Christopher Bulla

Learn More
The presence of aquatic macrophytes is a key factor in the selection of habitats by fish in floodplain lakes because these plants enhance the physical and biological complexities of aquatic habitats. The seasonal flood pulse may influence this interaction, but there is no information in the literature about the effects that flood events may have on(More)
In a modern video conferencing application, the people participating at each client can be detected, tracked and placed in a virtual scene where all persons are of equal size and occupy a predefined rectangular space. This virtual scene can then be rendered on screen instead of a whole room with several people. As a result, a more immerse video conferencing(More)
In this paper, we present an affine invariant feature descriptor, which is based on the well known Scale Invariant Feature Transform algorithm. The descriptor is a weighted histogram of gradient orientations and invariant against scale, in-plane rotation, stretch and skew. To cover the geometrical distortions introduced by an affine image transformation, we(More)
In this paper, we present a region of interest encoding system for video conference applications. We will utilize the fact that the main focus in a typical video conference lies upon the participating persons in order to save bit-rate in less interesting parts of the video. A Viola-Jones face detector will be used to detect the regions of interest. Once a(More)
A novel method for generating a reliable initial surface mesh of the interested scene from a quasi-dense point cloud is presented in this article. Given multiple images taken from different points of view, a robust quasi-dense point cloud is acquired by accumulative triangulation of the potentially matched feature points. In our proposed method, the feature(More)
Considering the growing amount of digital images in all kind of databases, the search for specific content remains a problem. Content-based image retrieval based on local features is a promising approach but comes with the problem of being memory and computational intensive. The bag of keypoints approach reduces the feature vectors to one histogramm per(More)
Fisher Vectors have shown great capability for visual search. Their main drawback is their high dimensionality. We propose several methods to reduce the size of the Fisher Vectors by applying different preprocessing steps and dimension reduction techniques to SIFT descriptors. Also, we investigate the effects of PCA and DCT transforms employed on SIFT(More)
In this paper we present a method for the detection of wrong feature correspondences in a local feature based object detection system. Common visual objects in different images share not only similar local features but also a similar spatial layout of their features. We will utilize this fact in order to distinguish between correct and wrong feature(More)