Single-Frame Image Super-resolution through Contourlet Learning

We propose a learning-based, single-image super-resolution reconstruction technique using the contourlet transform, which is capable of capturing the smoothness along contours making use of directional decompositions. The contourlet coefficients at finer scales of the unknown high-resolution image are learned locally from a set of high-resolution training images, the inverse contourlet transform of which recovers the super-resolved image. In effect, we learn the high-resolution representation of an oriented edge primitive from the training data. Our experiments show that the proposed approach outperforms standard interpolation techniques as well as a standard (Cartesian) wavelet-based learning both visually and in terms of the PSNR values, especially for images with arbitrarily oriented edges.</p

Single frame image super-resolution: should we process locally or globally?

In this paper we study the usefulness of different local and global, learning-based, single-frame image super-resolution reconstruction techniques in handling three specific tasks, namely, de-blurring, de-noising and alias removal. We start with the global, iterative Papoulis-Gerchberg method for super-resolving a scene. Next we describe a PCA-based global method which faithfully reproduces a super-resolved image from a blurred and noisy low resolution input. We also study several multi-resolution processing schemes for super-resolution where the best edges are learned locally from an image database. We show that the PCA-based global method is efficient in handling blur and noise in the data. The local methods are adept in capturing the edges properly. However, both local and global approaches cannot properly handle the aliasing present in the low resolution observation. Hence we propose an alias removal technique by designing an alias-free upsampling scheme. Here the unknown high frequency components of the given partially aliased (low resolution) image is generated by minimizing the total variation of the interpolant subject to the constraint that part of alias free spectral components in the low resolution observation are known precisely and under the assumption of sparsity in the data

Single-frame image super-resolution using learned wavelet coefficients

We propose a single-frame, learning-based super-resolution restoration technique by using the wavelet domain to define a constraint on the solution. Wavelet coefficients at finer scales of the unknown high-resolution image are learned from a set of high-resolution training images and the learned image in the wavelet domain is used for further regularization while super-resolving the picture. We use an appropriate smoothness prior with discontinuity preservation in addition to the wavelet-based constraint to estimate the super-resolved image. The smoothness term ensures the spatial correlation among the pixels, whereas the learning term chooses the best edges from the training set. Because this amounts to extrapolating the high-frequency components, the proposed method does not suffer from oversmoothing effects. The results demonstrate the effectiveness of the proposed approach. (C) 2004

Super-resolution for simultaneous realization of resolution enhancement and motion blur removal based on adaptive prior settings

A super-resolution method for simultaneously realizing resolution enhancement and motion blur removal based on adaptive prior settings are presented in this article. In order to obtain high-resolution (HR) video sequences from motion-blurred low-resolution video sequences, both of the resolution enhancement and the motion blur removal have to be performed. However, if one is performed after the other, errors in the first process may cause performance deterioration of the subsequent process. Therefore, in the proposed method, a new problem, which simultaneously performs the resolution enhancement and the motion blur removal, is derived. Specifically, a maximum a posterior estimation problem which estimates original HR frames with motion blur kernels is introduced into our method. Furthermore, in order to obtain the posterior probability based on Bayes’ rule, a prior probability of the original HR frame, whose distribution can adaptively be set for each area, is newly defined. By adaptively setting the distribution of the prior probability, preservation of the sharpness in edge regions and suppression of the ringing artifacts in smooth regions are realized. Consequently, based on these novel approaches, the proposed method can perform successful reconstruction of the HR frames. Experimental results show impressive improvements of the proposed method over previously reported methods