サブブロック輝度シフトを用いたフラクタル画像符号化

Abstract

This paper presents an improved fractal block coding scheme for still images. The proposed scheme employs a new technique which we call "sub-block luminance level shifting." In fractal block coding, an input image is first partitioned into range blocks. Each range block is encoded by a set of contractive affine transformations of its corresponding domain block. One of the coded data for each range block is an average pixel value of the range block, which is used for luminance level shifting between the range block and the contracted domain block. In our proposed method, a range block is further partitioned into sub-blocks in some cases and an average value of each sub-block instead of the range block is used for luminance level shifting. We have proposed an improved fractal block coding scheme applying this sub-block luminance level shifting adaptively block-by-block basis and also combining this method with adaptive range block size fractal coding. The computer simulation results show that the proposed fractal coding scheme gives higher SNR (Signal-to-Noise Ratio) values and better image qualities compared to the conventional fractal block coding scheme.