Wavelet based adaptive block parallel vector error diffusion for colour image halftone

In this paper, a block parallel vector error diffusion method has been proposed and illustrated for fast error diffusion halftoning of colour images. To reduce the colour artifacts arising due to block processing, an adaptive block error diffusion filter has been used. The adaptive block error diffusion filter has been implemented using Kronecker matrix multiplication and normalized least mean square algorithm. The proposed adaptive block error diffusion filter takes care of the relations between the three colour planes. Better sharpness control and edge enhancement has been achieved with the aid of wavelet processing. The results of the block processing are provided and the possible scopes of trade-offs are discussed.