A hybrid lossless compression scheme using region-based predictive coding and integer wavelet transform

This paper presents a hybrid scheme for lossless compression of the X-ray non-destructive testing (NDT) images of aircraft components. The method combines predictive coding and integer wavelet transform (IWT). Furthermore, with the aid of component CAD models to divide the X-ray images of aircraft components into different regions based on the material structures, the design of the predictors and the choice of the IWT are optimised according to the specific image features contained in each region having the same material structure. Using a real X-ray image of a practical aircraft component, the proposed hybrid scheme is presented and shown to offer a significantly higher compression ratio than other lossless compression schemes.