用于图像恢复的基于SVR的自适应新滤波器的研究*

提出了一种用SVR回归器识别脉冲噪声的思想,并将其应用于图像滤波和恢复,形成了用于对脉冲噪声进行滤波的SVR自适应滤波器。这种滤波器在滤波时,先用SVR对待识别像素作噪声识别,再对含噪声的像素作中值滤波。用SVR作噪声识别时,先对滤波窗口作SVR回归,通过待识别像素回归距的大小判断其是否含有噪声。在进行SVR回归时,使用鲁棒的Huber损失函数。由于更充分地利用了待识别像素点的局部背景信息,这种滤波器提高了脉冲噪声识别的正确率。实验表明,在保留原图像的细节信息方面,其滤波效果要优于基于SVC的中值滤波器。     

Adaptive two-pass median filter based on support vector machines for image restoration

In this letter, a novel adaptive filter, the adaptive two-pass median (ATM) filter based on support vector machines (SVMs), is proposed to preserve more image details while effectively suppressing impulse noise for image restoration. The proposed filter is composed of a noise decision maker and two-pass median filters. Our new approach basically uses an SVM impulse detector to judge whether the input pixel is noise. If a pixel is detected as a corrupted pixel, the noise-free reduction median filter will be triggered to replace it. Otherwise, it remains unchanged. Then, to improve the quality of the restored image, a decision impulse filter is put to work in the second-pass filtering procedure. As for the noise suppressing both fixed-valued and random-valued impulses without degrading the quality of the fine details, the results of our extensive experiments demonstrate that the proposed filter outperforms earlier median-based filters in the literature. Our new filter also provides excellent robustness at various percentages of impulse noise.     

自适应中值滤波算法滤除医学图像脉冲噪声

实现了一种滤除医学图像脉冲噪声的自适应中值滤波算法,用均方根误差和噪声对原图像的毁坏程度两个客观评价指标对该算法及传统均值、中值滤波方法进行了比较与评价。根据设定条件检测滤波窗口中心像素是否为脉冲噪声,采取滤波窗口自适应的算法来滤除脉冲噪声,去除了传统中值滤波对所有像素均用中值代替的弊端,减少了不必要的图像细节损失。基于MATLAB的仿真实验表明,对于较大密度的脉冲噪声,该算法在有效抑制噪声的同时,能较好地保护边缘和细节信息。该算法已应用于虚拟内窥镜系统中,取得了令人满意的效果。     

Switching-based filter based on Dempster’s combination rule for image processing

In this work, a two-pass switching rank-ordered arithmetic mean (TSRAM) filter that preserves image details while effectively suppressing impulse noise is proposed to improve the performance of switching-based median filters. The proposed filter mechanism includes an efficient impulse detector based on the Dempster-Shafer (D-S) evidence theory and a rank-ordered arithmetic mean filter that works by estimating the noise-free ordered mean values excluding the current pixel. A modified Dempster’s combination rule is applied to the impulse detector. To improve filtering performance, a simple switching median filter is included to perform second-pass filtering. Experimental results show that the proposed filter outperforms many well-accepted switching-based median filters in terms of both noise suppression and detail preservation, providing excellent robustness at various percentages of impulse noise.     

基于模糊推理的多窗口中央值滤波器设计方法

提出了一种基于模糊推理用于去除图像椒盐噪声的中央值滤波器的新型设计方法,在图像复原处理中,理想的期望是对图像被劣化的部分处理,没有被劣化的部分不作处理,但实际图像处理中处理点是否为噪声点具有模糊性.利用模糊推理对处理点像素多大程度上属于劣质像素进行推定,并且多个模糊滤波器联合使用,处理结果证明对广范围噪声发生率的各种被椒盐噪声劣化的图像复原处理都适用.     

The solutions of equation-based noise detector for an adaptive median filter

Techniques of noise detection have been widely applied in impulse noise reduction. However, the phenomenon of pixel misclassification is very obvious in high noise density. In order to improve pixel identification, in this paper, the new noise detector is proposed. Based on solutions of equations, an estimated block of every 8×8 block of a noise image is generated. Then, according to relationships between these noise blocks and their estimated blocks, corrupted and uncorrupted pixels are identified. During image filtering, a noise-detection-based adaptive median algorithm is presented. Experimental results show that the proposed filter can well reduce the impulse noise and preserve more details of original images.     

