Sparsity and `Something Else': An Approach to Encrypted Image Folding

A property of sparse representations in relation to their capacity for information storage is discussed. It is shown that this feature can be used for an application that we term Encrypted Image Folding. The proposed procedure is realizable through any suitable transformation. In particular, in this paper we illustrate the approach by recourse to the Discrete Cosine Transform and a combination of redundant Cosine and Dirac dictionaries. The main advantage of the proposed technique is that both storage and encryption can be achieved simultaneously using simple processing steps.Comment: Revised manuscript- Software for implementing the Encrypted Image Folding proposed in this paper is available on http://www.nonlinear-approx.info

Sparse image representation with encryption

In this thesis we present an overview of sparse approximations of grey level images. The sparse representations are realized by classic, Matching Pursuit (MP) based, greedy selection strategies. One such technique, termed Orthogonal Matching Pursuit (OMP), is shown to be suitable for producing sparse approximations of images, if they are processed in small blocks. When the blocks are enlarged, the proposed Self Projected Matching Pursuit (SPMP) algorithm, successfully renders equivalent results to OMP. A simple coding algorithm is then proposed to store these sparse approximations. This is shown, under certain conditions, to be competitive with JPEG2000 image compression standard. An application termed image folding, which partially secures the approximated images is then proposed. This is extended to produce a self contained folded image, containing all the information required to perform image recovery. Finally a modified OMP selection technique is applied to produce sparse approximations of Red Green Blue (RGB) images. These RGB approximations are then folded with the self contained approach

Satellite Snow Surveillance -A Down to Earth Use of Space Technology

In the not-too-distant future, an increasing use will be made of earth-orbiting satellites to survey our natural resources. One resource that has been observed from space since the first meteorological satellite nearly a decade ago, is the earth\u27s snow cover. Continued observation of this resource will be a prime use of satellite systems designed specifically to view the earth1 s surface; in fact, a survey of snow and ice on a world-wide scale, as planned in the International Hydrological Decade, appears economically feasible only through the use of satellite observations. Thus, snow surveillance is a really down-to-earth use of space technology. Recent studies of the use of satellite photography to map snow cover distributions in the Upper Mississippi-Missouri River Basins Region are described in this paper. The techniques presented for identifying and mapping snow distributions, and for estimating snow depths, were developed originally from TIROS photography, * and were tested on a data sample obtained from the ESSA satellites. 2 Additional research is currently in progress to determine whether these techniques developed for the relatively flat terrain of the north-central United States are also applicable to mountainous areas. This research is briefly reviewed, and the outlook for operational snow surveillance from space is discussed

The Use of Satellite Cloud Photography to Infer Oceanographic Phenomena

Several years of satellite cloud photography were examined to determine to what extent oceanographic phenomena might be revealed through their influence on the local cloud structure. The region of the Peru Current was selected for the study. As anticipated, indications of known oceanographic features including the Peru Current itself and local upwelling centers were noted. Previously unknown features such as an apparent band of warmer water off the Peruvian coast and anomalous patches of calm water in mid-ocean were also found. A seasonal cloud climatology for the Peru Current area was developed. The importance of coordinated studies using satellites, ships and aircraft is emphasized

Sparse Representation of Astronomical Images

Sparse representation of astronomical images is discussed. It is shown that a significant gain in sparsity is achieved when particular mixed dictionaries are used for approximating these types of images with greedy selection strategies. Experiments are conducted to confirm: i)Effectiveness at producing sparse representations. ii)Competitiveness, with respect to the time required to process large images.The latter is a consequence of the suitability of the proposed dictionaries for approximating images in partitions of small blocks.This feature makes it possible to apply the effective greedy selection technique Orthogonal Matching Pursuit, up to some block size. For blocks exceeding that size a refinement of the original Matching Pursuit approach is considered. The resulting method is termed Self Projected Matching Pursuit, because is shown to be effective for implementing, via Matching Pursuit itself, the optional back-projection intermediate steps in that approach.Comment: Software to implement the approach is available on http://www.nonlinear-approx.info/examples/node1.htm

Reduced thermodynamic description of phase separation in a quasi-one-dimensional granular gas

We describe simulations of a quasi-one-dimensional, vibrated granular gas which exhibits an apparent phase separation into a liquidlike phase and a gaslike phase. In thermal equilibrium, such a phase separation in one dimension is prohibited by entropic considerations. We propose that the granular gas minimizes a function of the conserved mechanical variables alone: the particle number and volume. Simulations in small cells can be used to extract the equation of state and predict the coexisting pressure and densities, as confirmation of the minimization principle. Fluctuations in the system manifest themselves as persistent density waves but they do not destroy the phase-separated state

Local elites and social control: Building council houses in Stirling between the wars

This article examines the role played by local councillors in constructing new housing in Scotland during the inter-war period. Rather than view local authorities as simply the objective agency of central government's ambitions to construct council houses, we argue that the self-interest and motivations of councillors have to be recognized as significant factors in this process. It is argued also that the concerns of private landlords were neither ignored nor sacrificed in the rush to build new housing. Rather, given that councils remained dominated by local business men, many of whom were private landlords, councillors acted in ways to protect their own material and class interests. In so doing, they consciously, if implicitly, shaped the social geography of twentieth-century Scotland

Self-contained encrypted image folding

The recently introduced approach for Encrypted Image Folding is generalized to make it self-contained. The goal is achieved by enlarging the folded image so as to embed all the necessary information for the image recovery. The need for extra size is somewhat compensated by considering a transformation with higher folding capacity. Numerical examples show that the size of the resulting cipher image may be significantly smaller than the plain text one. The implementation of the approach is further extended to deal also with color images.Instituto de Física La Plat