Digital image halftoning by noise thresholding

Approaches for digital halftoning of images using dithering threshold the input image with additive dithering noise. The paper presents a technique which thresholds the noise directly. The threshold is modified at each step such that the expected value of the output is equal to the input pixel´s gray value. Further, error feedback is used to correct the threshold. Tests on images show the method´s ability to retain features in the high frequency regions such as edges as well as low frequency features such as slow variations in intensity. One advantage the proposed method is its very general nature since it offers a wide choice of the three filters: noise shaping filter, feedforward filter and feedback filter