850 research outputs found
Clío. Musa I (con un'appendice tratta dalla Musa Melpómene) a cura di A. Martinengo, F. Cappelli e B. Garzelli
No full textEfficient MMSE pansharpening based on non-local optimization
No full textThe paper presents a pansharpening algorithm that finds an optimal linear solution, in the MMSE sense, following a generalized component-substitution approach. It is characterized by nonlocal parameter optimization obtained through K-means clustering. The proposed method, namely C-BDSD, solves the problem of context-adaptive schemes that tune the spatial injection parameters on local statistics: instabilities and blockiness artifacts are avoided and the estimation phase is improved. The C-BDSD algorithm is accurate and fast, and can be also applied to spatially enhance large-size multi-spectral images. Very high quality scores and excellent visual quality of the fused images demonstrate the validity of the method
SAR image analysis of the sea surface by local fractal dimension estimation
No full textA wavelet-based approach to local fractal dimension estimation of SAR images of the sea surface is presented. Fractal analysis is considered as a tool for image texture characterization which can play a fundamental role to automatically detect oil slicks, and possibly distinguish them from natural surface films. A fractional Brownian motion (fBm) model is assumed for the clean sea surface. FBm processes have been proved to be suitable to describe signals backscattered by many natural surfaces, particularly by the sea surface within a certain range of scales. By using the properties of the average power spectra of fBm's, it is possible to estimated the fractal dimension, as demonstrated on synthetic fBm realizations. In this paper, a redundant wavelet representation is applied for estimating the local fractal dimension of the sea surface. By using this technique, which allows to operate at the original image resolution, all discontinuities of the fractal sea surface can be detected and accurately localized. Experimental results on true SAR images show that without considering the backscatter coefficient for calculating the fractal dimension, but only textural features, it is possible to detect oil slicks and man-made objects on the sea surface
Oil-spills detection in SAR images by fractal dimension estimation
No full textThe paper describes a multi-resolution algorithm based on fractal geometry for texture analysis and detection of oil spills in SAR images. The multi-resolution approach reduces the problems of speckle and sea clutter and preserves subtle variations of oil slicks. The use of fractal dimension as a feature for classification improves the oil spill detection, since enhances texture discrimination. The proposed approach computes the fractal dimension from power spectra: the ratio between powers at different scales is straightforwardly related to fractal dimension. The proposed method to compute a fractal signature is based on the multi-scale image decomposition obtained by the Normalized Laplacian Pyramid which provides a reliable estimation of the fractal dimension even in the presence of speckle
Possibilities and limitations of the use of wavelets in image fusion
No full textThe paper reviews some of the most efficient wavelet approaches to image fusion for remote sensing applications and indicates open issues and future trends of this remarkable research. For the particular topic of spatial enhancement in multi-resolution image fusion, quality assessment of the fused image is considered. An objective analysis is described, based on both global and local score indexes. The problem of reducing possible visual artifacts is also discussed
Annarosa Garzelli. Miniatura fiorentina del Rinascimento. 1440-1525. Un primo censimento, a cura di Annarosa Garzelli. I. Le immagini, gli autori, i destinatari di Annarosa Garzelli ; New research on humanistic scribes in Florence di Albinia de la Mare. II. Illustrazioni. 1985
No full textBauer-Eberhardt Ulrike. Annarosa Garzelli. Miniatura fiorentina del Rinascimento. 1440-1525. Un primo censimento, a cura di Annarosa Garzelli. I. Le immagini, gli autori, i destinatari di Annarosa Garzelli ; New research on humanistic scribes in Florence di Albinia de la Mare. II. Illustrazioni. 1985. In: Scriptorium, Tome 41 n°1, 1987. pp. 173-175
Type-II hybrid ARQ protocol using concatenated codes
No full textThe high throughput achieved by type-II hybrid automatic repeat request (ARQ) protocols can be enhanced by using the inner structure of a codeword in a concatenated coding scheme. The paper presents a new type-II hybrid scheme based on concatenated codes to which two retransmission strategies have been applied. The results on throughput bounds show that the proposed protocols are effective even in the case of communication channels with high error rates
Context-driven image fusion of multispectral and panchromatic data based on a redundant wavelet representation
No full textA method of image data fusion is proposed, which applies a stationary or redundant wavelet decomposition to merge multispectral and panchromatic images. Couples of subbands of corresponding frequency content are locally merged if a correlation condition is satisfied, and the fused image is produced by taking the inverse transform. A local correlation coefficient between the low-frequency subband of the high-resolution image and the corresponding subband of the up-sampled multispectral image is used in order to pilot the fusion process. The experimental results prove that the method incorporates contextual spatial information and reduces possible over-enhancement of the multispectral data on the image regions having higher spectral content, as in the case of urban areas or other highly textured regions
Fusion of Panchromatic and Multispectral Images by Genetic Algorithms
No full textPan-sharpened MS is a fusion product in which the multispectral (MS) bands are spatially enhanced by the higher-resolution panchromatic (Pan) image. Most effective algorithms for pan-sharpening are based on multiresolution analysis (MRA), e.g., wavelets, Laplacian pyramids, wavelet frames, or curvelets. MRA approaches present one main critical point: filtering operations may produce ringing artifacts when high frequency details are extracted from the panchromatic image. In this paper, a pan-sharpening algorithm for 4-band MS data is proposed, which is not based on MRA, but it applies a Generalized Intensity-Hue-Saturation (GIHS) transformation to the MS bands. A genetic algorithm is adopted to define the injection model which establishes how the missing highpass information is extracted from the Pan image. The fitness function of the genetic algorithm which provides the algorithm parameters driving the fusion process is based on a quality index specifically designed for quality assessment of,4-band MS images. Both visual and objective comparisons with advanced fusion methods are presented on QuickBird image data
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