Research on Pseudo-Contour of Halftone Images Based on Multi-level Error Diffusion Algorithm

To research the distribution characteristics of pseudo-contour in Multi-level Error Diffusion(MED) halftone images,based on the analysis of generation mechanism of MED,three images which were partial bright,normal and dark separtely,were processed by multi-level error diffusion halftoning algorithm with different quantization threshold values. The compared results showed that pseudo-contour related with the gradual level distribution of the images and quantization threshold values.On this basis,a new method was put forward to modulate the quantization threshold values in midtones where pseudo-contour appeared obviously.The calculating results showed that it is effective to eliminate the pseudo-contour in multi-level error diffusion halftone images.