Linked significant tree wavelet-based image compression

This paper proposes a new linked significant tree (LST) wavelet coding method for improved compression of images. The proposed method first links all the significant coefficients together within a wavelet tree to facilitate encoding algorithm. Insignificant parents, with at least one significant child found in the wavelet data, are changed to significant to link them together. Their location is saved for identification, and they are then treated just like any other significant coefficients during encoding. An embedded LST encoding algorithm is proposed to accommodate the processed output for better coding efficiency. It exploits the fact that no descendent of an insignificant coefficient can be significant any more, since all the significant coefficients within a wavelet tree are linked together. This fact eliminates the need to check the descendents of those coefficients that are found as insignificant. Locations of converted coordinates are sent to the decoder after each encoding pass, to change the values back to original during reconstruction. The proposed method shows improvement when applied to gray-scale images.