Radiological image compression using wavelet transform with arithmetic coding
Pongskorn Saipetch, Bruce K. T. Ho, Marco Ma, Keh‐Shih Chuang, Jun Wei · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1994
We have developed a compression algorithm based on discrete wavelet transform (DWT) and arithmetic coding (AC) that satisfies the requirements of a radiological image archive. This new method is far superior to the previously developed full frame DCT (FFDCT) method as well as the industrial standard JPEG. Since DWT is localized in both spatial and scale domains, the error due to quantization of coefficients does not propagate throughout the reconstructed picture as in FFDCT. Since it is a global transformation, it does not suffer the limitation of block transform methods like JPEG. The severity of error as measured by NMSE and maximum difference increases very slowly with compression ratio compared to FFDCT. Normalized nearest neighbor difference (NNND), which is a measure of blockiness, stays approximately constant, while JPEG's NNND increases rapidly with compression ratio. Furthermore, DWT has an efficient FIR implementation which can be put in parallel hardware. DWT also offers total flexibility in the image format; the size of the image does not have to be a power of two as in the case of FFDCT.