Uso da constância de cor na robótica móvel

• Autor(a) principal: Almonfrey, Douglas
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/9615
• topic: Constância de cor; Circuitos Elétricos, Magnéticos e Eletrônicos; Processamento de imagens; Navegação de robôs móveis; Robótica; 621.3

The color captured by a camera is function of the scene illumination, the reflective characteristics of the surfaces in the scene, the photosensors in the vision systems and mainly the processing made by the brain. Due to this processing performed by the brain, humans show the color constancy phenomenon: the color of a surface is perceived as the same regardless of the environment illumination conditions. However, the variation in the scene illumination implies a change in the color value of a surface registered by an artificial vision system. In the literature, defining surface descriptors that are independent of the illumination is known as color constancy problem. One solution to this problem is to obtain the reflective characteristics of the surfaces apart from the information of the scene illumination. Another approach to solve the color constancy problem is to convert the colors of the surfaces in the image so that the surfaces appear to be always under influence of the same standard illumination. Independently of the chosen approach, this is a hard problem to solve and most existing theories are applied only to synthesized images while others present a limited performance when applied to real images of environments under uncontrolled illumination. Due to the absence of the color constancy phenomenon in artificial vision systems, many automatic systems avoid the use of color information obtained from images captured by these systems. Besides that, the solution of the color constancy problem is also desired by the consumer photography industry. In this context, this work addresses the solution of the color constancy problem using an algorithm based on the color correction method presented in (KONZEN; SCHNEEBELI, 2007a). This algorithm corrects colors of a scene captured under unknown illumination so that the scene appears to have been captured under the influence of a standard illumination. If the scene illumination is always the same, the colors of the images show color constancy. This conversion between illuminations is performed by knowing the colors of some points in the scene under the influence of the standard illumination. Finally, we analyze the color constancy algorithm performance by applying it to a sequence of images of scenes subjected to abrupt illumination changes. Also a color based tracking is employed to show the importance of the color constancy algorithm in these scenes. Besides that, a color based visual-servo control working together with the color constancy algorithm is employed to guide a robot in an outdoor navigation task through an environment subjected to the variable illumination of the sun. The color constancy algorithm is also applied on images of an external environment that present illumination changes and the discussion of its utilization in place recognition, a fundamental task in robot localization, is made.