Fractal coding of subbands using an oriented partition

In this paper, we propose a new image coding scheme based on fractal coding of the coefficients of a wavelet transform, in order to take into account the self-similarity observed in each subband. The original image is first decomposed into subbands containing information in different spatial directions and at different scales, using Finite Impulse Response filters. Subbands are encoded using Local Iterated Function Systems (LIFS), with range and domain blocks presenting horizontal or vertical directionalities. Their sizes are defined according to the correlation lengths in each subband. The proposed method is applied on standard test images, distortion vs rate is compared with the algorithm proposed in [1] for fractal coding of the whole image. We also discuss about the distortion vs rate improvement obtained on high frequency subbands when using fractal coding instead of pyramidal vector quantization [2,3].