23. Halfoning_DBS - 2011 - 2. Direct Binary Search (DBS)...

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Advanced Digital Halftoning – 2 October 2011 2.1 2. Direct Binary Search (DBS)
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Advanced Digital Halftoning – 2 October 2011 2.2 Outline • Overview of search-based halftoning methods • DBS framework • DBS behavior • EfFcient implementation for DBS • Dual interpretation for DBS • DBS with embedded printer models – Electrophotographic – Inkjet • Color DBS – Search in YCxCz color space – Search in CMYK color space • Some recent work – Clustered DBS – Modeling larger neighborhood in±uence
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Advanced Digital Halftoning – 2 October 2011 2.3 Overview of Search-Based Methods Search-based methods use numerical optimization strategies to find the best halftone image. These methods are usually iterative. They can be used to design: – Constant gray-value texture patches – LUT texture stacks – Macroscreens – Optimal halftone images Search methods include: – Linear programming – Simulated annealing – Gerchberg-Saxton iteration – Direct binary search (DBS)
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Advanced Digital Halftoning – 2 October 2011 2.4 DBS Framework [Analoui and Allebach, 1992]* + - g 0 [ n ] f[ n ] f( x ) ~ g( x ) ~ ~ e( x ) arg min g[ n ] x ( e( x ) ) 2 d x ~ . . . g[ n ] p( x ) ~ Human visual system filter kernel p( x ) ~ Human visual system filter kernel *Similar algorithms reported at same time by Pappas and Neuhoff and Mulligan
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Advanced Digital Halftoning – 2 October 2011 2.5 The Search Heuristic Toggle Swap 1 Swap 2 Swap 3 Accept pattern with lowest error
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Advanced Digital Halftoning – 2 October 2011 2.6 DBS Convergence: 0, 1, 2, 4, 6, and 8 Iterations
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Advanced Digital Halftoning – 2 October 2011 2.7 Swaps vs. Toggles Toggle only Swap and toggle
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Advanced Digital Halftoning – 2 October 2011 2.8 Device model (linear, shift-invariant) Image rendered on print or display Digital image used to drive printer or display Display/printer spot profile Assumes additive spot overlap Assume identical model for continuous-tone image g ( x , y ) = g [ m , n ] p ( x mX , y nX ) n m g [ m , n ] p ( x , y ) f ( x , y ) = f [ m , n ] p ( x mX , y nX ) n m
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Advanced Digital Halftoning – 2 October 2011 2.9 HVS model and error image
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Advanced Digital Halftoning – 2 October 2011 2.10 Error metric
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Advanced Digital Halftoning – 2 October 2011 2.11 Impact of scale parameter Scale parameter S = RD ; R = resolution in dpi, D = viewing distance in inches. Role in DBS dsdt S n t S m s h t s h D n m c p p ) 180 , 180 ( ) , ( ) ( 180 ] , [ 2 2 ~ ~ π ∫∫ + + = S 1 =0.5S 2 S 3 =2.0S 2 S 2 =300 x 9.5
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2.12 Efficient computation Direct computation of effect of a trial change requires operations for filter containing pixels. Filter Support
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This note was uploaded on 02/19/2012 for the course ECE 638 taught by Professor Staff during the Fall '08 term at Purdue University-West Lafayette.

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23. Halfoning_DBS - 2011 - 2. Direct Binary Search (DBS)...

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