Improvements in or relating to encoding a portion of a digital image

摘要

The invention provides a method of encoding a portion of a digital image (a child block) by identifying a feature or features within the child block. A larger portion of the image (a parent block) is then created such that it encompasses the child block. The exact position of the parent block relative to the child block is dependant on the feature or features identified within the child block. Once the position of the parent block has been chosen, the parent block is mapped onto the child block to provide a fractal term for the mapping. One advantage of this method is that the decoder deduces the offset parameters for the local fractal transform from the basis functions alone, by inferring the dominant edge position, so that no offset information is required. This means that greater compression ratios can be achieved. The invention can be used to either encode a complete image, giving increased compression ratios, or to enhance the edge information with an image encoded using any block based coder method.