Results 1 - 10 of 86

Fundamental Limits of Reconstruction-Based superresolution algorithms . . .

by Zhouchen Lin, Heung-yeung Shum , 2004
"... Superresolution is a technique that can produce images of a higher resolution than that of the originally captured ones. Nevertheless, improvement in resolution using such a technique is very limited in practice. This makes it significant to study the problem: “Do fundamental limits exist for super ..."
Abstract - Cited by 107 (7 self) - Add to MetaCart
Superresolution is a technique that can produce images of a higher resolution than that of the originally captured ones. Nevertheless, improvement in resolution using such a technique is very limited in practice. This makes it significant to study the problem: “Do fundamental limits exist for superresolution?” In this paper, we focus on a major class of superresolution algorithms, called the reconstruction-based algorithms, which compute high-resolution images by simulating the image formation process. Assuming local translation among low-resolution images, this paper is the first attempt to determine the explicit limits of reconstruction-based algorithms, under both real and synthetic conditions. Based on the perturbation theory of linear systems, we obtain the superresolution limits from the conditioning analysis of the coefficient matrix. Moreover, we determine the number of low-resolution images that are sufficient to achieve the limit. Both real and synthetic experiments are carried out to verify our analysis.

A Frequency Domain Approach to Registration of Aliased Images with Application to Super-resolution

by Patrick Vandewalle, Sabine Süsstrunk, Martin Vetterli , 2006
"... Super-resolution algorithms reconstruct a high-resolution image from a set of low-resolution images of a scene. Precise alignment of the input images is an essential part of such algorithms. If the low-resolution images are undersampled and have aliasing artifacts, the performance of standard regist ..."
Abstract - Cited by 104 (9 self) - Add to MetaCart
Super-resolution algorithms reconstruct a high-resolution image from a set of low-resolution images of a scene. Precise alignment of the input images is an essential part of such algorithms. If the low-resolution images are undersampled and have aliasing artifacts, the performance of standard registration algorithms decreases. We propose a frequency domain technique to precisely register a set of aliased images, based on their low-frequency, aliasing-free part. A high-resolution image is then reconstructed using cubic interpolation. Our algorithm is compared to other algorithms in simulations and practical experiments using real aliased images. Both show very good visual results and prove the attractivity of our approach in the case of aliased input images. A possible application is to digital cameras where a set of rapidly acquired images can be used to recover a higher-resolution final image.

Space-time super-resolution

by Eli Shechtman, Yaron Caspi, Michal Irani - PAMI , 2005
"... We propose a method for constructing a video sequence of high space-time resolution by combining information from multiple low-resolution video sequences of the same dynamic scene. Super-resolution is performed simultaneously in time and in space. By “temporal super-resolution” we mean recoverin ..."
Abstract - Cited by 65 (2 self) - Add to MetaCart
We propose a method for constructing a video sequence of high space-time resolution by combining information from multiple low-resolution video sequences of the same dynamic scene. Super-resolution is performed simultaneously in time and in space. By “temporal super-resolution” we mean recovering rapid dynamic events that occur faster than regular frame-rate. Such dynamic events are not visible (or else observed incorrectly) in any of the input sequences, even if these are played in “slow-motion”. The spatial and temporal dimensions are very different in nature, yet are interrelated. This leads to interesting visual tradeoffs in time and space, and to new video applications. These include: (i) treatment of spatial artifacts (e.g., motionblur) by increasing the temporal resolution, and (ii) combination of input sequences of different space-time resolutions (e.g., NTSC, PAL, and even high quality still images) to generate a high quality video sequence. We further analyze and compare characteristics of temporal super-resolution to those of spatial super-resolution. These include: How many video cameras are needed to obtain increased resolution? What is the upper bound on resolution improvement via super-resolution? What is the optimal camera configuration for various scenarios? What is the temporal analogue to the spatial “ringing” effect?

