Tone Dependent Color Error Diffusion Halftoning

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Tone Dependent Color Error Diffusion Halftoning

• Literature Survey Presentation
• Vishal Monga,
• March 5, 2003

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Introduction
Digital Halftoning Applications and Methods

• Examples of reduced grayscale/color resolution
• Laser and inkjet printers
• Facsimile machines
• Low-cost liquid crystal displays
• Halftoning is wordlength reduction for images
• Grayscale 8-bit to 1-bit (binary)
• Color 24-bit RGB to 3-bit (1 bit per color
  plane)
• Halftoning methods
• Screening - pixel-parallel, fast, and simple
• Search based methods Direct Binary Search(DBS)
• Error diffusion - 2D sigma delta modulation
  Anastassiou, 1989

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Grayscale Error Diffusion
Background

• 2- D sigma delta modulation Anastassiou, 1989
• Shape quantization noise into high frequencies
• Linear Gain Model Kite, Evans, Bovik, 1997
• Replace quantizer by scalar gain Ks and additive
  noise image

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Key Paper 1
Direct Binary Search Analoui, Allebach 1992

• Computationally too expensive for real-time
  applns. viz. printing
• Used in screen design
• Serves as a practical upper bound for achievable
  halftone quality

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Tone Dependent Error Diffusion
Key Paper 2

• Train error diffusionweights and
  thresholdmodulationLi Allebach, 2002

Midtone regions
FFT
DBS pattern for graylevel x
Halftone pattern for graylevel x
FFT
Highlights and shadows
FFT
Graylevel patch x
Halftone pattern for graylevel x
FFT
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Key Paper 3
Linear Color Vision Model Monga, Geisler, Evans,
2003

• Pattern-color separable model Poirson Wandell,
  1993
• Forms the basis for Spatial CIELab Zhang
  Wandell, 1996
• Best color transformation spatial filters
  Monga, Geisler, Evans, 2003