基于非局部自相似的Shearlet自适应收缩图像去噪

针对Shearlet收缩去噪引入的Gibbs伪影和"裂痕"现象,提出一种结合非局部自相似的Shearlet自适应收缩图像去噪方法.首先,对噪声图像进行多方向多尺度的Shearlet分解;然后,基于高斯比例混合(GSM)模型的Shearlet系数分布建模,利用贝叶斯最小二乘估计对Shearlet系数进行自适应收缩去噪,重构得到初始去噪图像;最后,利用非局域自相似模型对初始去噪图像进行滤波处理,得到最终的去噪图像.实验结果表明,所提方法在更好地保留边缘特征的同时,有效地去除噪声和收缩去噪引入的Gibbs伪影,该方法获得的峰值信噪比(PSNR)和结构自相似指标(SSIM)比基于非抽样剪切波变换(NSST)的硬阈值去噪方法提高1.41 dB和0.08;比非抽样Shearlet域GSM模型去噪方法提高1.04 dB和0.045;比基于三变量模型的剪切波去噪方法提高0.64 dB和0.025.     

Quantum and impulse noise filtering from breast mammogram images

Recent advances in the field of image processing have shown that level of noise highly affect the quality and accuracy of classification when working with mammographic images. In this paper, we have proposed a method that consists of two major modules: noise detection and noise filtering. For detection purpose, neural network is used which effectively detect the noise from highly corrupted images. Pixel values of the window and some other features are used as feature for the training of neural network. For noise removal, three filters are used. The weighted average value of these three filters is filled on noisy pixels. The proposed technique has been tested on salt & pepper and quantum noise present in mammogram images. Peak signal to noise ratio (PSNR) and structural similarity index measure (SSIM) are used for comparison of proposed technique with different existing techniques. Experiments shows that proposed technique produce better results as compare to existing methods.     

Non-blind digital watermarking with enhanced image embedding capacity using DMeyer wavelet decomposition,SVD, and DFT

Amongst the requirements of digital color image watermarking–capacity is the major component to be addressed effectively. To address the same we proposed a method for inserting a color image into another color image of same size using non-blind watermarking scheme. From this method we achieved reasonably good perceptual similarity by measuring acceptable peak signal to noise ratio (PSNR) and structural similarity (SSIM) index. The method uses DMeyer single level discrete wavelet transformation (DWT) to get approximation coefficients-where most of the image information is stored, discrete Fourier transformation (DFT) is used to get set of components which are sufficient to describe the whole image and singular value decomposition (SVD) to get reliable orthogonal matrix of computationally sustainable components of the transformed image. The method is robust against attacks like–rotation, cropping, JPEG compression and for noises–salt and pepper, gaussian, speckle.     

一种基于中值滤波的图像去噪算法

由于图像噪声会对后续的图像处理结果产生影响,所以在对图像进行其他处理前应先对图像去噪。针对传统中值滤波器在去除均匀分布椒盐噪声时效果并不理想,设计出一种自适应阈值中值滤波器。分别用两种滤波器进行图像去噪实验,通过对比去噪后图像的信噪比、峰值信噪比以及视觉效果发现:较之传统的中值滤波器,新的自适应中值滤波器能更有效地去除椒盐噪声并减少图像失真。     

A hybrid denoising algorithm based on shearlet transform method and Yaroslavsky’s filter

In this paper, we have proposed a hybrid denoising algorithm based on combining of the shearlet transform method, as a pre-processing step, with the Yaroslavsky’s filter, as a kernel smoother, on a wide class of images with various properties such as thin features and textures. In the other word, proposed algorithm is a two-step algorithm, where in the first step the image is filtered by shearlet transform method and in the second step the weighted Yaroslavsky’s filter is applied on result of first step. The weight coefficients of the Yaroslavsky’s filter are achieved by pixel similarities in the denoised image from the first step. The theoretical results are confirmed via simulations for 2D images corrupted by additive white Gaussian noise. Experimental results illustrate that proposed hybrid method has good effect on suppressing the pseudo-Gibbs and shearlet-like artifacts can obtain better performance in terms of mean square error (MSE), peak signal to noise ratio (PSNR) and structural similarity (SSIM) index rather than existing state-of-the-art methods.     

