Processing of Façade Imagery

Modeling and reconstruction of urban environments is currently the subject of intensive research. There is a wide range of possible applications, including virtual environments like cyber-tourism, computer games, and the entertainment industries in general, as well as urban planning and architecture, security planning and training, traffic simulation, driving guidance and telecommunications, to name but a few. The research directions are spread across the disciplines of computer vision, computer graphics, image processing, photogrammetry and remote sensing, as well as architecture and the geosciences. Reconstruction is a complex problem and requires an entire pipeline of different tasks. In this thesis we focus on processing of images of façades which is one specific subarea of urban reconstruction. The goal of our research is to provide novel algorithmic solutions for problems in façade imagery processing. In particular, the contribution of this thesis is the following: First, we introduce a system for generation of approximate orthogonal façade images. The method is a combination of automatic and interactive tools in order to provide a convenient way to generate high-quality results. The second problem addressed in this thesis is façade image segmentation. In particular, usually by segmentation we mean the subdivision of the façade into windows and other architectural elements. We address this topic with two different algorithms for detection of grids over the façade image. Finally, we introduce one more façade processing algorithm, this time with the goal to improve the quality of the façade appearance. The algorithm propagates visual information across the image in order to remove potential obstacles and occluding objects. The output is intended as source for textures in urban reconstruction projects. The construction of large three-dimensional urban environments itself is beyond the scope of this thesis. However, we propose a suite of tools together with mathematical foundations that contribute to the state-of-the-art and provide helpful building blocks important for large scale urban reconstruction projects.