Hybrid Screening Algorithm Based on Image Toning

The hybrid screening algorithm is a half toning method, in which mid-tones consist of periodic clustered amplitude modulated (AM) dots, and highlights or dark tones use stochastic dispersed frequency modulated (FM) dots. Because AM and FM screens have different characteristics, the abrupt disjuncture among the dots will appear in the transition areas of different tones. Simultaneously, moire fringes are caused by the periodic texture of the AM dots, and problems such as dot loss are caused by small dots within the FM dot. In this paper, the stochastic center algorithm for AM dots and the multilevel error diffusion recombination algorithm for FM dots are proposed to solve these problems. Combining the two algorithms would effectively solve the problem of uneven connections between different tones. The experimental results show that the proposed algorithm solves the problems mentioned above and effectively controls the dot’s total perimeter and the dot’s expansion. Therefore, the algorithm has a better ability to reproduce the original image and is an effective hybrid halftone method.