共查询到20条相似文献,搜索用时 187 毫秒
1.
在深入分析Shearlet变换理论的基础上,给出具体的Shearlet变换步骤,并提出一种针对图像脉冲噪声的混合滤波方法.该方法首先对噪声图像进行Shearlet多尺度变换,获得高频和低频系数,保留低频系数不变;然后针对Shearlet高频系数能够较好地刻画噪声局部化的性质,设计出一种多尺度、多方向特性的串/并联自适应中值滤波器,对高频系数中噪声进行自适应检测和滤除;最后实现低频系数和滤波后高频系数重构.通过与小波阈值法去噪和开关中值滤波法仿真实验比较可知,该滤波方法对于高强度的脉冲噪声具有较好的处理效果. 相似文献
2.
针对传统小波去噪时图像边缘被破坏因而丢失有用细节信息的问题,基于小波去噪的优点,研究了几种改进的基于小波变换的图像去噪方法。分别是基于小波变换和中值滤波的去噪方法,雏纳滤波和小波域滤波相结合的方法,小波变换去噪与高阶统计量滤波法去噪相结合的方法等。经过大量的计算机仿真试验,最后所得结果表明这几种改进后的基于小波变换的去噪方法均可以有效地降低图像的噪声干扰,比较好地保留图像中重要的细节信息,具有一定的实际应用价值。 相似文献
3.
4.
5.
脊波变换是在小波变换的基础上提出的多尺度分析方法,对于图像中直线状和超平面的奇异性问题,脊波变换比小波变换有更好的处理效果。应用数字复合脊波变换去除嵌入在图像中的白噪声,并使用一个简单的复合脊波系数的硬阈值来实现。实验结果表明,这种算法比VisuShrink算法、普通脊波算法和Wiener 2滤波器图像去噪的去噪效果更好,同时复合脊波算法也能应用于图像去噪和模式识别特征提取。 相似文献
6.
7.
8.
基于经验模分解的小波阈值滤波方法研究 总被引:6,自引:2,他引:4
信号的多分辨经验模分解方法可以解释为以信号极值特征尺度为度量的时空滤波过程。这种时空滤波器充 分保留了信号本身的非线性和非平稳特征,在信号的滤波和去噪中具有较大的优势。本文提出了一种基于经验模分解的小 波阈值滤波去噪方法,并和小波阈值去噪、多尺度EMD滤波效果相比较。实验结果表明了基于经验模分解的小波阈值去 噪具有广泛的适用性和独特的去除非平稳信号的有色噪声的优势。 相似文献
9.
基于小波包变换的多阈值法语音信号去噪净化 总被引:1,自引:2,他引:1
文中在小波包变换和传统阈值法的基础上,提出了一种基于小波包变换的多尺度多阈值语音信号去噪净化方法。采用小波包分解,克服了传统的正交小波变换的缺陷。采用多尺度多阈值方法,通过改进噪声方差估计方法,在去噪的同时,进一步提高信噪比。仿真实验结果表明,本方法能有效去除信号中的噪声和较好保留语音细节,达到更佳的语音净化效果。 相似文献
10.
本文给出一种对小波变换模极大值进行自动滤波的算法.该算法可以自动寻找不同尺度之间对应同一边缘的模极大值,以实现非人工干预下的自动检测和去噪;并为采用小波变换模极大值法对边缘进行实时检测提供了可能性. 相似文献
11.
针对采用下采样滤波器结构的轮廓波、轮廓小波在图像去噪过程中会引入伪吉布斯现象,利用小波变换(WT)和非下采样方向滤波器组(NDFB)构造了一种新的多尺度、多分辨率图像的非下采样轮廓小波变换(NWCT)。WT去除了拉普拉斯金字塔滤波器(LPF)的计算冗余,NDFB保证了该变换具有平移不变性。为了验证该变换的有效性,对其进行了图像去噪实验。实验结果表明,所提出方法能获得比WT、轮廓波变换(CT)、轮廓小波变换(WCT)更高的峰值信噪比(PSNR),并且能够很好地抑制伪吉布斯现象。 相似文献
12.
Xin Wang 《IEEE transactions on image processing》2006,15(9):2771-2779
Image denoising is a lively research field. The classical nonlinear filters used for image denoising, such as median filter, are based on a local analysis of the pixels within a moving window. Recently, the research of image denoising has been focused on the wavelet domain. Compared to the classical nonlinear filters, it is based on a global multiscale analysis of images. Apparently, the wavelet transform can be embedded in a moving window. Thus, a moving window-based local multiscale analysis is obtained. In this paper, based on the Haar wavelet, a class of nonorthogonal multi-channel filter bank with its corresponding wavelet shrinkage called Lee shrinkage is derived. As a special case of this filter bank, the double Haar wavelet transform is introduced. Examples show that it is suitable for a moving window-based local multiscale analysis used for image denoising, edge detection, and edge enhancement. 相似文献
13.