Increasing space-time resolution in video

by Eli Shechtman, Yaron Caspi, Michal Irani - In ECCV , 2002
"... Abstract. We propose a method for constructing a video sequence of high space-time resolution by combining information from multiple lowresolution video sequences of the same dynamic scene. Super-resolution is performed simultaneously in time and in space. By “temporal super-resolution ” we mean rec ..."
Abstract - Cited by 44 (1 self) - Add to MetaCart
Abstract. We propose a method for constructing a video sequence of high space-time resolution by combining information from multiple lowresolution video sequences of the same dynamic scene. Super-resolution is performed simultaneously in time and in space. By “temporal super-resolution ” we mean recovering rapid dynamic events that occur faster than regular frame-rate. Such dynamic events are not visible (or else observed incorrectly) in any of the input sequences, even if these are played in “slow-motion”. The spatial and temporal dimensions are very different in nature, yet are inter-related. This leads to interesting visual tradeoffs in time and space, and to new video applications. These include: (i) treatment of spatial artifacts (e.g., motion-blur) by increasing the temporal resolution, and (ii) combination of input sequences of different space-time resolutions (e.g., NTSC, PAL, and even high quality still images) to generate a high quality video sequence. Keywords. Super-resolution, space-time analysis. 1
(Show Context)

Parameter Estimation in Bayesian High-Resolution Image Reconstruction With Multisensors

by Rafael Molina, Miguel Vega, Javier Abad, Aggelos K. Katsaggelos - IEEE Transactions on Image Processing , 2003
"... In this paper, we consider the estimation of the unknown parameters for the problem of reconstructing a high-resolution image from multiple undersampled, shifted, degraded frames with subpixel displacement errors. We derive mathematical expressions for the iterative calculation of the maximum likeli ..."
Abstract - Cited by 37 (10 self) - Add to MetaCart
In this paper, we consider the estimation of the unknown parameters for the problem of reconstructing a high-resolution image from multiple undersampled, shifted, degraded frames with subpixel displacement errors. We derive mathematical expressions for the iterative calculation of the maximum likelihood estimate of the unknown parameters given the low resolution observed images. These iterative procedures require the manipulation of block-semi circulant (BSC) matrices, that is block matrices with circulant blocks. We show how these BSC matrices can be easily manipulated in order to calculate the unknown parameters. Finally the proposed method is tested on real and synthetic images. Index Terms---Bayesian methods, high-resolution image reconstruction, parameter estimation.
(Show Context)

Super Resolution of Images and Video

by Aggelos K. Katsaggelos, Rafael Molina, Javier Mateos
"... ..."
Abstract - Cited by 32 (10 self) - Add to MetaCart
Abstract not found

High-Resolution Images from Low-Resolution Compressed Video

by C. Andrew Segall, Rafael Molina, Aggelos K. Katsaggelos - IEEE Signal Processing Magazine , 2003
"... this article, we utilize the terms SR, HR, and resolution enhancement interchangeably. ) For example, literature reviews are presented in [1] and [2] as well as this special section. Work traditionally addresses the resolution enhancement of frames that are filtered and down-sampled during acquisiti ..."
Abstract - Cited by 28 (9 self) - Add to MetaCart
this article, we utilize the terms SR, HR, and resolution enhancement interchangeably. ) For example, literature reviews are presented in [1] and [2] as well as this special section. Work traditionally addresses the resolution enhancement of frames that are filtered and down-sampled during acquisition and corrupted by additive noise during transmission and storage. In this article, though, we review approaches for the SR of compressed video. Hybrid motion compensation and transform coding methods are the focus, which incorporates the family of ITU and MPEG coding standards [3], [4]. The JPEG still image coding systems are also a special case of the approach
(Show Context)

