輝度・色差成分間の相関を利用したカラー画像のサブバンド・フラクタル符号化

Abstract

This paper proposes a new efficient fractal coding scheme for color images and demonstrates its simulation experimental results. The proposed scheme utilizes the correlation between a luminance component (Y) and two color difference components (C_b, C_r) in the fractal coding. It also employs subband decomposition and vector quantization. Each input component (Y, C_r, or C_b) is first divided into 7 subband images. The fractal block coding for Y, Cr and C_b is carried out only for the lowest frequency subband images. For the other higher frequency subband images, vector quantization (VQ) is carried out. The fractal coded data of Y, except for the range block average pixel values, are applied to fractal coding of Cr and C_b. Therefore only the range block average pixel values are coded for C_r and C_b. In order to enhance the coding performance further more, the residual differences between the original and reconstructed low frequency subband images are quantized and entropy coded. Computer simulation experiments were carried out in order to evaluate the proposed coding scheme. The results show that the proposed scheme gives better performance compared to the conventional fractal block coding scheme which encodes Y, C_r and C_b independently. The proposed scheme also outperforms the JPEG coding scheme.