Linear filter banks and wavelet transforms have been widely researched and have many applications including sub-band image coding. For good performance the filter banks should posses the properties of both critical de...
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ISBN:
(纸本)085296692X
Linear filter banks and wavelet transforms have been widely researched and have many applications including sub-band image coding. For good performance the filter banks should posses the properties of both critical decimation and perfect reconstruction, which together imply that the sub-band representation is both complete and non-redundant. More recently non-linear filter banks satisfying the constraints of both critical decimation and perfect reconstruction have been proposed. Such filter banks allow the use of median and other non-linear operators, and have been shown to give improved subjective quality for image compression. The use of median operations gives the filters important out-lier rejection properties. This paper examines the use of non-linear filter banks for image compression and transmission over noisy channels. Example filters are designed using median operations and are shown to have an improved resilience to channel errors.
Binary Tree Predictive Coding (BTPC) is an efficient general-purpose still-image compression scheme, competitive with JPEG for natural image coding and with GIF for graphics. We report in this paper the extension of B...
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ISBN:
(纸本)085296692X
Binary Tree Predictive Coding (BTPC) is an efficient general-purpose still-image compression scheme, competitive with JPEG for natural image coding and with GIF for graphics. We report in this paper the extension of BTPC to video compression using motion estimation and compensation techniques which are simple, efficient, non-linear and predictive. The new method, Binary Tree Recursive Motion Estimation and Coding (BTRMEC), exploits the hierarchical structure of BTPC to give progressively refined motion estimates for increasing numbers of pels. Compression results for BTRMEC are compared against conventional block-based motion compensated coding as used in MPEG (i.e. with variable-length coding of motion vectors, and DCT/runlength coding of residues). They show that both BTRMEC and BTPC adapted to video coding are efficient methods to code video sequences.
Integer based-matrix algorithms for discrete Haar transform (DHT) and discrete wavelet transform (DWT) are proposed with relation to the multiresolution representation (MRR). A recursive wavelet transform technique is...
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ISBN:
(纸本)0819425915
Integer based-matrix algorithms for discrete Haar transform (DHT) and discrete wavelet transform (DWT) are proposed with relation to the multiresolution representation (MRR). A recursive wavelet transform technique is used with a view to demonstrating simply lossy reconstructed images in contrast to an original image under the specified resolution size. A visual effect of reconstructed images with differnt appearance and image quality, caused by modifying or throwing away a part of the 2-D HT or WT coefficients, is discussed with a measure of quantitative evaluation such as similarity and/or modified similarity, and fidelity RMSE and/or PSNR.
The variable length code design of a complete quadtree-based video codec is addressed, in which we jointly optimize the entropy-coding for the parameters of motion-compensated prediction together with the residual cod...
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ISBN:
(纸本)085296692X
The variable length code design of a complete quadtree-based video codec is addressed, in which we jointly optimize the entropy-coding for the parameters of motion-compensated prediction together with the residual coding. The quadtree coding scheme selected for this optimization allows easy access to the rate-distortion costs, thus making it possible to perform rate-distortion optimized bit allocation without exhaustive computation. Throughout the paper, we view the quadtree coder as a special case of tree-structured entropy-constrained vector quantization and derive a design algorithm which iteratively descents to a (locally) optimal quadtree video codec. Experimental results evaluate the performance of the proposed design algorithm.
Reliable and fast tracking of facial features in 'head and shoulders' scenes is of paramount importance for analysis of motion in model-based coding techniques. A new method of tracking the position of importa...
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ISBN:
(纸本)085296692X
Reliable and fast tracking of facial features in 'head and shoulders' scenes is of paramount importance for analysis of motion in model-based coding techniques. A new method of tracking the position of important facial features is presented here. The algorithm enables tracking of local motion of important facial features (eyes open-close, mouth open-close). It is therefore possible to determine not only the spatial location of the investigated facial feature, but also its shape. The method is based on eigenvalue decomposition of the sub-images extracted from the video sequence. The motion and shape of each facial feature is tracked separately. The algorithm can be used for tracking objects in scenes other than 'head-and-shoulders'.
A family of 2 dimensional detection modules based on 256x256 and 486x640 platinum silicide (PtSi) focal planes, or 128x128 and 256x256 mercury cadmium tellrrride (MCT) focal planes for applications in either the 3.5 m...
