一类小波的构造方法研究法

W.Sweldens指出提升框架可以由已知小波滤波器构造新的满足特定性能的小波滤波器,本文在其工作的基础上,给出了构造一类双正交小波的具体实现算法,以CDF(1,3)小波为例进行了说明,并应用于数据压缩,仿真结果表明该方法构造的小波具有优良的压缩性能。     

航空图像压缩的双正交小波滤波器整数化设计

在航空图像压缩中,通常采用具有线性相位、正则性、消失矩和完全重构,及适于硬件实现、实时等特性的小波。根据小波滤波器设计,提出了一种基于图像压缩的构造整数双正交小波滤波器的设计方法。从选择小波基的原则为出发点,以CDF9-7小波基为参考,以压缩效果为准则来构造出更优的双正交整数小波基,并且采用航空图像为标准训练图像,以压缩比、峰值信噪比、压缩后保留能量百分比为参数,来寻找最优的小波基。试验结果证明,此方法可以实施非常简单的、无浮点乘法的运算,因而减少运算复杂性以及降低小波硬件实现的难度。     

对称—反对称多小波滤波器组的参数化构造及其在图像压缩中的应用

本文给出了一类对称—反对称多小波滤波器组参数化设计方法,并在此基础上提出了新的多小波零树编码方案.实验表明,与常用的9-7单小波相比,我们所设计的双正交对称—反对称多小波可使编码性能有较大幅度的改善.     

新型9/7小波基构造及快速实现

CDF9/7小波的复杂系数是限制其快速实现的主要因素。该文构造了新的含参双正交提升小波模型,并利用能量集中性法则和迭代搜索算法提出一种压缩性能与此相当适合移位操作的有理数小波基。新小波基在硬件实现时可用一次移位和加法运算代替乘法运算,运算量仅为原来的25%,且无需考虑位长对精度的影响。一维小波4级流水架构已通过FPGA验证,与同类设计相比,减少一半的资源消耗量,并且大幅提高系统的工作频率。     

纯二维小波滤波器组及其在图像压缩中的应用

构造了一组新的纯二维不可分离的小波滤波器——全相位离散反余弦列率滤波器（APDICSF）。该滤波器具有五株排列的交错采样形式和良好的内插性能,适用于图像分解压缩。将其用于提升格式的预测和更新滤波器,得到与可分离小波滤波器组不同的图像分解方式,并用SPIHT实现图像的压缩编码。实验证明,APDICSF组的压缩效果好于经典的Neville滤波器,在图像压缩方面有良好的应用前景。     

提升格式的小波变换及在视频压缩中的应用

提升方法是计算离散小波变换的有效手段，将提升三维小波变换用于视频信号压缩。时间方向小渡变换选用Haar滤波器组，空间小波变换则在常规的图像编码所常用的D9/7滤波器组基础上，对其参数进行调整，进一步减少运算量。实验表明这种调整取得了与D9/7双正交小波基本一致图像编码效果，但提高了运算速度。     

32bit定点定值小数乘法器的算法优化及实现

小波理论和分析方法极大地促进了应用科学研究。应用领域包括:数学领域的许多学科;信号分析、图像处理;量子力学、理论物理;军事电子对抗与武器的智能化;计算机分类与识别;音乐与语言的人工合成;医学成像与诊断;地震勘探数据处理;大型机械的故障诊断等方面。CDF9/7小波更是图像编解码的首选变换核。它使用到了大量的小数乘法器,然而传统的滤波器结构都是把乘法器看成一个整体来设计,导致流水线不够深,以至于处理速度达不到很高的层次。文章首先对CDF9/7小波变换式进行变换,得到一个并行结构,并且对每一个乘法器使用Wallace Tree和CLA相结合的实现方法进行设计。最后通过仿真、功能验证和逻辑综合,证明该设计功能稳定,并且在速度上有很大的提升。     