基于图像受噪程度的改进模糊加权均值滤波

根据高斯噪声密度大、噪声强度的波动范围宽,其污染图像不仅每一个像素灰度级都会受影响,而且即使是同一灰度级受污染的程度也会不同的特点和传统的图像模糊滤波算法在图像细节保护方面上的不足,提出基于图像受噪程度的改进模糊加权均值滤波算法,该算法根据图像各像素点的受噪程度,得到首次滤波图像和原图像估计直方图,根据该直方图确定模糊隶属度函数,然后对首次滤波图像中灰度小于25的像素点进行模糊加权均值滤波,该算法在不需要期望图像和高斯噪声方差的情况下能有效地去除噪声,同时能够很好地保护图像细节信息。     

考虑均值的滤除脉冲噪声的自适应非线性滤波

针对脉冲噪声滤除,提出一种基于均值的自适应非线性滤波。其算法思想是先进行噪声检测并生成相应的噪声标志矩阵,随后扫描噪声标志矩阵,对信号点则直接输出,而噪声点则根据窗口内噪声点个数自适应选择滤波窗口,接着生成一个由滤波窗口各像素灰度与相应均值之差形成的差别矩阵,并赋予差别矩阵各元素不同的权重,最后返回加权后差别矩阵中最小值的位置,并用该像素的灰度取代噪声点。噪声点滤除算法,其实质是找出一个空间位置上离噪声点最近且最接近均值的像素的灰度来取代噪声点。通过实验,该方法具有更好的综合滤波性能。     

一种改进的自适应中值滤波方法

提出了一种改进的自适应中值滤波算法,以有效地去除图像中的脉冲噪声,并保留图像细节。在进行噪声点检测时,引入了最小集合距离测度,有效地避免了将高频细节信号误判为噪声。采用最小无污染点集合的中值恢复噪声点,消除了其邻域噪声点的影响。通过与RAMF、NASMF等方法的比较实验表明,新算法噪声检测的正确率高、降噪与保留细节效果好, 尤其对含噪声密度高的图像的处理效果优势更为明显。     

基于差分分层噪声检测的开关中值滤波算法

为了精确地检测出图像中的脉冲噪声并滤除,提出了一种差分分层噪声检测的开关中值滤波算法。该算法对噪声检测窗口内像素点按灰度值大小排序,通过差分方法划分出高、低阶噪声块和信号块3部分。当待测像素点属于信号块时视其为信号点;否则,视其为可能噪声点。利用可能噪声点与信号块中与其灰度值最临近的信号点的灰度的差定义了梯度函数,在梯度函数的基础上定义了用于对可能噪声点进行二次检测的模糊隶属函数,对滤波方法进行模糊加权,得到一种加权滤波方法。实验结果证明了该算法对脉冲噪声有很强的抑制作用。     

基于中值的自适应均值滤波算法

中值滤波和均值滤波通常被分别用来处理脉冲噪声和高斯噪声.但是当图像同时存在高斯噪声和脉冲噪声时,单独用那种滤波方法都不会达到最好的去噪效果.针对该问题,提出了一种基于中值的改进自适应加权均值滤波算法.该算法采用了一种基于自适应阈值的方法对滤波系数加以优化,使其可以更有效地减少噪声,又可以较好的保持图像的边缘细节信息.实验结果表明,该算法能较好的滤除混合噪声,且滤波效果优于传统的滤波算法.     

一种新的基于噪声点检测的脉冲噪声去噪算法

中值滤波是广泛应用于去除脉冲噪声的一种非线性去噪方法,但是单一地使用中值滤波方法去除脉冲噪声会造成图像细节信息的丢失,从而使图像变得模糊。基于噪声点检测的脉冲噪声滤波方法可以在滤除噪声的同时有效地保持图像的细节信息。该文在此基础上提出了一种新的基于噪声点检测的脉冲噪声滤波算法,该算法在检测噪声点时用被检测点的中值滤波结果作为判定该点是否为噪声点的依据。而在滤除被检测到的噪声点时,采用的是迭代的中值滤波算法。从实验结果中可以看到,与其它中值滤波算法相比,该文的算法在去除脉冲噪声时能取得较好的效果。     

