The Application Of Adaptive Lifting Wavelet Transform In The Underwater Acoustic Image Compression

With the fast development of wavelet in field of Image compressing, the investigations of imaging sonar also have a great advancement. As the second generation wavelet, the lifting wavelet not only inherits the characteristic of the first generation wavelet, but also independent on Fourier transform and easy to build on nonlinear wavelet transforms(such as integer wavelet transforms) as well as fits for adaptive.The traditional wavelet which can not change with the input signals, combined with the constraints of UWA communication channel and sonar imaging principle and so on, leading to the processing of some images with sharp edges,piecewise smooth and singularity are not ideal. To solve problems above and obtain an ideal underwater image coding method, the paper is started with the promotion of the wave nature, promoted a lifting scheme of adaptive wavelet combined by the actual situation. Through comprehensive comparison, the algorithm can make full use of adaptive characteristics to achieve the purpose of keeping the image edges and reducing the wavelet coefficients without any overhead cost. Meanwhile, a wavelet structure with updating before forecast is adopted by the algorithm to ensure the stability of wavelet transform. Update step precedes doesn't affect prediction step(next transform) in this framework and therefore is more suitable for the application and processing. With the conjunction of SPIHT algorithm can achieve specific acoustic image compression.Base on discussion, we simulate imaging sonar compressing by dint of Matlab. With the contrast and analyze, the algorithm can reduce wavelet coefficients, and also can increase condensation rate, and to make sure stability. The algorithm has a worthiness to generalize in the filed of imaging sonar.