基于CDF9-7小波和自适应Otsu算法的视频字幕分割

提出了一种基于CDF9-7小波和自适应Otsu算法的视频图像字幕分割算法。首先从视频中截取视频图像,并对其进行灰度化等预处理,其次对预处理后的图像进行CDF9-7小波变换,获取其水平和垂直的高频分量HH,然后使用自适应Otsu算法分割出该高频分量图像中的字幕区域。实验表明,该算法分割效果良好,具有一定的鲁棒性和自适应性。以这些区域为基础,可以进一步完成诸如视频字幕识别等图像分析、理解和识别操作。     

基于加权小波分析和神经网络的人脸识别

基于加权小波分析和神经网络提出一种新的准正面人脸识别算法.二维的小波分解具有对表情变化不敏感的特点,可很好地压缩和表征人脸图像的特征,再加上变换后高频的人脸特征,能很好地表达人脸特征;径向基网络作为分类器有很好的推广性能,有利于大容量样本的分类.在对人脸库ORL和YEL的识别实验中,与传统算法相比有很高的识别速度和识别率.     

小波变换码中滤波器的选择

在本文中，我们从广义编码增益、分解重构性能与对误差的敏感性、编码性能与主观质量三个方面对双正交小波12／4、9／7与9／3进行比较，得出：双正交小波12／4比9／7与9／3更适合于小波图像压缩，特别是在高保真压缩中；在低比特率编码中，双正交小波12／4与9／7相差不大。     

A new flexible bi-orthogonal filter design for multiresolutionfilterbanks with application to image compression

We propose a new fast method with great potential for multiresolution pyramid decomposition of signals and images. The method allows unusual flexibility in choosing a filter for any task involving the multiresolution analysis and synthesis. Using our method, one can choose any low-pass filter for the multiresolution filtering. This method enabled us to choose the best filters for set partitioning in hierarchical trees (SPIHT) image compression for the corresponding support sizes. The compression results for our seven tap filters are better than those of the 9/7 wavelet filters and approximately the same as those of the 10/18 filters, while at the same time our seven tap filters are faster than 10/18 filters     

A new class of biorthogonal wavelet systems for image transformcoding

We construct general biorthogonal Coifman wavelet systems, a new class of compactly supported biorthogonal wavelet systems with vanishing moments equally distributed for a scaling function and wavelet pair. A time-domain design method is employed and closed-form expressions for the impulse responses and the frequency responses of the corresponding dual filters are derived. The resulting filter coefficients are all dyadic fractions, which is an attractive feature in the realization of multiplication-free discrete wavelet transform. Even-ordered systems in this family are symmetric, which correspond to linear-phase dual filters. In particular, three filterbanks (FBs) in this family are systematically verified to have competitive compression potential to the 9-7 tap biorthogonal wavelet FB by Cohen et al. (1992), which is currently the most widely used one in the field of wavelet transform coding. In addition, the proposed FB's have much smaller computational complexity in terms of floating-point operations required in transformation, and therefore indicate a better tradeoff between compression performance and computational complexity.     

纯二维全相位滤波器组及其在图像压缩中的应用

基于全相位理论,设计了3种纯二维全相位滤波器组(ADFB).这些滤波器组可以直接对图像进行纯二维分解和重构,若忽略滤波器的有限精度问题,系统是全重建的.为了减小运算量,纯二维ADFB采用提升格式实现.仿真试验表明,纯二维ADFB具有良好的数据压缩特性.在压缩率相同的情况下,尤其是IDCT-AFB7.7比Daubechies9/7小波重建图像的峰值信噪比(PSNR)最多小0.7 dB,这与采用的适合于可分离二维小波变换的四叉树SPIHT编码方案有关,若采用二叉树SPIHT编码,会使压缩效果得到改善.     

