TwobyTwo Centering Printer Model ShenGe Wang Digital Imaging

Two-by-Two Centering Printer Model Shen-Ge Wang Digital Imaging Technology Center, Xerox Corporation October 17, 2001

Two-by-Two Centering Printer Model • Printer characterization – Continuous-tone vs. binary printer models – Color mixing models • Two-by-two printer model – 2 x 2 concept – Modeling CMY and CMYK printers – Reduced Measurement • Applications – Printer calibration – Feed-Back for Moire removal

Printer Modeling SCANNER Printer Calibration Lab PRINTER Color Halftoning CMYK 8 PRINTER CMYK 1 Lab

Printer Modeling Printer Calibration Lab • Continuous-Tone Printer Model (Area Based) • Binary Printer Model (Pixel Based) Color Halftoning CMYK 8 PRINTER CMYK 1 Color Halftoning Lab PRINTER CMYK 8 CMYK 1 PRINTER Lab

Dot Overlapping

“Solid” Color

Two-by-Two Centering

Color Mixing • Neugebauer Equation • Yule - Nielsen Modification • B/W 2 x 2: • CMYK 2 x 2: N=7 N = 1, 072 N = 16, 576

Reduced Measurement • Colors of three- and four-colorant 2 x 2 patterns can be derived from one- and two-colorant 2 x 2 patterns – One-colorant: – Two-colorant: • Measurement Reduction (Approach A) – CMY: – CMYK: Complete 2 x 2 1, 072 16, 576 Reduced 228 468

CMY 2 x 2 Decomposition (1) = + +

CMY 2 x 2 Decomposition (2) = + +

CMY 2 x 2 Decomposition (3) = + +

CMY 2 x 2 Decomposition (4) = + = +

Color Mixing: Approach A = + 1. Area Decomposition 2. Color Mixing

CMYK 2 x 2 Calibration Target

Feed-Back Application Printer Calibration Color Halftoning PRINTER Input Output Feed-Back Correction 2 X 2 Printer Model • Color Correction • Moiré Removal • Eliminating Artifacts

Feed-Back Application Uncorrected Output First-Pass Difference Feed-Back Corrected Output Second-Pass Difference

Uncorrected Output

First-Pass Difference

Corrected Output

Second-Pass Difference

Conclusion • 2 x 2 Printer Model – Binary CMYK Input – Macroscopic-Measurement Based • Reduced Measurement – ~ 500 Patches for CMYK Printers • Applications – Halftone Independent Printer Calibration – Overlapping Correction for Color Halftoning – Feedback for Reducing Moiré and other artifacts