This paper proposes a directional design method of 2-D nonseparable linear-phase paraunitary filter banks. The proposed method is based on a lattice structure consisting of the 2-D separable DCT block and nonseparable support extension processes. Because of the nonseparability, the bases are allowed to be directional with the critically fixed subsampling, overlapping, orthogonal, symmetric, real-valued, and compact support properties. First, a novel vanishing moment (VM) condition is introduced as a suitable directional constraint, where the moment is referred to as the trend VM. The condition forces wavelet filters, i.e., high-pass and bandpass filters, to annihilate trend-surface components. Second, some theoretical properties of TVMs are discussed for general 2-D paraunitary systems, and then, the properties are applied to the lattice parameters. In order to verify the significance, several design examples are shown, the trend-surface annihilation properties are numerically confirmed, and the denoising capability is evaluated for images through shrinkage. It is shown that our proposed transforms yield perceptually preferable results. 相似文献
14.
数字滤波器在语音信号处理中的应用 总被引:1,自引:0,他引:1
针对语音信号去噪的问题,设计了各种类型的IIR数字滤波器,然后用不同类型的滤波器处理不同的噪声,这改变了传统的一成不变的去噪方式.实验结果表明,同样的噪声用不同的滤波器处理,效果各有不同,经过分析,选出最优的滤波方式. 相似文献
15.
Most subsampled filter banks lack the feature of translation invariance, which is an important characteristic in denoising applications. In this paper, we study and develop new methods to convert a general multichannel, multidimensional filter bank to a corresponding translation-invariant (TI) framework. In particular, we propose a generalized algorithme à trous, which is an extension of the algorithme à trous introduced for 1-D wavelet transforms. Using the proposed algorithm, as well as incorporating modified versions of directional filter banks, we construct the TI contourlet transform (TICT). To reduce the high redundancy and complexity of the TICT, we also introduce semi-translation-invariant contourlet transform (STICT). Then, we employ an adapted bivariate shrinkage scheme to the STICT to achieve an efficient image denoising approach. Our experimental results demonstrate the benefits and potential of the proposed denoising approach. Complexity analysis and efficient realization of the proposed TI schemes are also presented. 相似文献
16.
On two-channel filter banks with directional vanishing moments. 总被引:1,自引:0,他引:1
The contourlet transform was proposed to address the limited directional resolution of the separable wavelet transform. One way to guarantee good approximation behavior is to let the directional filters in the contourlet filter bank have sharp frequency response. This requires filters with large support size. We seek to isolate the key filter property that ensures good approximation. In this direction, we propose filters with directional vanishing moments (DVM). These filters, we show, annihilate information along a given direction. We study two-channel filter banks with DVM filters. We provide conditions under which the design of DVM filter banks is possible. A complete characterization of the product filter is, thus, obtained. We propose a design framework that avoids 2-D factorization using the mapping technique. The filters designed, when used in the contourlet transform, exhibit nonlinear approximation comparable to the conventional filters while being shorter and, therefore, providing better visual quality with less ringing artifacts. Furthermore, experiments show that the proposed filters outperform the conventional ones in image approximation and denoising. 相似文献
17.
针对Contourlet变换在频谱混叠及平移不变性方面存在的局限性,提出了一种非下抽样抗混叠Contourlet变换(NS-NACT),其由非下抽样抗混叠塔式滤波器组(NS-NPFB)和非下抽样方向滤波器组(UDFB)构成。基于此,研究了一种基于自适应阈值调节的去噪算法。实验研究结果表明,当噪声方差σ=30时,通过本文算法去噪后的图像,不仅峰值信噪比(PSNR)较非抽样小波和Contourlet分别高出0.65dB和3.47dB,而且有效抑制了Contourlet变换去噪后的Gibbs现象,同时还可以更好地保留图像的边缘和细节,去噪效果更佳。 相似文献
18.
19.
模拟分析滤波器组的实现欠理想、系统噪声以及数字综合滤波器有效阶数实现所带来的系统误差均有可能造成混合滤波器组的设计出现解不稳定、无唯一解等病态问题,影响混合滤波器组的准确重构效果。本文首先给出了满足准确重构条件下,以综合滤波器组频域响应为求解变量的混合滤波器组线性求解模型。针对线性方程中系数矩阵以及目标向量受扰动误差影响特点,提出一种新的基于加权总体最小二乘正则化算法的IIR形式综合滤波器设计方法。算法以系统扰动误差最小化为目标函数,根据随机误差变量的二阶统计特性,采用加权总体最小二乘算法抑制滤波器实现误差以及随机噪声等扰动因素影响,使得到的综合滤波器组频域响应解的加权误差平方和最小化,并通过Tikhonov正则化方法优化病态情况下方程组解的稳定性。提出一种IIR类型的综合滤波器系数的求解算法,并利用正则化方法优化滤波器系数,提高系统稳定性。该方法可应用于过采样混合滤波器组的设计。仿真结果表明该算法的有效提高系统鲁棒性和改善重构性能。 相似文献
20.
针对可满足近似完全重构的双通道混合滤波器组,其中高阶数的模拟滤波器一般不容易设计优化。采用遗传算法设计5阶模拟分解滤波器,并基于逆快速傅里叶变换实现数字综合滤波器的设计优化以滤除掉镜像频谱,保证近似完全重构。文中设计了由5阶模拟分解滤波器和32阶数字综合滤波器组成的混合滤波器组,仿真结果表明:可以实现的最大失真误差为4.761 8×10-11dB,平均失真误差为-9.2×10-14dB,最大混叠误差为-154 dB,平均混叠误差为-200 dB,可满足24 bits的模数转换器系统的要求。 相似文献