Modern perceptual image coders reach impressively high subjective quality even at low bit-rates but tend to denoise or "detexturize" the coded pictures. Traditionally, two independent parametric approaches, ...
详细信息
ISBN:
(纸本)9781538660959
Modern perceptual image coders reach impressively high subjective quality even at low bit-rates but tend to denoise or "detexturize" the coded pictures. Traditionally, two independent parametric approaches, known as texture and film grain synthesis, have been applied in the spatial domain as pre and post-processors around the codec to counteract such effects. In this work, a unified alternative, operating directly within the spectral domain of conventional transform codecs with tight coupling to the transform coefficient quantizer, is proposed. Due to its design, this spectrally adaptive noise filling tool (SANFT) enables highly input adaptive realizations by reusing the coder's existing optimized spatial and spectral partitioning algorithms. Formal subjective evaluation in the context of a "main still picture" High Efficiency Video coding (HEVC) implementation confirms the benefit of the proposal.
Several well-known methods for lossy compression of stillimages are here analyzed to evaluate their performance for hyperspectral images. The lossy compression methods discussed are the JPEG standard, and four approa...
详细信息
ISBN:
(纸本)081944667X
Several well-known methods for lossy compression of stillimages are here analyzed to evaluate their performance for hyperspectral images. The lossy compression methods discussed are the JPEG standard, and four approaches based on the Wavelet Transform: the Embedded coding of ZeroTree wavelet coefficients, the Set Partitioning in Hierarchical Trees, a Lattice Vector Quantizer, and the new JPEG2K. Experiments are first performed on corpuses of natural grayscale stillimages to provide a general framework of the performance of each method. Then experiments are performed on several hyperspectral images taken with CASI and AVMS sensors. Experiments show that it is possible to employ the basic lossy compression methods for hyperspectral imagecoding. The wavelet-based approaches produce results consistently better than the JPEG: JPEG can not achieve compression ratios above 75: 1;on the other side, with EZT, SPIHT and LVQ compression ratios of 250:1 or higher may be reached. For JPEG2K, higher compression ratios than JPEG may also be reached, but with a PSNR quality lower than the three other techniques. At compression ratios about 8: 1, the wavelet methods yield results 1.5 dB better than those of JPEG. These results help to explain why JPEG2K standard uses the WT instead of the DCT.
暂无评论