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ISBN:
(纸本)0819424765
A family of 2 dimensional detection modules based on 256x256 and 486x640 platinum silicide (PtSi) focal planes, or 128x128 and 256x256 mercury cadmium tellrrride (MCT) focal planes for applications in either the 3.5 mu m (MWIR) or 8.10 mu m (LWIR) range was recently developed by AIM. A wide variety of applications is covered by the specific features unique for these two material systems(1), The PtSi units provide state of the art correctability with long term stable gain and offset coefficients. The MCT units provide extremely fast frame rates like 400Hz with snapshot integration times as short as 250 mu s and with a thermal resolution NETD < 20mK for e.g. the 128x128 LWIR module. The unique design, idea general. for all of these modules is the exclusively digital interface, using 14 Bit analog to digital conversion to-provide state of the art correctability, access to highly dynamic scenes without any loss of information and simplified exchangeability of the units. Device specific features like bias voltages etc, are identified during the final test and stored in a memory on the driving electronics, This concept allows an easy exchange of IDCA's of the same type without any need for tuning or e.g, the possibility to upgrade a PtSi based unit to an MCT module by just loading the suitable software. Miniaturized digital signal processor (DSP) based image correction units were developed for testing and operating the units with output data rates of up to 16Mpixels/s. These boards provide the ability for freely programmable realtime functions like two point correction and various data manipulations in thermography applications. The main features of these modules are summarized together with measured performance data.
The most common approach to generating dense optical flow fields embeds the intensity constancy constraint within a multi-resolution framework using a Laplacian pyramid. Such a framework, in which motion estimates at ...
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ISBN:
(纸本)085296692X
The most common approach to generating dense optical flow fields embeds the intensity constancy constraint within a multi-resolution framework using a Laplacian pyramid. Such a framework, in which motion estimates at one scale are used to seed more accurate estimation at finer resolutions, has the potential ability to capture large motions, reducing the likelihood of aliasing. This approach, however, treats the image sequence as a series of independent processing problems where motion results from one frame do not inform the analysis of subsequent frames. In this work, this hierarchical framework is abandoned in favour of a feed-forward approach in which previous optical flow fields are fed forward (actually warped forward) to act as initial estimates in an affine fitting process in the next frame. The resulting simplified process architecture is not only fast but remarkably tolerant to very large pixel motions.
image intensifiers on board UVSTAR, the Ultraviolet Spectrograph Telescope for Astronomical Research, did not seem to be functioning as expected. Therefore, a simplified version of the UVSTAR electronics was used to t...
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ISBN:
(纸本)0819425869
image intensifiers on board UVSTAR, the Ultraviolet Spectrograph Telescope for Astronomical Research, did not seem to be functioning as expected. Therefore, a simplified version of the UVSTAR electronics was used to test the image intensifiers in the laboratory. All photosensitive locations of the intensifier army were exposed at once, and then each line read each sequentially. The images which were produced had an annoying intensity gradient superimposed on them. This gradient is due to the fact that line n of the intensifier array was corrupted by thermal signal n times longer than line 1. The imagery was further degraded by the presence of so-called ''hot pixels''. These pixels correspond to locations on the intensifier's charge coupled device (CCD) array which over react to the photon flux and produce abnormally high intensity readings. This paper describes imageprocessing techniques which removed the gradient as well as hot pixels from the intensifier imagery so that an accurate performance assessment could be made. The methods described can also be used to diagnose flaws in medical and industrial image intensifiers in general.
We propose a new optimizer for multiresolution image registration. It is adapted to a criterion known as mutual information and is well suited to inter-modality. Our iteration strategy is inspired by the Marquardt-Lev...
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ISBN:
(纸本)0819425915
We propose a new optimizer for multiresolution image registration. It is adapted to a criterion known as mutual information and is well suited to inter-modality. Our iteration strategy is inspired by the Marquardt-Levenberg algorithm, even though the underlying problem is not least-squares. We develop a framework based on a continuous polynomial spline representation of images. Together with the use of Parzen histogram estimates, it allows for closed-form expressions of the gradient and Hessian of the criterion. Tremendous simplifications result from the choice of Parzen windows satisfying the partition of unity, also based on B-splines. We use this framework to compute an image pyramid and to set our optimizer in a multiresolution context. We perform several experiments and show that it is particularly well adapted to a coarse-to-fine optimization strategy. We compare our approach to the popular Powell algorithm and conclude that our proposed optimizer is faster, at no cost in robustness or precision.
Developments in Markov Chain Monte Carlo procedures have made it possible to perform fully Bayesian image seg mentation. By this we mean that all the parameters are treated identically, be they the segmentation labels...
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ISBN:
(纸本)0818681837
Developments in Markov Chain Monte Carlo procedures have made it possible to perform fully Bayesian image seg mentation. By this we mean that all the parameters are treated identically, be they the segmentation labels, the class parameters or the Markov Random Field prior parameters. We perform the analysis by sampling from the posterior distribution of all the parameters. Sampling from the MRF parameters has traditionally been considered if not intractable then at least computationally prohibitive. In the statistics literature there are descriptions of experiments showing that the MRF parameters may be sampled by approximating the partition function. These experiments are all, however, on 'toy' problems - for the typical size of image encountered in engineering applications phase transition behaviour of the models becomes a major limiting factor in the estimation of the partition function. Nevertheless, we show that, with some care, fully Bayesian segmentation can be performed on realistic sized images. We also compare the fully Bayesian approach with the approximate pseudolikelihood method.
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