Image enhancement using deep-learning fully connected neural network mean filter

Improving the quality of a noisy image is important for image applications. Many novel schemes pay great efforts in the removal of impulse noise. Most of them restore noisy pixels only by using the neighboring noise-free pixels, but the relationship between a noisy image and its noise-free one, which denotes the clean image not corrupted by noise, is ignored. So the reconstruction quality cannot be further improved. In this study, we employ a deep-learning fully connected neural network (FCNN) to select top N candidates of neighboring un-corrupted pixels for the restoration of a center noisy pixel in an analysis window. Hence, the mean value of the gray levels of these top N pixels is computed and employed to replace the noisy pixel, yielding the noisy pixel being restored. The experimental results reveal that the proposed deep-learning FCNN mean filter can remove impulse noise effectively in corrupted images with different noise densities.

     

基于模糊神经网络的脉冲噪声滤波器

针对一般模糊神经网络结构复杂、不利于硬件实现的问题,提出了一种基于Sugeno型模糊神经网络的新型脉冲噪声滤波器,该滤波器采用神经网络的结构设计,有利于噪声模式的检测,其内含于神经网络中的模糊推理机制不仅能够有效地滤除脉冲噪声,而且又不破坏图象的细节,该滤波器还采用能够获得全局解的遗传算法来对网络进行调整,初步研究表明,该模糊神经滤波器在滤除景物图象中的脉冲噪声方面,优于标准中值滤波器。     

一种基于偏导数的滤波算法

提出了一种新的图像噪声消除算法。该方法可以快速有效地去除图像中的脉冲噪声,并保留图像的细节。该算法主要利用像素点的偏导数信息把所有的像素点分为有效的信号点和噪声点,判定的标准为:任意像素点的值如果在其邻域为最大或最小值,则认为该点是噪声点,否则就是有效点。实验结果表明,本算法去除噪声与保留细节的效果好,且运算速度较快。     

一种新的基于PCNN的图像脉冲噪声滤波算法

为了更好地滤除图像中的脉冲噪声,在分析脉冲耦合神经网络(PCNN)的工作机理的基础上,在PCNN中引入了点火映射图的概念,并提出了一种新的基于PCNN点火映射图的图像脉冲噪声滤波器。该方法首先通过运行PCNN把噪声图像转化为点火映射图,然后利用点火映射图对图像中的脉冲噪声进行定位,最后仅对定位的噪声进行自适应滤波。计算机仿真实验表明,该方法的去噪效果优于传统方法,从而验证了该方法的有效性、合理性。     

相似邻居数目图像脉冲噪声滤波算法

为了去除图像随机脉冲噪声的同时保留边缘,提出一种新方法。该方法首先利用图像局部灰度相似性来构造相似邻居数目图,一个像素的相似邻居数目在窗口内最大或数值较大,才可能认为是没有受到噪声干扰的像素。根据噪声密度不同采用不同方法检测。实验结果表明,阈值能适应性不同图像类型,滤波结果优于大部分已有算法,且算法复杂度低于大部分改进的中值滤波算法。     

基于四分法噪声检测的开关中值滤波算法

为了精确的检测出图像中的脉冲噪声并滤除,提出一种差分四分法的开关中值滤波算法.该算法对噪声检测窗口内像素按灰度值大小排序,通过差分方法划分出高、低阶信号块和高,低阶噪声块4部分.当待测像素属于高,低阶信号块时视其为信号点,否则,根据噪声块与信号块内像素比例关系确定其为噪声点或可能噪声点,若为可能噪声点,则扩展检测窗口重新检测.对于噪声点,基于其邻域噪声密度自适应的确定滤波窗口,取滤窗内信号点的中值作为滤波输出.实验证明该算法对脉冲噪声有很强的抑制作用.     

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.     

一种改进的极值均值自适应滤波算法

为了在滤除噪声的同时保持图像细节,提出了一种新型自适应滤波算法。该算法根据图像中的某点是否为邻域极值点,将全部像素分为可疑噪声和信号两类,若中心点属于可疑噪声,将其并入信号类组成一新类,并计算其均值与信号类均值的差值,再通过与阈值比较,确定是否用信号类的中值取代原噪声图像的值。滤波窗口能根据噪声密度自适应改变大小。实验表明,该算法具有良好的滤波性能,尤其在噪声严重时,效果优于其他中值滤波算法。