Determination of optimal parameters for bilateral filter in brain MR image denoising

Noise elimination is an important pre-processing step in magnetic resonance (MR) images for clinical purposes. In the present study, as an edge-preserving method, bilateral filter (BF) was used for Rician noise removal in MR images. The choice of BF parameters affects the performance of denoising. Therefore, as a novel approach, the parameters of BF were optimized using genetic algorithm (GA). First, the Rician noise with different variances (σ = 10, 20, 30) was added to simulated T1-weighted brain MR images. To find the optimum filter parameters, GA was applied to the noisy images in searching regions of window size [3 × 3, 5 × 5, 7 × 7, 11 × 11, and 21 × 21], spatial sigma [0.1–10] and intensity sigma [1–60]. The peak signal-to-noise ratio (PSNR) was adjusted as fitness value for optimization.After determination of optimal parameters, we investigated the results of proposed BF parameters with both the simulated and clinical MR images. In order to understand the importance of parameter selection in BF, we compared the results of denoising with proposed parameters and other previously used BFs using the quality metrics such as mean squared error (MSE), PSNR, signal-to-noise ratio (SNR) and structural similarity index metric (SSIM). The quality of the denoised images with the proposed parameters was validated using both visual inspection and quantitative metrics. The experimental results showed that the BF with parameters proposed by us showed a better performance than BF with other previously proposed parameters in both the preservation of edges and removal of different level of Rician noise from MR images. It can be concluded that the performance of BF for denoising is highly dependent on optimal parameter selection.     

灰度极限脉冲耦合神经网络混合噪声滤波

针对图像中同时存在椒盐噪声和高斯噪声,提出一种基于灰度极限和脉冲耦合神经网络(PCNN)滤除混合噪声的新方法。首先,根据灰度极值定位出椒盐噪声点;其次,在滤波窗口中对椒盐噪声点进行均值滤波;然后,利用PCNN赋时矩阵定位出高斯噪声点;最后,自适应调整可变灰度步长,选择不同滤波方法滤除高斯噪声。实验结果表明提出的算法较常见的混合噪声滤波方法在主观滤波效果和客观评价指标峰值信噪比(PSNR)及信噪比改善因子(ISNR)两方面均有明显的优势。     

一种新的线性混合滤波器

提出一种新的滤波器,称为线性混合滤波器（简称为LMF）,它适用于恢复被一类混合噪音（即一致脉冲噪音与高斯噪音）污染的数字图像。当混合噪音强度在一定范围内变化时,它具有自动调节机制。与若干已知的同类滤波器相比,LMF的速度更快,具有简单而统一的控制参数计算公式,而不是关于参数的选取范围。而且从实验结果可见,用LMF时峰值信噪比得到提高,均方误差得到降低。     

基于POCS算法的图像超分辨率重建

传统POCS算法对图像进行超分辨率重建时,一般都假设所处理的噪声为零均值的加性高斯白噪声,当噪声为非高斯噪声如椒盐噪声时,POCS算法的重建效果将会下降.针对这一问题,本文对含噪图像首先采用平稳离散小波变换技术进行去噪预处理,然后再用POCS算法重建图像.实验证明,此方法对信噪比较低的图像有很好的重建效果,对高斯及椒盐等噪声处理比较有效.     

改进的曲率滤波强噪声图像去噪方法

目的 医学影像获取和视频监控过程中会出现一些恶劣环境,导致图像有许多强噪声斑点,质量较差。在处理强噪声图像时,传统的基于变分模型的算法,因需要计算高阶偏微分方程,计算复杂且收敛较慢;而隐式使用图像曲率信息的曲率滤波模型,在处理强噪声图像时,又存在去噪不完全的缺陷。为了克服这些缺陷,在保持图像边缘和细节特征的同时去除图像的强噪声,实现快速去噪,提出了一种改进的曲率滤波算法。方法 本文算法在隐式计算曲率时,通过半窗三角切平面和最小三角切平面的组合,用投影算子代替传统曲率滤波的最小三角切平面投影算子,并根据强噪声图像存在强噪声斑点的特征,修正正则能量函数,增添局部方差的正则能量,使得正则项的约束更加合理,提高了算法的去噪性能,从而达到增强去噪能力和保护图像边缘与细节的目的。结果 针对多种不同强度的混合噪声图像对本文算法性能进行测试,并与传统的基于变分法的去噪算法（ROF）和曲率滤波去噪等算法进行去噪效果对比,同时使用峰值信噪比（PSNR）和结构相似性（SSIM）作为滤波算法性能的客观评价指标。本文算法在对强噪声图像去噪处理时,能够有效地保持图像的边缘和细节特征,具备较好的PSNR和SSIM,在PSNR上比ROF模型和曲率滤波算法分别平均提高1.67 dB和2.93 dB,SSIM分别平均提高0.29和0.26。由于采用了隐式计算图像曲率,算法的处理速度与曲率滤波算法相近。结论 根据强噪声图像噪声特征对曲率滤波算法进行优化,改进投影算子和能量函数正则项,使得曲率滤波算法能够更好地适用于强噪声图像,实验结果表明,该方法与传统的变分法相比,对强噪声图像去噪效果显著。     

