Data compression using wavelet transformation; tree pruning

摘要

Data, such as image data, to be compressed first undergoes wavelet transformation to produce a plurality of layers (H1 to H5) each having a different resolution. Each lowest resolution datapoint (layer H5) may be considered as having tree comprising a plurality of descendent datapoints at higher resolutions (H2 to H5); the lowest resolution data points may be considered as forming a forest of trees. To compress the data branches of trees having datapoints with low information content (ie below a threshold) are pruned from the tree structure and only the remaining data - figure 5B(i) - transmitted or stored. Datapoints below the threshold may be set to zero before pruning; zero-crossings may also be pruned from the tree. <IMAGE>