1. ECE 638: Principles of Digital Color Imaging Systems
Jan P. Allebach
School of Electrical and Computer Engineering

2. What is a digital color imaging system?

3. What else besides printers?
Digital cameras
Flatbed scanners
Mobile phones
Flat panel displays

4. How do we organize all this?
Image capture devices
Interconnection space and processing
Image output devices
Cameras
Scanners
Smart phones
Tablets
Personal computers
Cloud
Displays
Printers

5. What do we need to study in order to understand digital color imaging systems?
Color science
Image capture
Image display
Image printing
Image processing
Image quality models and assessment

6. Color science topics What is color?
Trichromatic model for human vision
Opponent channel models for human vision
Standard color spaces
Models for color imaging devices
Device gamma
Color imaging systems calibration
Transformation between color spaces
White point
Color space interpolation
Gamut mapping
Color appearance models
Color management practices

7. Image capture topics Sensors Scanners
Technologies
Characteristics and models
Scanners
Architecture
Illuminations
Scan bar motion
Spatial analysis of scanning and sampling
Calibration of image capture devices
Descreening
Page classification

8. Image display topics Display technologies
Cathode ray tube
Liquid crystal
Plasma panel
E-paper
Calibration of image display devices
Spatial analysis of image display
Color image quantization

9. Image printing topics Printing technologies
Silver halide-based systems
Ink-based systems
Plate-based systems
Inkjet systems
Toner-based systems
Dry electrophotography
Wet electrophotography
Colorant-media-light interaction
Color trapping
Digital halftoning
Calibration of printing systems

10. Image quality models and assessment topics
Image quality terminology
Basic psychophysical methods
Image artifact assessment
Image quality metrics
Image quality rulers

11. What is color?

12. Let’s see what Microsoft has to say about color

13. Click on “More Font Colors…”

14. HSV

15. HSL

16. Crayon Picker

17. CMYK Picker

18. What did we learn? Lots of different ways to talk about color
Ordering and naming systems
Crayon picker
Coordinate systems
HSV
HLS
CMYK

19. Many questions remain…
How were these attributes chosen?
Hue
Saturation
Lightness
Value
Which CMYK are we talking about?
Rendering device
Capture device

20. CMYK
Cyan (C)
Magenta (M)
Yellow (Y)
Black (K)

21. Which CMYK? – effect of rendering device
HP DJ 970Cse
Mac Driver
HP DJ 970Cse
IPP Driver
Monitor

22. Which CMYK? – effect of capture device
Olympus C3000
Digital Camera
Heidelberg Scanner

23. Different color representations
Are they all equivalent?
How do we get from one to the other?
Can we get from one to the other?
Even if we can, what do all these numbers mean?

24. Example: capture to capture
Given RGB values from one capture device, can we predict RGB values for a second capture device?
Olympus C3000
Digital Camera
Scanner
RGB values
(23, 136, 180)
(203, 11, 52)
(219, 186, 33)
(7, 7, 7)
RGB values
(?, ?, ?)
(?, ?,?)

25. Discussion topic
What is the basis for the equations that underlie color transformations?

26. So what is color?
Color is a sensation experienced by a human being in response to a visual stimulus.

27. What are the key parts of this definition?
Color is a sensation experienced by a human being in response to a visual stimulus.

28. Sensation – human being
Need to understand something about the human visual system
physiology
perception
psychophysics
Relevant courses
EE 595T Psychophysics (Profs. Hong Tan and Zygmunt Pizlo)
PSY606V Vision Seminar (Prof. Zygmunt Pizlo)

29. Visual stimulus Illuminant Viewer Object
Need to understand interaction of illuminant and object
Illuminant
Viewer
Object

30. Why should we care about color?
Important aspect of everyday experience
New imaging and information technologies provide unprecedented ability to manipulate and use color
Capture devices
digital cameras
scanners
Output devices
CRT and LCD displays
Inkjet and laser printers
Intermediaries
PCs, smartphones, tablets
applications
internet and cloud

31. Why should we care…
Color provides valuable information about the world around us
Application areas
manufacturing
medicine
agriculture
environmental
Contexts
image analysis for inspection
machine vision for robotics, unmanned aerial vehicles, driverless cars, etc.
remote sensing