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ECE 638: Principles of Digital Color Imaging Systems

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Presentation on theme: "ECE 638: Principles of Digital Color Imaging Systems"— Presentation transcript:

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


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