Multilevel screen design using direct binary search
ABSTRACT Screening is an efficient halftoning algorithm that is easy to implement. With multilevel devices, there is a potential to improve the overall image quality by using multilevel screening, which allows us to choose among multiple native tones at each addressable pixel. We propose a methodology for multilevel screen design using direct binary search (DBS). We refer to one period of the screen as a multitone cell. We define a multitone schedule, which for each absorptance level specifies the fraction of each native tone used in the multitone cell. Traditional multitoning uses only one native tone in smooth areas corresponding to absorptance values near the native tones, an approach that introduces contouring artifacts. To reduce contouring, we employ schedules that use more than one native tone at each absorptance level. On the basis of the multitone schedule, multitone patterns are designed level by level by adding native tones under the stacking constraint. At each level the spatial arrangement of the native tones is determined by a modified DBS search. We explore several different multitone schedules that illustrate the image-quality trade-offs in multitone screen design.
- SourceAvailable from: Kartheek Chandu
- "Few methods  are also proposed to reduce these artifacts in multibit screens. A detailed literature review can be found in . In addition, these algorithms require many parameters to guide through the multi-bit screen creation. "
Conference Paper: DIRECT MULTI-BIT SEARCH (DMS) SCREEN ALGORITHM[Show abstract] [Hide abstract]
ABSTRACT: Multi-bit screening is an extension of binary screening, in which every pixel in continuous-tone image can be rendered to one among multiple absorptance levels. Many multi-bit screen algorithms face the problem of contouring artifacts due to sudden changes in the majority absorptance level between gray levels. In this paper, we have extended the direct binary search to the multi-bit case where at every pixel the algorithm chooses the best drop absorptance level to create a visually pleasing halftone pattern without any user defined guidance. This is repeated throughout the entire range of gray levels to create a high quality multi-bit screen.IEEE International Conference on Image Processing (ICIP); 10/2012
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- "To overcome this problem, Yu et al  introduce overmodulation implemented via a lookup-table-based approach. Lin and Allebach  use a schedule-based framework to control the number of native tones used to render any specific graylevel. Bacca Rodriguez et al  implement stochastic, dispersed-dot multilevel halftoning by applying error diffusion to separate channels of the image that has been decomposed according to the range of gray levels. "
ABSTRACT: Multilevel halftoning algorithms are becoming increasingly important as the capabilities of image output devices improve. The traditional approach to multilevel halftoning is hampered by the appearance of contouring in the vicinity of native tones of the output device. To overcome this limitation, we propose a novel framework based on maintaining a consistent periodic, clustered-dot halftone texture across the tone scale. We develop metrics for granularity and structure dissimilarity, and show how these can be used to guide the manner in which the halftone texture evolves from native tone to native tone, across the tone scale. Experimental results confirm the benefits of our new approach.Image Processing (ICIP), 2012 19th IEEE International Conference on; 01/2012
Article: Halftoning Over a Hexagonal Grid[Show abstract] [Hide abstract]
ABSTRACT: In this contribution, we present an optimal halftoning algorithm that uniformly distributes pixels over a hexagonal grid. This method is based on a slightly modified error-diffusion approach presented at SIGGRAPH 2001.1 Our algorithm's parameters are optimized using a simplex downhill search method together with a blue noise based cost function. We thus present a mathematical basis needed to perform spectral and spatial calculations on a hexagonal grid. The proposed algorithm can be used in a wide variety of printing and visualization tasks. We introduce an application where our errordiffusion technique can be directly used to produce clustered screen cells.Proceedings of SPIE - The International Society for Optical Engineering 03/2003; · 0.20 Impact Factor