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Listless set partitioning embedded block (LSK) and set partitioning embedded block (SPECK) are known for their low complexity and simple implementation. However, the drawback is that these block-based algorithms encode each insignificant subband by a zero. This generates many zeros at earlier passes because the number of significant coefficients at higher bitplanes is likely to be very few in a transformed image. An improved LSK (ILSK) algorithm that codes a single zero to several insignificant subbands is proposed. This reduces the length of the output bit string, encoding/decoding time and dynamic memory requirement at early passes. Furthermore, ILSK algorithm is coupled with discrete Tchebichef transform (DTT). This gives rise to a novel coder named as hierarchical listless DTT (HLDTT). The proposed HLDTT has desirable attributes like full embeddedness for progressive transmission, precise rate control for constant bit rate traffic and low complexity for low power applications. The performance of HLDTT is assessed using peak-signal-to-noise-ratio (PSNR) and structural-similarity-index-metric (SSIM). Extensive simulation conducted on various standard test images shows that HLDTT exhibits significant improvement in PSNR values from lower to medium bit rates. At the same time, HLDTT shows improvement in SSIM values on all bit rates.

The hyperspectral image provides rich spectral information content, which facilitates multiple applications. With the rapid advancement of the spatial and spectral resolution of optical instruments, the image data size has increased by many folds. For that, it requires a compression algorithm having low coding complexity, low coding memory demand and high coding efficiency. In recent years, many coding algorithms are proposed. The wavelet transform-based set-partitioned hyperspectral compression algorithms have superior coding performance. These algorithms employ linked lists or state tables to track the significant/insignificant of the partitioned sets/coefficients. The proposed algorithm uses the pyramid hierarchy property of wavelet transform. The markers are used to track the significance/insignificance of the pyramid level. A single pyramid level has many sets. An insignificant pyramid level having multiple sets is represented as a single bit in proposed compression algorithm, while a single insignificant set in 3D Set Partition Embedded bloCK (3D-SPECK) and 3D-Listless SPECK (3D-LSK) is represented as a single bit. Through this, the requirement of the bits in the proposed algorithm is less than other wavelet transform compression algorithms at the high bit planes. The simulation result shows that the proposed compression algorithm has high coding efficiency with very less coding complexity and moderate coding memory requirement. The reduced coding complexity improves the performance of the image sensor and lowers the power consumption. Thus, the proposed compression algorithm has great potential in low-resource onboard hyperspectral imaging systems.

This paper presents a listless variant of a modified three-dimensional (3D)-block coding algorithm suitable for medical image compression. A higher degree of correlation is achieved by using a 3D hybrid transform. The 3D hybrid transform is performed by a wavelet transform in the spatial dimension and a Karhunen–Loueve transform in the spectral dimension. The 3D transformed coefficients are arranged in a one-dimensional (1D) fashion, as in the hierarchical nature of the wavelet-coefficient distribution strategy. A novel listless block coding algorithm is applied to the mapped 1D coefficients which encode in an ordered-bit-plane fashion. The algorithm originates from the most significant bit plane and terminates at the least significant bit plane to generate an embedded bit stream, as in 3D-SPIHT. The proposed algorithm is called 3D hierarchical listless block (3D-HLCK), which exhibits better compression performance than that exhibited by 3D-SPIHT. Further, it is highly competitive with some of the state-of-the-art 3D wavelet coders for a wide range of bit rates for magnetic resonance, digital imaging and communication in medicine and angiogram images. 3D-HLCK provides rate and resolution scalability similar to those provided by 3D-SPIHT and 3D-SPECK. In addition, a significant memory reduction is achieved owing to the listless nature of 3D-HLCK.

This study proposes an efficient algorithm for colour image compression with listless implementation based on set partition block embedded coding (SPECK). The objective of this work is to develop an algorithm that exploits the redundancy in colour spaces, low complexity quadtree partitioning and reduced memory requirements. Colour images are first transformed into luminance chrominance (YCbCr) planes and a wavelet transform is applied. A reduction of the memory requirement is achieved with the introduction of a state marker that matches each colour plane to eliminate the list with dynamic memory in the original colour SPECK coder (CSPECK). The wavelet coefficients are scanned using Z-order that matches the subband decompositions. The proposed algorithm then encodes the de-correlated colour plane as one unit and generates a mixed bit stream. The linear indexing and initial state marker are modified to jointly test the chrominance plane together. Composite colour coding enables precise control of the bit rate. The performance of the proposed algorithm is comparable with CSPECK, set partitioning in hierarchical trees (SPIHT) and JPEG2000 but with less memory requirements. For progressive lossless, a saving of more than 70% than final working memory against CSPECK and SPIHT highlights the benefit of the proposed algorithm.