28. Design_of_color_periodic_clustered-dot _creen_sets

28. Design_of_color_periodic_clustered-dot _creen_sets -...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Advanced Topics in Digital Halftoning – 28-30 October 2008 3.3.1 3.3 Screening Part 3
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Advanced Topics in Digital Halftoning – 28-30 October 2008 3.3.2 Synopsis Screening architecture Screen taxonomy Screen descriptors Analysis of tone and detail Stochastic screens Multilevel screens Periodic, clustered-dot screens (hybrid screen) Design of tile vectors for periodic, clustered-dot screens
Background image of page 2
Advanced Topics in Digital Halftoning – 28-30 October 2008 3.3.3 Design of tile vectors for periodic, clustered-dot screens – outline Mathematical preliminaries Design framework Screen vector search Conventional moire-free condition Common periodicity Halftone microtexture spectrum Correlation factor Experimental results Incorporation of media/colorant/light interaction and human visual system model
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Advanced Topics in Digital Halftoning – 28-30 October 2008 3.3.4 Color Halftoning Overall Procedure Example: http://en.wikipedia.org/wiki/Halftone - Separately halftone each color with a different screen of an unique angle - Typically, use set of 75, 15, 0, and 45 for C,M,Y, and K - Four halftone textures are superimposed - Moiré patterns appear in the final halftone
Background image of page 4
Advanced Topics in Digital Halftoning – 28-30 October 2008 3.3.5 Rosette Ref: “Analysis of the microstructures ‘rosettes’ in the superposition of periodic layers,” by Issac Amidror ± The interaction between periodic patterns can generate new structures which was not in the original: 1) macrostructures (moiré patterns) and 2) microstructures (rosette pattern) ~ line angle ± ~ line period ± Another example: visible moiré patterns Rosette pattern
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Advanced Topics in Digital Halftoning – 28-30 October 2008 3.3.6 Objectives Motivation For digital printers, designing the exact set of 75, 15, 0, and 45 is not feasible due to the lower resolution of dots compared to analog screens But, there is still a lot of freedom to choose different screen sets for a given printer Slight registration errors can lead to color shifts Objective Replace the previous trial and error method Provide a systematic approach to searching for the optimal screen set Reduce visible moiré as much as possible Increase robustness to mis-registration
Background image of page 6
Advanced Topics in Digital Halftoning – 28-30 October 2008 3.3.7 Screen Vectors and Fundamental Frequencies Tile vectors Frequency Components Periodic Clustered- Dot ~ tile vectors ~ periodicity matrix ± ~ fundamental frequencies ± ~ frequency matrix ± Periodicity matrix Frequency matrix ± dots-per-inch
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Advanced Topics in Digital Halftoning – 28-30 October 2008 3.3.8 Overall Procedure ~ a set of screen sets which satisfy the search constraints ~ a set of screen sets which pass the conventional moiré-free conditions ~ a set of screen sets which pass the new moiré-free conditions ~ the optimal screen set ~ the threshold frequency set at somewhere between 50 ~ 70 lpi
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 61

28. Design_of_color_periodic_clustered-dot _creen_sets -...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online