【作者】 张钧芹；

【导师】 练秋生；

【作者基本信息】 燕山大学 ， 信号与信息处理， 2012， 硕士

【摘要】 超分辨率作为图像处理领域的一个重要分支，已经广泛应用于计算机视觉、医学图像处理、遥感图像处理、公共安全等领域，其主要解决的问题是从一幅或多幅低分辨率图像中重构高分辨率图像。由于稀疏表示在图像超分辨率中的广泛应用，本文构造两级字典及分频带字典处理单幅图像的超分辨率问题。首先，本文构造两级字典，恢复尽可能多的细节信息；同时利用图像的非局部自相似性，将其与迭代反向投影算法相结合，进行图像的后处理，进一步提高重构图像的质量。其次，除了利用两级字典恢复细节信息外，本文构造联合低频字典、中频字典以及高频字典的分频带字典，利用图像低频、中频、高频三者之间的预测关系，重新预测图像的中高频部分信息；同时利用非局部迭代反向投影算法进行图像的后处理。实验结果表明了算法的有效性。再次，传统基于学习的超分辨率算法存在图像的放大倍数由高低分辨率字典对决定的问题，为了克服以上不足，本文构造分频带字典，利用图像低中高三部分之间的预测关系重构图像。在假定插值图像与原始图像的低频信息基本相同的条件下，将中高频部分的稀疏表示作为限制约束条件，基于图像低中高频图像块稀疏表示相似性重构中高频图像块。同时将BM3D滤波与迭代反向投影算法相结合，进行图像的非局部处理。实验结果表明该算法在重构质量与速度方面达到一个更好的平衡。最后，构造多尺度分频带字典进行超分辨率重构，利用自适应的加权平均算法将不同尺度字典重构的图像进行融合得到高分辨率图像。实验结果表明提出的算法具有更高的重构质量及速度。更多还原

【Abstract】 As an active field in image processing, super-resolution has been widely appliedinto computer vision, medical imaging, image remote sensing and security detection,which aims to reconstruct high resolution image from one or multiple low resolutionimage(s). With the wide application of sparse representation in image super-resolution,two-stage and multi-frequency-band dictionaries are proposed for single imagesuper-resolution problem in this paper.Firstly, two-stage dictionaries are explored into recovering as much detailinformation as possible. Considering that there are many repetitive structures in naturalimage, nonlocal self-similarity information is combined properly with iterativeback-projection to post-process the image, i.e nonlocal iterative back-projection tofurther improve the reconstruction quality.Secondly, in addition to exploiting two-stage dictionaries to recover detailinformation, multi-frequency-band dictionaries consisting of low frequency (LF)dictionaries, middle frequency (MF) dictionaries and high frequency (HF) dictionariesare jointly learned to predict middle and high frequency information from low frequencycomponent by the prediction relation between LF\MF\HF components. Simultaneously,nonlocal iterative back-projection is applied into post-processing the image.Experimental results demonstrate the effectiveness of the proposed algorithm.Thirdly, the magnification factor of the traditional super-resolution algorithms onsparse representation is determined by high resolution\low resolution dictionary pairs. Toovercome the drawback, multi-frequency-band dictionaries are proposed forsuper-resolution problem only exploiting the prediction relation between LF\MF\HFcomponents to reconstruct the image. Considering the LF components consistency of theinterpolator image and original image, with the sparse representation of MF\HF patchesas the regularization condition, MF\HF patches are reconstructed exploiting thecoefficients similarity of LF\MF\HF patches. Furthermore, block matching and3D(BM3D) filtering is incorporated into iterative back-projection to postprocess the image nonlocally. Compared with other popular learning-based algorithms, the proposedmethod keeps better balance in reconstruction quality and speed.Finally, multiscale multiple-frequency-band dictionaries are constructed for SRproblem. The images reconstructed by dictionaries are fused by adaptive weightedaverage algorithm. Compared with other state-of-the-art algorithms, the proposed methodhas higher reconstruction quality and speed.更多还原