Super-Resolution From Unregistered and Totally Aliased Signals Using Subspace Methods

by Patrick Vandewalle, Luciano Sbaiz, Joos Vandewalle, Martin Vetterli , 2007
"... In many applications, the sampling frequency is limited by the physical characteristics of the components: the pixel pitch, the rate of the analog-to-digital (A/D) converter, etc. A lowpass filter is usually applied before the sampling operation to avoid aliasing. However, when multiple copies are ..."
Abstract - Cited by 28 (8 self) - Add to MetaCart
In many applications, the sampling frequency is limited by the physical characteristics of the components: the pixel pitch, the rate of the analog-to-digital (A/D) converter, etc. A lowpass filter is usually applied before the sampling operation to avoid aliasing. However, when multiple copies are available, it is possible to use the information that is inherently present in the aliasing to reconstruct a higher resolution signal. If the different copies have unknown relative offsets, this is a nonlinear problem in the offsets and the signal coefficients. They are not easily separable in the set of equations describing the super-resolution problem. Thus, we perform joint registration and reconstruction from multiple unregistered sets of samples. We give a mathematical formulation for the problem when there are sets of samples of a signal that is described by expansion coefficients. We prove that the solution of the registration and reconstruction problem is generically unique

A MAP Approach for Joint Motion Estimation, Segmentation, and Super Resolution

by Huanfeng Shen, Liangpei Zhang, Bo Huang, Pingxiang Li - In IEEE Transactions on Image Processing , 2007
"... Abstract—Super resolution image reconstruction allows the re-covery of a high-resolution (HR) image from several low-resolu-tion images that are noisy, blurred, and down sampled. In this paper, we present a joint formulation for a complex super-reso-lution problem in which the scenes contain multipl ..."
Abstract - Cited by 21 (1 self) - Add to MetaCart
Abstract—Super resolution image reconstruction allows the re-covery of a high-resolution (HR) image from several low-resolu-tion images that are noisy, blurred, and down sampled. In this paper, we present a joint formulation for a complex super-reso-lution problem in which the scenes contain multiple independently moving objects. This formulation is built upon the maximum a pos-teriori (MAP) framework, which judiciously combines motion esti-mation, segmentation, and super resolution together. A cyclic coor-dinate descent optimization procedure is used to solve the MAP for-mulation, in which the motion fields, segmentation fields, and HR images are found in an alternate manner given the two others, re-spectively. Specifically, the gradient-based methods are employed to solve the HR image and motion fields, and an iterated condi-tional mode optimization method to obtain the segmentation fields. The proposed algorithm has been tested using a synthetic image sequence, the “Mobile and Calendar ” sequence, and the original “Motorcycle and Car ” sequence. The experiment results and error analyses verify the efficacy of this algorithm. Index Terms—Joint estimation, maximum a posteriori (MAP), motion estimation, segmentation, super resolution. I.
(Show Context)

Superresolution Images Reconstructed from Aliased Images

by Patrick Vandewalle, Sabine Süsstrunk, Martin Vetterli - U.S. DEPARTMENT OF AGRICULTURE, SCIENCE, AND EDUCATION ADMINISTRATION, CONSERVATION REPORT NO. 26 , 2003
"... In this paper, we present a simple method to almost quadruple the spatial resolution of aliased images. From a set of four low resolution, undersampled and shifted images, a new image is constructed with almost twice the resolution in each dimension. The resulting image is aliasing-free. A small ali ..."
Abstract - Cited by 18 (5 self) - Add to MetaCart
In this paper, we present a simple method to almost quadruple the spatial resolution of aliased images. From a set of four low resolution, undersampled and shifted images, a new image is constructed with almost twice the resolution in each dimension. The resulting image is aliasing-free. A small aliasing-free part of the frequency domain of the images is used to compute the exact subpixel shifts. When the relative image positions are known, a higher resolution image can be constructed using the Papoulis-Gerchberg algorithm. The proposed method is tested in a simulation where all simulation parameters are well controlled, and where the resulting image can be compared with its original. The algorithm is also applied to real, noisy images from a digital camera. Both experiments show very good results.