Abstract

Wavelet filtration algorithms are widely used for image processing; the majority of them are of threshold character: the wavelet decomposition coefficient whose value is smaller than some threshold value is equated to zero, otherwise, this coefficient is subjected to some (mostly nonlinear) transform which is defined by the used threshold function. When filtering contrast images, such treatment of decomposition coefficients may lead to the so-called artefacts in the filtered image — in the neighborhood of the stepwise change in the amplitude of the filtered image, the pulses appear that are absent in the initial image, which significantly worsens the filtration quality. To eliminate such artefacts, several approaches are considered in this study and a method is proposed whose gist consists in posttreatment of the result of wavelet filtration of images by means of nonlinear spatial filtering algorithms. The calculation experiment performed in this study has made it possible to come to the conclusion that the proposed method is efficient to eliminate the artefacts of wavelet filtration of contrast images.

中文翻译：

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图像的小波滤波伪像及其消除

摘要

小波滤波算法被广泛用于图像处理。它们中的大多数具有阈值特征：其值小于某个阈值的小波分解系数等于零，否则，该系数会经历一些（大多数是非线性的）变换，该变换由所使用的阈值函数定义。在对对比度图像进行滤波时，对分解系数的这种处理可能会在滤波后的图像中导致所谓的伪影-在滤波后的图像幅值的逐步变化附近，出现初始图像中不存在的脉冲，大大降低了过滤质量。为了消除此类伪影，在这项研究中考虑了几种方法，并提出了一种方法，其要点在于利用非线性空间滤波算法对图像的小波滤波结果进行后处理。在这项研究中进行的计算实验使得有可能得出结论，即该方法可有效消除对比度图像的小波滤波伪像。