Strong edge features for image coding

A two-component model is proposed for perceptual image coding. For the first component of the model, the watershed operator is used to detect strong edge features. Then, an efficient morphological interpolation algorithm reconstructs the smooth areas of the image from the extracted edge information, also known as sketch data. The residual component, containing fine textures, is separately coded by a subband coding scheme. The morphological operators involved in the coding of the primary component perform very efficiently compared to conventional techniques like the LGO operator, used for the edge extraction, or the diffusion filters, iteratively applied for the interpolation of smooth areas in previously reported sketch-based coding schemes.Peer ReviewedPostprint (published version

New approaches to texture coding in segmentation and feature-based image coding schemes

Peer ReviewedPostprint (published version

Coding of details in very low bit-rate video systems

In this paper, the importance of including small image features at the initial levels of a progressive second generation video coding scheme is presented. It is shown that a number of meaningful small features called details should be coded, even at very low data bit-rates, in order to match their perceptual significance to the human visual system. We propose a method for extracting, perceptually selecting and coding of visual details in a video sequence using morphological techniques. Its application in the framework of a multiresolution segmentation-based coding algorithm yields better results than pure segmentation techniques at higher compression ratios, if the selection step fits some main subjective requirements. Details are extracted and coded separately from the region structure and included in the reconstructed images in a later stage. The bet of considering the local background of a given detail for its perceptual selection breaks the concept ofPeer ReviewedPostprint (published version

Prediction error image coding using a modified stochastic vector quantization scheme

The objective of this paper is to provide an efficient and yet simple method to encode the prediction error image of video sequences, based on a stochastic vector quantization (SVQ) approach that has been modified to cope with the intrinsic decorrelated nature of the prediction error image of video signals. In the SVQ scheme, the codewords are generated by stochastic techniques instead of being generated by a training set representative of the expected input image as is normal use in VQ. The performance of the scheme is shown for the particular case of segmentation-based video coding although the technique can be also applied to motion-compensated hybrid coding schemes.Peer ReviewedPostprint (published version

Morphological filter for lossless image subsampling

We present a morphological filter for lossless image subsampling for a given downsampling-upsampling strategy. This filter is applied in a multiresolution decomposition and results in a more efficient scheme for image coding purposes than other lossy sampling schemes. Its main advantage is a greatly reduced computational load compared to multiresolution schemes performed with linear filters.Peer ReviewedPostprint (published version

Retrobant el sentit humà del paisatge natural

En el present article, m'agradaria proposar caminar per un recorregut imaginari de la nostra evolució individual i col·lectiva, per la nostra evolució paisatgística natural i humana. Com a éssers vius, hem observat el paisatge al llarg del temps i sembla que ens hem convençut plenament que hi és per observar-lo des de fora, com a accessori per admirar-lo o transformar-lo sense sentir-nos veritablement com a part integrant. Si no fos així, no s'explicaria la transformació que per l'acció humana s'ha produït i que, a hores d'ara, ens mostra el perill de viure en una espècie d'amnèsia de consciència i de sensibilitat. Sembla que la cosmovisió que altres cultures diferents a la nostra han pogut preservar hagi esdevingut en l'anomenat món desenvolupat una mena d'exotisme espiritual que produeix estranyesa, però al qual es recorre quan la resposta al desequilibri no es troba en la superficialitat i la pressa. Aquesta premissa ja fa molt de temps que, com a éssers humans, la coneixem i ha estat present durant l'evolució de la humanitat en una dimensió indestriable a la naturalesa. L'harmonia dels elements que composen la natura, i consegüentment l'home i la dona, confereix l'equilibri necessari per a la vida i la mort.In this article I would like to propose a trip along an imaginary route of our individual and collective evolution, through our natural landscape and human evolution. As living beings we have observed the landscape over time and we seem to be fully convinced that it is there to be observed from outside, as an accessory to admire or transform it without really feeling part of it. If this were not so it would not be possible to explain the transformation caused by the action of man and which now shows us how dangerous it is to live in a kind of amnesia of consciousness and sensitivity. It seems that the cosmo vision that cultures other than our own have managed to preserve has become, in the socalled developed world, a kind of spiritual exoticism that strikes us as strange but which we resort to when the answer to the disequilibrium cannot be found in hurried superficiality. This premise which we as humans have known for a long time and has been present throughout the evolution of mankind in a dimension that cannot be separated from nature. The harmony of the elements of nature, and consequently man and woman, afford the necessary equilibrium for life and death

