Processing of wavelet transform data for improved image compression

Abstract

This paper presents a novel preprocessing technique of wavelet transform data to link all the significant coefficients together, in order to facilitate the image coding algorithms for increased compression. The proposed algorithm finds the isolated significant coefficients in the wavelet transformed data for current threshold value. All the insignificant coefficients in the wavelet tree that lies above that isolated significant coefficient (i.e., its insignificant parents) are changed to significant coefficients and their location is saved, they are then treated just like other significant coefficients. Coding algorithms have been modified to accommodate the processed output. In the end, algorithm indicates converted coordinates that are used to change the value back to original during reconstruction. Noticeably high compression ratio is achieved for most of the images, when the proposed method is used with the modified image codecs.