An automatic filtering convergence method for iterative impulse noise filters based on PSNR checking and filtered pixels detection

Whether input images are corrupted by impulse noise and what the noise density level is are unknown a priori, and thus published iterative impulse noise filters cannot adaptively reduce noise, resulting in a smoothing image or unclear de-noising. For this reason, this paper proposes an automatic filtering convergence method using PSNR checking and filtered pixel detection for iterative impulse noise filters. (1) First, the similarity between the input image and the 1st filtered image is determined by calculating MSE. If MSE is equal to 0, then the input image is unfiltered and becomes the output. (2) Otherwise, one applies PSNR checking and filtered pixel detection to estimate the difference between the tth filtered image and the t–1th filtered image. (3) Finally, an adaptive and reasonable threshold is defined to make the iterative impulse noise filters stop automatically for most image details preservation in finite steps. Experimental results show that iterative impulse noise filters with the proposed automatic filtering convergence method can remove much of the impulse noise and effectively maintain image details. In addition, iterative impulse noise filters operate more efficiently.     

基于ROLD统计量的混合噪音线性滤波算法

提出一种基于ROLD统计量的混合噪音线性滤波算法（RLMF）。算法把用来检测脉冲噪音的ROLD统计量运用于混合噪音的滤波算法上,提高了混合噪音中脉冲噪音成分的检测效率,它不仅适用于恢复被混合噪音污染的数字图像,而且也适用于恢复被纯脉冲噪音或纯高斯噪音污染的数字图像。仿真实验证明,RLMF滤波后的图像视觉效果和PSNR均优于已知的同类滤波器。     

结合修剪均值与高斯加权中值滤波的图像去噪算法

为快速准确地滤除图像中的脉冲噪声并较好地保持图像的纹理细节和边缘结构,提出一种基于修剪均值与高斯加权中值滤波的图像去噪算法。根据脉冲噪声的灰度特征与统计特征,以局部统计方式进行噪声检测,将灰度取最小值或最大值且与邻域像素相关性较小的像素识别为噪声像素。对于图像平滑区域和细节区域中的噪声像素,使用自适应修剪均值和高斯加权中值滤波算法进行去噪处理。实验结果表明,该算法在视觉效果、峰值信噪比、结构相似性及计算速度上均优于对比算法,并且能够在彻底滤除噪声的同时,较好地保持图像的纹理细节和边缘结构。     

自适应残差图像的分数阶全变分去噪算法

目的 全变分（TV）去噪模型具有较好的去噪效果,但对于图像的弱边缘和纹理细节的保持不够理想。自适应分数阶全变分（AFTV）模型根据图像局部信息,区分图像的纹理区域和非纹理区域,自适应计算投影算法中的软阈值,可较好地保持图像的弱边缘和纹理细节,但该方法当噪声增大时“阶梯”效应比较明显,弱边缘和纹理细节保持效果不够理想。针对该问题,提出一种改进的分数阶全变分去噪算法。方法 该算法在计算残差图像时,用分数阶全变分模型替代整数一阶全变分模型,并根据较精确的残差图像的局部方差区分图像纹理区域和平坦区域,使保真项参数的自适应选取更加合理,提高了算法的去噪性能。结果 针对3种不同类型的噪声图像,将本文模型与TV模型和AFTV模型进行对比实验,并采用峰值信噪比（PSNR）和结构相似性（SSIM）评定去噪效果和纹理保持能力。对于高斯噪声图像,本文算法在PSNR方面比TV模型和AFTV模型分别可平均提高2.72 dB和1.38 dB,SSIM分别可平均提高0.047和0.020。对于椒盐噪声图像,本文算法结合中值滤波算法在PSNR和SSIM方面比传统中值滤波算法分别可平均提高1.308 dB和0.011。对于泊松噪声图像,本文算法在PSNR、SSIM方面与AFTV较接近,比TV分别可提高1.59 dB和0.005。结论 通过对添加不同类型的噪声图像进行实验,结果表明提出的算法在去噪性能上与TV和AFTV相比均有较大提高,尤其对于噪声较大的图像效果更为显著,在去噪效率上与AFTV的时间复杂度相当,时耗接近略有降低。且本文算法普适性较好,能有效去除多种典型类型的噪声。     