Multiresolution time-domain algorithm using CDF biorthogonalwavelets

A new approach to the multiresolution time-domain (MRTD) algorithm is presented in this paper by introducing a field expansion in terms of biorthogonal scaling and wavelet functions. Particular focus is placed on the Cohen-Daubechies-Feauveau (CDF) biorthogonal-wavelet class, although the methodology is appropriate for general biorthogonal wavelets. The computational efficiency and numerical dispersion of the MRTD algorithm are addressed, considering several CDF biorthogonal wavelets, as well as other wavelet families. The advantages of the biorthogonal MRTD method are presented, with emphasis on numerical issues     

Biorthogonal nearly coiflet wavelets for image compression

Filter bank design for wavelet compression is crucial; careful design enables superior quality for broad classes of images. The Bernstein basis for frequency-domain construction of biorthogonal nearly coiflet (BNC) wavelet bases forms a unified design framework for high-performance medium-length filters. A common filter bandwidth is characteristic of widely favoured BNC filter pairs: the classical CDF 9/7, the Villasenor 6/10, and the Villasenor 10/18. Based on this observation, we construct previously unknown BNC 17/11 and BNC 16/8 wavelet filters. Key filter-quality evaluation metrics, due to Villasenor, demonstrate these filters to be well suited for image compression. Also studied are the biorthogonal coiflet 17/11 (half-band), 18/10 and 10/6 filter pairs, which have not previously been formally evaluated for image coding. Simulation results confirm that the BNC 17/11 and BNC 16/8 wavelet bases are outstanding for compression of natural and medical images, and particularly for images with significant high-frequency detail, such as fingerprints. The BNC 17/11 pair recommends itself for international standardization for the compression of still images; the BNC 16/8 pair for high-quality compression of production quality video. Experimental evidence suggests biorthogonal filters achieve good compression if, subject to a filter bandwidth constraint, maximum vanishing moments are obtained for a given filter support.     

New filter banks and more regular wavelets

One of the most interesting features of a wavelet is its Sobolev regularity. In this paper, we construct new wavelets that are more regular than the Daubechies wavelets for a given support width. We tabulate the coefficients of the new filters to make them easily accessible. We show that these filters outperform the Daubechies filters in the L² approximation of the ideal filter. An application for speech analysis, synthesis, and compression is provided     

New image compression techniques using multiwavelets andmultiwavelet packets

Advances in wavelet transforms and quantization methods have produced algorithms capable of surpassing the existing image compression standards like the Joint Photographic Experts Group (JPEG) algorithm. For best performance in image compression, wavelet transforms require filters that combine a number of desirable properties, such as orthogonality and symmetry. However, the design possibilities for wavelets are limited because they cannot simultaneously possess all of the desirable properties. The relatively new field of multiwavelets shows promise in obviating some of the limitations of wavelets. Multiwavelets offer more design options and are able to combine several desirable transform features. The few previously published results of multiwavelet-based image compression have mostly fallen short of the performance enjoyed by the current wavelet algorithms. This paper presents new multiwavelet transform and quantization methods and introduces multiwavelet packets. Extensive experimental results demonstrate that our techniques exhibit performance equal to, or in several cases superior to, the current wavelet filters.     

Design of IIR orthogonal wavelet filter banks using lifting scheme

The lifting scheme is well known to be an efficient tool for constructing second generation wavelets and is often used to design a class of biorthogonal wavelet filter banks. For its efficiency, the lifting implementation has been adopted in the international standard JPEG2000. It is known that the orthogonality of wavelets is an important property for many applications. This paper presents how to implement a class of infinite-impulse-response (IIR) orthogonal wavelet filter banks by using the lifting scheme with two lifting steps. It is shown that a class of IIR orthogonal wavelet filter banks can be realized by using allpass filters in the lifting steps. Then, the design of the proposed IIR orthogonal wavelet filter banks is discussed. The designed IIR orthogonal wavelet filter banks have approximately linear phase responses. Finally, the proposed IIR orthogonal wavelet filter banks are applied to the image compression, and then the coding performance of the proposed IIR filter banks is evaluated and compared with the conventional wavelet transforms.