Efficient architectures for two-dimensional discrete wavelet transform using lifting scheme

Mapping Long-Term Spatiotemporal Dynamics of Pen Aquaculture in a Shallow Lake: Less Aquaculture Coming along Better Water Quality

Pen aquaculture is the main form of aquaculture in some shallow lakes in eastern China. It is valuable to map the spatiotemporal changes of pen aquaculture in eutrophic lakes to assess its effect on water quality, thereby helping the relevant decision-making agencies to manage the water quality (WQ) of lakes. In this study, an automatic approach for extracting the pen aquaculture area was developed based on Landsat data. The approach integrates five algorithms, including grey transformation, discrete wavelet transform, fast Fourier transform, singular value decomposition and k-nearest neighbor classification. It was successfully applied in the automatic mapping of the pen aquaculture areas in Lake Yangcheng from 1990 to 2016. The overall accuracies were greater than 92%. The result indicted that the practice of pen aquaculture experienced five stages, with the general area increasing in the beginning and decreasing by the end of the last stage. Meanwhile, the changes of nine WQ parameters observed from 2000 to 2016, such as ammonia (NH3-N), pH, total nitrogen (TN), total phosphorus (TP), chlorophyll a, biochemical oxygen demand (BOD), chemiluminescence detection of permanganate index (CODMn), Secchi disk depth (SDD) and dissolved oxygen (DO), were analyzed in the lake sectors of Lake Yangcheng, and then their relationships were explored with the percentage of pen aquaculture area. The result suggested that the percentage of pen aquaculture area exhibits significantly positive correlations with NH3-N, TN, TP, chlorophyll a, BOD and CODMn, but significantly negative correlations with SDD and DO. The experimental results may offer an important implication for managing similar shallow lakes with pen aquaculture expansion and water pollution problems.

A Parallel Algorithm for Wavelet Transform-Based Color Image Compression

Wavelet transforms emerge as one of the popular techniques in image compression. This technique is accepted by the JPEG Committee for the next-generation image compression standard JPEG-2000. Convolution-based strategy is widely used in calculating the wavelet transform of the image. A convolution-based wavelet transform consists of a large number of multiplications and additions. A color image consists of a two-dimensional matrix each for red, green, and blue colors. An ordinary way to calculate the wavelet transform of a color image includes calculating the transform of the intensity matrix of the red, green, and blue components. In this article, we present a parallel algorithm for calculating the convolution-based wavelet transform of the red, green, and blue intensity components simultaneously in color images, which can run on commonly used processors. This means that it needs no extra hardware. The results are also compared to the nonparallel algorithm based on compression time, mean square error, compression ratio, and peak signal-to-noise ratio. Complexity analysis and comparative complexity analysis with some other papers are also shown here.

Precision-aware self-quantizing hardware architectures for the discrete wavelet transform

This paper presents designs for both bit-parallel (BP) and digit-serial (DS) precision-optimized implementations of the discrete wavelet transform (DWT), with specific consideration given to the impact of depth (the number of levels of DWT) on the overall computational accuracy. These methods thus allow customizing the precision of a multilevel DWT to a given error tolerance requirement and ensuring an energy-minimal implementation, which increases the applicability of DWT-based algorithms such as JPEG 2000 to energy-constrained platforms and environments. Additionally, quantization of DWT coefficients to a specific target step size is performed as an inherent part of the DWT computation, thereby eliminating the need to have a separate downstream quantization step in applications such as JPEG 2000. Experimental measurements of design performance in terms of area, speed, and power for 90-nm complementary metal-oxide-semiconductor implementation are presented. Results indicate that while BP designs exhibit inherent speed advantages, DS designs require significantly fewer hardware resources with increasing precision and DWT level. A four-level DWT with medium precision, for example, while the BP design is four times faster than the digital-serial design, occupies twice the area. In addition to the BP and DS designs, a novel flexible DWT processor is presented, which supports run-time configurable DWT parameters.