Fuzzy based Impulse Noise Reduction Method

In this paper, we propose an image filtering technique based on fuzzy logic control to remove impulse noise for low as well as highly corrupted images. The proposed method is based on noise detection, noise removal and edge preservation modules. The main advantage of the proposed technique over the other filtering techniques is its superior noise removal as well as detail preserving capability. Based on the criteria of peak-signal-to-noise-ratio (PSNR), mean square error (MSE), structural similarity index measure (SSIM) and subjective evaluation measure we have found experimentally that the proposed method provides much better performance than the state-of-the-art filters. To analyze the detail preservation capability of the proposed filter sensitivity analysis is performed by changing the detail preservation module to see its effects on the details (texture and edge information) of resultant image. This sensitivity analysis proves experimentally that significant image details have been preserved by the proposed method.     

基于多参数小波阈值函数的图像去噪

针对图像中的强高斯噪声提出了一种新的小波阈值降噪函数。传统的软阈值法对图像去噪有明显的效果,但对强高斯噪声效果不甚理想,于是构造出一种新的小波阈值函数,此函数包含阈值[λ],调节因子[t]和[n]三个参数,能够自适应地调节阈值的变化。实验以噪声图像与去噪后图像之间的峰值信噪比（PSNR）最大化为准则,采用PSO粒子群算法优化阈值函数中参数[n]和[t]的选取。仿真实验结果表明该方法不仅可以有效地去除噪声,又能避免有用高频信息的损失,提高了图像的信噪比;尤其在强高斯噪声下,相对软阈值法PSNR可提高6~7 dB,表明了此改进阈值法对于强高斯噪声图像降噪的有效性。     

一种基于 MAD 的鲁棒性分形维数计算方法及图像识别应用

传统鲁棒差分盒计数法（ RDBC）已成功用于高斯噪声图像的分形维估计,但由于对椒盐噪声较敏感,因此不再适用于椒盐噪声图像的分形维估计和图像分类。本文提出一种基于中值绝对偏差（MAD）的分形维数计算方法（MAD-DBC）。该方法利用MAD进行差分盒计数,对椒盐噪声具有很好的鲁棒性特点。实验结果表明,利用小波多分辨率的DBC、RD-BC和MAD-DBC对椒盐噪声的16种Brodatz纹理图像进行分类,MAD-DBC具有更高的识别率和更好的噪声鲁棒性。     

一种基于模糊神经系统的图像去噪方法

提出一种对含有高斯噪声的数字图像的去噪方法,这种方法能够增强高斯噪声滤波器的性能,减少去噪对图像造成的模糊和失真。设计了一个模糊推理系统（FIS）,并利用ANFIS训练这个FIS。通过训练可以调整、优化FIS的内部参数值。训练图像数据由计算机程序自动生成。优化后的FIS即可处理输入的图像数据,产生增强的图像。从结果图像的视觉效果和量化标准两方面的实验和分析,可以看出这种方法可基本消除高斯噪声滤波器产生的模糊和失真,提高滤波器性能。实验表明模糊神经系统可以应用于图像去噪问题。在合理地选择隶属度函数、规则和训练数据的前提下,会产生明显的图像增强效果。     

基于改进BM3D算法的椒盐噪声去噪

在处理由椒盐噪声污染的高对比度图像时,使用传统的三维块匹配算法（Block-Matching and 3D filtering,BM3D）去噪不能有效保留图像的边缘和纹理细节,在图像的边缘会出现边缘振铃效应。为了改善传统BM3D算法在处理椒盐噪声时的不足,提出了用边缘方向代替水平方向搜索相似块的BM3D改进去噪算法。实验结果表明,改进BM3D算法获得的相似块数量是传统BM3D算法的3倍,峰值信噪比（PSNR）也得到进一步提高,在去除椒盐噪声的同时也使图像边缘得到有效保留。     

图像椒盐噪声的自适应滤波算法研究

为有效去除严重的椒盐噪声、更好地保护图像细节,提出了一种基于改进脉冲耦合神经网络（PCNN）的自适应去噪方法。根据PCNN神经网络的点火时刻矩阵,对受噪声污染的像素进行定位,仅对噪声像素进行类中值滤波,实现了图像细节的有效保留;根据噪声强度的估计信息,自动进行滤波次数和滤波窗口尺寸的优选,实现了图像的强自适应滤波。实验表明,与传统去噪方法相比,该方法噪声去除效果好,图像细节保持完整,而且系统具有一定的泛化能力。