution Summary Outline 1 Motivation 2 Colour Capturing 3 Colour Management 4 Solution Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 10/30
  • 8. Motivation Colour Capturing Colour Management Solution Summary (Human) Colour Sensing Reflection Model Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 11/30
  • 9. Motivation Colour Capturing Colour Management Solution Summary (Human) Colour Sensing Spectral Light Composition relative spectral power Light Source D65 F2 400 450 500 550 600 650 700 wavelength λ [nm] Object relative reflectance 400 450 500 550 600 650 700 wavelength λ [nm] Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 12/30
  • 10. Motivation Colour Capturing Colour Management Solution Summary (Human) Colour Sensing Spectral Light Composition S M L relative sensitivity S M L 400 450 500 550 600 650 700 wavelength λ [nm] B G R relative sensitivity 400 450 500 550 600 650 700 wavelength λ [nm] Relative sensitivities of cone cells (spectrum top). Typical camera sensors (spectrum bottom). Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 13/30
  • 11. Motivation Colour Capturing Colour Management Solution Summary Colour Capturing Werner Heisenberg, Physics and Philosophy (1958) “What we observe is not nature itself, but nature exposed to our method of questioning.” Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 14/30
  • 12. Motivation Colour Capturing Colour Management Solution Summary Colour Capturing Capturing Process Sensing Rendering Encoding Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 15/30
  • 13. Motivation Colour Capturing Colour Management Solution Summary Colour Capturing Problems Sensor readings are not passed through, they are “interpreted!” Measurement dependent on . . . Illuminant Surface Colour Camera Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 16/30
  • 14. Motivation Colour Capturing Colour Management Solution Summary Colour Spaces Lost in Colour Space? RGB, sRGB, Adobe RGB, . . . YUV HLS, HSV CMYK YCrCb XYZ CIE LAB, CIE LUV Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 17/30
  • 15. Motivation Colour Capturing Colour Management Solution Summary Colour Spaces Crash-Course in Sensible Colour Spaces RGB != RGB Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 18/30
  • 16. Motivation Colour Capturing Colour Management Solution Summary Colour Spaces Categorisation Dependency Device dependent Device independent Linearity physical (with intensity) physical (for a specific output device) visual (CIE LAB) Number of Channels Here: Building a system based on visible colours (trichromatic colour spaces) Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 19/30
  • 17. Motivation Colour Capturing Colour Management Solution Summary Colour Spaces Categorisation Dependency Device dependent Device independent Linearity physical (with intensity) physical (for a specific output device) visual (CIE LAB) Number of Channels Here: Building a system based on visible colours (trichromatic colour spaces) Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 19/30
  • 18. Motivation Colour Capturing Colour Management Solution Summary Colour Spaces Categorisation Dependency Device dependent Device independent Linearity physical (with intensity) physical (for a specific output device) visual (CIE LAB) Number of Channels Here: Building a system based on visible colours (trichromatic colour spaces) Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 19/30
  • 19. Motivation Colour Capturing Colour Management Solution Summary Colour Spaces CIE LAB 1976, CIE L*a*b* (and L*u*v* ) Linear (visually), Device Independent, Opponent Colour Space Guy K. Kloss — LAB is shown inStability in Live Image Capturing (Only CIE Gaining Colour the diagrams.) 20/30
  • 20. Motivation Colour Capturing Colour Management Solution Summary Outline 1 Motivation 2 Colour Capturing 3 Colour Management 4 Solution Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 21/30
  • 21. Motivation Colour Capturing Colour Management Solution Summary Colour Management (static) Using ICC profiles and CIE colour spaces Independent, linear PCS (usable for visual processing) Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 22/30
  • 22. Motivation Colour Capturing Colour Management Solution Summary Colour Management (static) Using ICC profiles and CIE colour spaces Independent, linear PCS (usable for visual processing) Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 22/30
  • 23. Motivation Colour Capturing Colour Management Solution Summary Colour Management Input Device Calibration Preconditions: Colour characterisation target Reproducible conditions (illumination) A specific camera 1 Capturing of target 2 Comparison of measurement vs. true values 3 Computation of ICC profile (lookup table) Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 23/30
  • 24. Motivation Colour Capturing Colour Management Solution Summary Colour Management Input Device Calibration Preconditions: Colour characterisation target Reproducible conditions (illumination) A specific camera 1 Capturing of target 2 Comparison of measurement vs. true values 3 Computation of ICC profile (lookup table) Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 23/30
  • 25. Motivation Colour Capturing Colour Management Solution Summary Colour Management Input Device Calibration Preconditions: Colour characterisation target Reproducible conditions (illumination) A specific camera 1 Capturing of target 2 Comparison of measurement vs. true values 3 Computation of ICC profile (lookup table) Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 23/30
  • 26. Motivation Colour Capturing Colour Management Solution Summary Colour Management Input Device Calibration Preconditions: Colour characterisation target Reproducible conditions (illumination) A specific camera 1 Capturing of target 2 Comparison of measurement vs. true values 3 Computation of ICC profile (lookup table) Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 23/30
  • 27. Motivation Colour Capturing Colour Management Solution Summary Colour Management Problems for Live Capturing The Problem: This does not work in changing/live environments! Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 24/30
  • 28. Motivation Colour Capturing Colour Management Solution Summary Outline 1 Motivation 2 Colour Capturing 3 Colour Management 4 Solution Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 25/30
  • 29. Motivation Colour Capturing Colour Management Solution Summary Approaches for a Solution Usable Clues: A priori knowledge Infering by image analysis (Colour Constancy methods) Advantage of slow changes: Image segmentation Observe background changes Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 26/30
  • 30. Motivation Colour Capturing Colour Management Solution Summary Approaches for a Solution Usable Clues: A priori knowledge Infering by image analysis (Colour Constancy methods) Advantage of slow changes: Image segmentation Observe background changes Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 26/30
  • 31. Motivation Colour Capturing Colour Management Solution Summary Approaches for a Solution Usable Clues: A priori knowledge Infering by image analysis (Colour Constancy methods) Advantage of slow changes: Image segmentation Observe background changes Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 26/30
  • 32. Motivation Colour Capturing Colour Management Solution Summary Putting it Together De-coupled live process: Processing loop with “pay load” Adaptation process Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 27/30
  • 33. Motivation Colour Capturing Colour Management Solution Summary Summary Overview in Colour Science → Colour Sensing/Measuring, Colour Representation Colour Management → Industry Standards and Best Practices, Static Characterisation Dynamic/Live Solution → Usable Clues, Implementation Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 28/30
  • 34. Motivation Colour Capturing Colour Management Solution Summary Questions? What colour is the lemon? If you look closely, you may be surprised! G.Kloss@massey.ac.nz Guy K. Kloss — Gaining Colour Stability in Live Image Capturing 30/30