Supplementary Material for Our Paper

Multi-Class (Anisotropic) Electrostatic Halftoning

Multi-Class (Anisotropic) Electrostatic Halftoning
Novel Contributions

Our previous halftoning algorithm achieves excellent results, but is has a number of shortcomings: Its visual representation of very dark image regions is unsatisfactory due to overlapping inkblots, and it is only applicable for a single class of dots with a uniform size and colour. The extensions and modifications introduced in our paper show how to overcome these limitations and problems. More specifically, we make the following contributions:

• We introduce the changes necessary to deal with inkblots of different sizes. This also allows to create second order screening results similar to those used in the printing industry. As explained in detail in the paper, our approach contains a tradeoff parameter that can be used to steer the different requirements occurring in such situations. Here, we illustrate the effect of this parameter.
• We give details on how to create halftones for output devices with arbitrary colour models, including asymmetric models such as the CMY-RB-K colour model. Here, we show additional experiments that did not fit into the paper in a high resolution.
• We present our approach to multi-class sampling using different objects with varying sizes. As in the case of multi-size halftoning, we show the effect of the tradeoff parameter we introduced to steer the algorithm.
• Our fourth and last contribution is a novel approach for hatching, which can even be combined with any of the other contributions such that a mixture of dots and lines can be created. Thereby, a user can freely specify the desired lengths and directions of the lines depending on their positions in the image.

Additionally, this page illustrates how to improve visual results in dark image areas. This is done by adjusting the underlying image before halftoning to account for overlapping inkblots. The deviation of the proposed halftoning operator and the resulting table containing the resulting tonemapping operator for 8-bit channels, which were not included in the paper as they did not really fit into its scope, are given on the following pages.

Main Page   Deviation of Tonemapping Operator >

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