Image coding based on fractal approximation and vector quantization

We propose a coding algorithm for still images using fractal approximation and vector quantization (VQ). The conventional fractal coding algorithms indirectly used the gray patterns of an original image with contraction mapping, whereas the proposed fractal coding method employs a previously approximated image as a domain pool and uses its gray patterns. Thus, the proposed algorithm employs fractal approximation without the constraint of contraction mapping. To approximate an original image, we use an orthogonal polynomial transform and to encode the transform coefficients we employ VQ. Also, for variable block-size segmentation, we use the fractal dimension that represents the similarity of regions in a block and the roughness of the gray surface of a region. Computer simulations with several test images show that the proposed method shows better performance than the conventional fractal coding methods for encoding still pictures