Browsing by Author "Almeida, D."
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- An integrated framework for combining gist vision with object segregation categorisation and recognitionPublication . Rodrigues, J. M. F.; Almeida, D.; Martins, Jaime; Lam, RobertoThere are roughly two processing systems: (1) very fast gist vision of entire scenes, completely bottom-up and data driven, and (2) Focus-of-Attention (FoA) with sequential screening of specific image regions and objects. The latter system has to be sequential because unnormalised input objects must be matched against normalised templates of canonical object views stored in memory, which involves dynamic routing of features in the visual pathways.
- Building the what and where systems: multi-scale lines, edges and keypointsPublication . Rodrigues, J. M. F.; Almeida, D.; Nunes, S.; Lam, Roberto; du Buf, J. M. H.Computer vision for realtime applications requires tremendous computational power because all images must be processed from the first to the last pixel. Ac tive vision by probing specific objects on the basis of already acquired context may lead to a significant reduction of processing. This idea is based on a few concepts from our visual cortex (Rensink, Visual Cogn. 7, 17-42, 2000): (1) our physical surround can be seen as memory, i.e. there is no need to construct detailed and complete maps, (2) the bandwidth of the what and where systems is limited, i.e. only one object can be probed at any time, and (3) bottom-up, low-level feature extraction is complemented by top-down hypothesis testing, i.e. there is a rapid convergence of activities in dendritic/axonal connections.
- Fine arts edutainment: the amateur painterPublication . Almeida, D.; Carvalho, Brito; Rodrigues, J. M. F.; du Buf, J. M. H.; Nunes, S.A new scheme for painterly rendering (NPR) has been developed. This scheme is based on visual perception, in particular themulti-scale line/edge representation in the visual cortex. The Amateur Painter (TAP) is the user interface on top of the rendering scheme. It allows to (semi)automatically create paintings from photographs, with different types of brush strokes and colour manipulations. In contrast to similar painting tools, TAP has a set of menus that reflects the procedure followed by a normal painter. In addition, menus and options have been designed such that they are very intuitive, avoiding a jungle of sub-menus with options from image processing that children and laymen do not understand. Our goal is to create a tool that is extremely easy to use, with the possibility that the user becomes interested in painting techniques, styles, and fine arts in general.
- Object categorisations using templates constructed from multi-scale line and edge representationsPublication . Nunes, S.; Almeida, D.; Rodrigues, J. M. F.; du Buf, J. M. H.Object categorisation is linked to detection, segregation and recognition. In the visual system, these processes are achieved in the ventral \what"and dorsal \where"pathways [3], with bottom-up feature extractions in areas V1, V2, V4 and IT (what) in parallel with top-down attention from PP via MT to V2 and V1 (where). The latter is steered by object templates in memory, i.e. in prefrontal cortex with a what component in PF46v and a where component in PF46d.
- Overview of greenhouse horticulture in Portugal: technology and environmentPublication . Costa, J. M.; Reis, Mário; Palha, M. G.; Passarinho, J. A.; Carvalho, S. M. P.; Almeida, D.; Nunes, L.; Ferreira, M. E.Total greenhouse production area in Portugal is about 3,000 ha with a tendency for expansion, and tomato is the most important greenhouse crop. Protected cultivation in Portugal modernized in recent decades but remains heterogeneous in terms of technology, yields and management. The sector organizational structure and technological trajectory is characterized by increased greenhouse area per grower and higher volume/covered area ratio, and soilless cultivation has expanded. Therefore, less expensive alternatives may arise as the common solution for the sector. Most of the greenhouse area (about 75%) corresponds to single and multiple plastic tunnels with semi automatic or automatic climate control. The use of glasshouses with fully controlled environment remains minor, due to the high costs of equipment, energy consumption, and limited expertise and technical support for local conditions. Greenhouse horticulture has an undesirable environmental impact which must be properly monitored and minimized, while guaranteeing its socio-economic benefits. In addition, there is more strict environmental EU legislation and stakeholders are more informed which puts pressure on the greenhouse industry in order to use more efficiently resources and minimize its environmental impact. However, the Portuguese sector still lacks relevant quantitative information and standards on performance indicators, e.g. resource use efficiency (e.g. water, energy) and related economic/environmental performance. A SWOT analysis is presented for the most important greenhouse production areas in Portugal and guidelines are suggested for more competitive and environmental sustainable greenhouse production.
- Painterly rendering using human visionPublication . du Buf, J. M. H.; Rodrigues, J. M. F.; Nunes, S.; Almeida, D.; Brito, Vera; Carvalho, J.Painterly rendering has been linked to computer vision, but we propose to link it to human vision because perception and painting are two processes that are interwoven. Recent progress in developing computational models allows to establish this link. We show that completely automatic rendering can be obtained by applying four image representations in the visual system: (1) colour constancy can be used to correct colours, (2) coarse background brightness in combination with colour coding in cytochrome-oxidase blobs can be used to create a background with a big brush, (3) the multi-scale line and edge representation provides a very natural way to render fi ner brush strokes, and (4) the multi-scale keypoint representation serves to create saliency maps for Focus-of-Attention, and FoA can be used to render important structures. Basic processes are described, renderings are shown, and important ideas for future research are discussed.
- Perception-based painterly rendering: funcionality and interface designPublication . Nunes, S.; Almeida, D.; Brito, Vera; Carvalho, J.; Rodrigues, J. M. F.; du Buf, J. M. H.Painterly rendering (non-photorealistic rendering or NPR) aims at translating photographs into paintings with discrete brush strokes, simulating certain techniques (im- or expressionism) and media (oil or watercolour). Recently, our research into visual perception and models of processes in the visual cortex resulted in a new rendering scheme, in which detected lines and edges at different scales are translated into brush strokes of different sizes. In order to prepare a version which is suitable for many users, including children, the design of the interface in terms of window and menu system is very important. Discussions with artists and non-artists led to three design criteria: (1) the interface must reflect the procedures and possibilities that real painters follow and use, (2) it must be based on only one window, and (3) the menu system must be very simple, avoiding a jungle of menus and sub-menus. This paper explains the interface that has been developed.
- Polygon optimisation for the modelling of planar range dataPublication . Nunes, S.; Almeida, D.; Loke, R. E.; du Buf, J. M. H.In this paper we present efficient and fast algorithms for the reconstruction of scenes or objects using range image data. Assuming that a good segmentation is available, we concentrate on the polygonisation, triangulation and optimisation, i.e. both triangle reduction and adaptive edge filtering to improve edge linearity. In the processing, special attention is given to complex edge junctions. In a last step, vertex neighbourhoods are analysed in order to robustly attribute depth to the triangle list from the noisy range data.