Electrophotographic-model-based halftoning and analysis of clustered-dot halftoning with direct binary search
Abstract
Most halftoning algorithms assume there is no interaction between neighboring dots or if there is, it is additive. Without accounting for dot-gain effect, the printed image will not have the appearance predicted by the halftoning algorithm. Thus, there is need to embed a printer model in the halftoning algorithm which can predict such deviations and develop a halftone accordingly. The direct binary search (DBS) algorithm employs a search heuristic to minimize the mean squared perceptually filtered error between the halftone and continuous-tone original images. We incorporate a measurement-based stochastic model for dot interactions of an electro-photographic printer within the iterative DBS binary halftoning algorithm. The stochastic model developed is based on microscopic absorptance and variance measurements. We present an efficient strategy to estimate the impact of 5×5 neighborhood pixels on the central pixel absorptance. By including the impact of 5×5 neighborhood pixels, the average relative error between the predicted tone and tone observed is reduced from around 23% to 4%. Also, the experimental results show that electro-photography-model based halftoning reduces the mottle and banding artifacts. We also embed our printer model in stochastic clustered-dot halftoning algorithm CLU-DBS. The method CLU-DBS uses different filters in the initialization and update phases, in comparison to the same filters used in both the phases in the conventional DBS method. In this work, we derive a closed form expression for cost metric that is minimized in the CLU-DBS framework. This cost metric analysis not only provides us in-depth understanding of stochastic clustered-dot halftoning but also simplifies and speeds up the screen design algorithm and it also enables us to embed our printer model to generate visually pleasing stochastic clustered-dot textures.
Degree
Ph.D.
Advisors
Allebach, Purdue University.
Subject Area
Electrical engineering
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