基于四元数组稀疏的彩色图像去噪

Quaternion patch-group sparse coding for color image denoising

在采集和传播图像的过程中易受噪声的污染,从而降低了图像质量,对于后续的观察和处理产生较大影响。因此,图像去噪是当前图像处理领域一个重要的课题,其关键问题是如何在去除噪声的同时保留图像信息。由于图像具有自相似性,一般的图像去噪方法是利用组稀疏来重建图像。对于彩色图像提出了基于四元数组稀疏的去噪算法。首先,用四元数的形式来描述图像中的每个像素,从而构造出图像块组。在此基础上,该模型对每个图像块进行了更新,并用词字典中的线性组合对每个图像块组进行描述。为了进一步提高重构后的图像结构信息的准确性,结合了组稀疏模型和核维纳滤波器。核维纳滤波的基准影像是由组稀疏表达所获得的结果。与传统的方法比较,该模型既能将3种颜色通道的关联结合起来,又能使各图像块组间的关联性得到最大程度的发挥。实验表明,采用该方法重构的图像在不同的噪声等级下量化指标和视觉效果均有较好表现。

Images are inevitably corrupted by noise during transition and acquisition,which exerts a considerable influence on the subsequent processing.Therefore,image denoising is essential for image processing.Specially,the critical challenge of image denoising is to remove the noise while preserving information as much as possible.Generally,the group-based sparse representation model is exploited to restore the clean image,due to the self-similarity of natural images.This paper offered a novel color image denoising method that utilized quaternions in the group sparsity model,where each pixel was expressed as a pure quaternion.Initially,each pixel of the observed image was expressed as a quaternion unit,and a quaternion patch group matrix was established by Pearson′s correlation coefficient.The proposed model then learnt the dictionary for each patch group,working well with the pursuit algorithm.In other words,the group-based sparsity method assumed that each patch group was a linear combination of the basic elements of the dictionary.Unfortunately,it remained arduous to reconstruct the image structure precisely.Therefore,the group sparsity model incorporated kernel Wiener filtering to enhance image structure quality.In contrast to the traditional models,the new model not only worked with the corresponding RGB channels,but also leveraged the relationship between patches.Fueled by the exploration of the inner correlation of color channels,the proposed method could preserve the image information as much as possible while removing noise.The experiments validated the efficiency of the proposed method both in numerical results and visual performance on different noise levels.