Switching wavelet transform for ROI image coding
In region-of-interest (ROI) image coding based on wavelet transforms, the tap length of the wavelet filter as well as energy compaction characteristics affect the quality of the restored image. This paper presents a wavelet transform comprised of two wavelet filter sets with different tap lengths. The wavelet filter is switched to the shorter-length set to code a ROI of an image and to the longer-length one for the remaining region, the region of non-interest (RONI). ROI coding examples demonstrate that this switching wavelet transform provides better quality levels than fixed transforms under the same total bits; the quality of the recovered ROI is improved in the lossy coding of both regions while that of the full image is improved in the lossless coding of the ROI.
wavelet transform roi coding image compression lifting scheme