2,182 research outputs found
Image Super-Resolution Using Adaptive 2-D Gaussian Basis Function Interpolation
Digital image interpolation using Gaussian radial basis functions has been implemented by several investigators, and promising results have been obtained; however, determining the basis function variance has been problematic. Here, adaptive Gaussian basis functions fit the mean vector and covariance matrix of a non-radial Gaussian function to each pixel and its neighbors, which enables edges and other image characteristics to be more effectively represented. The interpolation is constrained to reproduce the original image mean gray level, and the mean basis function variance is determined using the expected image smoothness for the increased resolution. Test outputs from the resulting Adaptive Gaussian Interpolation algorithm are presented and compared with classical interpolation techniques
Scanamorphos: a map-making software for Herschel and similar scanning bolometer arrays
Scanamorphos is one of the public softwares available to post-process scan
observations performed with the Herschel photometer arrays. This
post-processing mainly consists in subtracting the total low-frequency noise
(both its thermal and non-thermal components), masking high-frequency artefacts
such as cosmic ray hits, and projecting the data onto a map. Although it was
developed for Herschel, it is also applicable with minimal adjustment to scan
observations made with some other imaging arrays subjected to low-frequency
noise, provided they entail sufficient redundancy; it was successfully applied
to P-Artemis, an instrument operating on the APEX telescope. Contrary to
matrix-inversion softwares and high-pass filters, Scanamorphos does not assume
any particular noise model, and does not apply any Fourier-space filtering to
the data, but is an empirical tool using purely the redundancy built in the
observations -- taking advantage of the fact that each portion of the sky is
sampled at multiple times by multiple bolometers. It is an interactive software
in the sense that the user is allowed to optionally visualize and control
results at each intermediate step, but the processing is fully automated. This
paper describes the principles and algorithm of Scanamorphos and presents
several examples of application.Comment: This is the final version as accepted by PASP (on July 27, 2013). A
copy with much better-quality figures is available on
http://www2.iap.fr/users/roussel/herschel
Single frame super-resolution image system
The estimation of some unknown quantity information from known observable information can be viewed as a specific statistical process which needs an extra source of information prediction strategy. In this regard, image super-resolution is an important application In this thesis, we proposed a new image interpolation method based on Redundant Discrete Wavelet Transform (RDWT) and self-adaptive processes in which edge direction details are considered to solve single-frame image super-resolution task. Information about sharp variations, both in horizontal and vertical directions derived from wavelet transform sub-bands are considered, followed by detection and modification of the aliasing part in the preliminary output in order to increase the visual effect. By exploiting fundamental properties of images such as property of edge direction, different parts of the source image are considered separately in order to predict the vertical and horizontal details accurately, helping to consummate the whole framework in reconstructing the high-resolution image. Extensive tests of the proposed method show that both objective quality (PSNR) and subjective quality are obviously improved compared to several other state-of-the-art methods. And this work also leaved capacious space for further research, not only theoretical but also practical. Some of the related research applications based on this algorithm strategy are also briefly introduced
Near-UV OH Prompt Emission in the Innermost Coma of 103P/Hartley 2
The Deep Impact spacecraft fly-by of comet 103P/Hartley 2 occurred on 2010
November 4, one week after perihelion with a closest approach (CA) distance of
about 700 km. We used narrowband images obtained by the Medium Resolution
Imager (MRI) onboard the spacecraft to study the gas and dust in the innermost
coma. We derived an overall dust reddening of 15\%/100 nm between 345 and 749
nm and identified a blue enhancement in the dust coma in the sunward direction
within 5 km from the nucleus, which we interpret as a localized enrichment in
water ice. OH column density maps show an anti-sunward enhancement throughout
the encounter except for the highest resolution images, acquired at CA, where a
radial jet becomes visible in the innermost coma, extending up to 12 km from
the nucleus. The OH distribution in the inner coma is very different from that
expected for a fragment species. Instead, it correlates well with the water
vapor map derived by the HRI-IR instrument onboard Deep Impact
\citep{AHearn2011}. Radial profiles of the OH column density and derived water
production rates show an excess of OH emission during CA that cannot be
explained with pure fluorescence. We attribute this excess to a prompt emission
process where photodissociation of HO directly produces excited
OH*() radicals. Our observations provide the first direct
imaging of Near-UV prompt emission of OH. We therefore suggest the use of a
dedicated filter centered at 318.8 nm to directly trace the water in the coma
of comets.Comment: 21 page
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Intelligent Side Information Generation in Distributed Video Coding
Distributed video coding (DVC) reverses the traditional coding paradigm of complex encoders allied with basic decoding to one where the computational cost is largely incurred by the decoder. This is attractive as the proven theoretical work of Wyner-Ziv (WZ) and Slepian-Wolf (SW) shows that the performance by such a system should be exactly the same as a conventional coder. Despite the solid theoretical foundations, current DVC qualitative and quantitative performance falls short of existing conventional coders and there remain crucial limitations. A key constraint governing DVC performance is the quality of side information (SI), a coarse representation of original video frames which are not available at the decoder. Techniques to generate SI have usually been based on linear motion compensated temporal interpolation (LMCTI), though these do not always produce satisfactory SI quality, especially in sequences exhibiting non-linear motion.
This thesis presents an intelligent higher order piecewise trajectory temporal interpolation (HOPTTI) framework for SI generation with original contributions that afford better SI quality in comparison to existing LMCTI-based approaches. The major elements in this framework are: (i) a cubic trajectory interpolation algorithm model that significantly improves the accuracy of motion vector estimations; (ii) an adaptive overlapped block motion compensation (AOBMC) model which reduces both blocking and overlapping artefacts in the SI emanating from the block matching algorithm; (iii) the development of an empirical mode switching algorithm; and (iv) an intelligent switching mechanism to construct SI by automatically selecting the best macroblock from the intermediate SI generated by HOPTTI and AOBMC algorithms. Rigorous analysis and evaluation confirms that significant quantitative and perceptual improvements in SI quality are achieved with the new framework
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