A new approach to texture coding using stochastic vector quantization

A new method for texture coding which combines 2-D linear prediction and stochastic vector quantization is presented in this paper. To encode a texture, a linear predictor is computed first. Next, a codebook following the prediction error model is generated and the prediction error is encoded with VQ, using an algorithm which takes into account the pixels surrounding the block being encoded. In the decoder, the error image is decoded first and then filtered as a whole, using the prediction filter. Hence, correlation between pixels is not lost from one block to another and a good reproduction quality can be achieved.Peer ReviewedPostprint (published version

An efficient technique of texture representation in segmentation-based image coding schemes

In segmentation-based image coding techniques the image to be compressed is first segmented. Then, the information is coded describing the shape and the interior of the regions. A new method to encode the texture obtained in segmentation-based coding schemes is presented. The approach combines 2-D linear prediction and stochastic vector quantization. To encode a texture, a linear predictor is computed first. Next, a codebook following the prediction error model is generated and the prediction error is encoded with VQ. In the decoder, the error image is decoded first and then filtered as a whole, using the prediction filter. Hence, correlation between pixels is not lost from one block to another and a good reproduction quality can be achieved.Peer ReviewedPostprint (published version

Arqueomagnetisme, contribucions a l'estudi i valorització del patrimoni

La publicació de quatre articles al Journal of Archaeological Science sobre investigacions arqueomagnètiques a Catalunya i Tunísia consolida aquesta línia de recerca al departament de Geologia de la UAB. En aquest article s'explica què és l'arqueomagnetisme i es donen detalls sobre les investigacions dutes a terme en jaciments púnics i romans. Aquest tipus de recerca contribueix a millorar el coneixement històric i a datar jaciments arqueològics, una tasca important per a valoritzar el patrimoni arqueològic.La publicación de cuatro artículos en el Journal of Archaeological Science sobre investigaciones arqueomagnéticas en Cataluña y Túnez consolida esta línea de investigación en el Departamento de Geología de la UAB. En este artículo se explica qué es el arqueomagnetismo y se dan detalles sobre las investigaciones llevadas a cabo en yacimientos púnicos y romanos. Este tipo de investigación contribuye a mejorar el conocimiento histórico y a datar yacimientos arqueológicos, una tarea importante para valorizar el patrimonio arqueológico.The publication of four articles in the Journal of Archaeological Science dealing with archaeomagnetic studies in Catalonia and Tunisia consolidates this research line within the UAB Department of Geology. This popular science article describes what archaeomagnetism is and details are given on the research undertaken at Punic and Roman sites. These types of investigations contribute to improving historical knowledge and dating archaeological sites, an important task in the promotion of archaeological heritage

En arqueomagnetisme ho podem fer millor

El trasllat de dades geomagnètiques al llarg de distàncies de centenars de quilòmetres, suposant que el camp terrestre és dipolar, és una pràctica comuna en arqueomagnetisme. Els errors associats a procedir d'aquesta manera gairebé mai es tenen en compte. Aquest treball analitza la distribució d'aquests errors en l'espai i en el temps i n'extreu conclusions útils per als arqueomagnetistes.El traslado de datos geomagnéticos a lo largo de distancias de centenares de kilómetros suponiendo que el campo terrestre es dipolar es una práctica común en arqueomagnetismo. Los errores asociados a proceder de esta manera casi nunca se tienen en cuenta. Este trabajo analiza la distribución de estos errores en el espacio y el tiempo y extrae conclusiones útiles para los arqueomagnetistas.The relocation of geomagnetic data across distances of hundreds of kilometers and assuming a dipolar geomagnetic field is a common practice in archaeomagnetism. The errors due to this practice are rarely taken into account. This work analyses the time and space distribution of these errors and some useful conclusions for archaeomagnetists have been highlighted