Digital multitoning with overmodulation for smooth texture transition

Abstract

Multilevel halftoning (multitoning) is an extension of bitonal halftoning, in which the appearance of intermediate tones is created by the spatial modulation of more than two tones, i.e., black, white, and one or more shades of gray. In this paper, the conventional multitoning approach and a previously proposed approach, both using stochastic screen dithering, are investigated. A human visual model is employed to measure the perceived halftone error for both algorithms. The performance of each algorithm at gray levels near the printer's intermediate output levels is compared. Based on this study, a new overmodulation algorithm is proposed. The multitone output is mean preserving with respect to the input and the new algorithm requires little additional computation. It will be shown that, with this simple overmodulation scheme, we will be able to manipulate the dot patterns around the intermediate output levels to achieve desired halftone patterns. Implementation issues related to optimal output level selection and inkjet-printing simulation for this new scheme will also be reported.

Tone-Replacement Error Diffusion for Multitoning

“…2) M-BN: Blue-noise multitoning [13], adopting the first concentration for 3-level in their study, and the concentrations for other q-level are generated using M-DBS single tone patterns. 3) M-OD: Ordered dithering for multitoning with overmodulation using dither array [15] of size 32 × 32. 4) M-ODLA: Lin and Allebach [12] proposed a multitoning based on the ordered dithering using dither matrix of size 128 × 128, and the parameter d is set at 4 for the following experiments.…”

“…Figure 1 shows the results of the M-OD [15] with a ramp image. As it can be seen, the banding artifact arises when a region is of similar pixel values which are close to one of the quantization levels.…”

“…The banding effect is abrupt and unnatural for human perception. In Yu et al's study [15], the reason how this banding interferes visual perception was discussed. To ease this artifact, the over-modulation scheme was proposed, and the corresponding result is shown in Fig.…”

“…5(e). Subsequently, they proposed an over-modulation preprocessing [15] to solve this problem as shown in Fig. 5(f).…”

Data Hiding in Non-Expansion Visual Cryptography Based on Edge Enhancement Multitoning

“…Here we adopted the conventional multitoning scheme in the paper which is a simple extension of stochastic screen dithering for devices with multiple output levels [10]. It has edge enhancement properties to some extent.…”