Kanade, T.

Shape and motion from image streams under orthography: A factorization method


Inferring scene geometry and camera motion from a stream of images is possible in principle, but is an ill-conditioned problem when the objects are distant with respect to their size. An image stream can be represented by the 2F P measurement matrix of the image coordinates of P points tracked through F frames. Based on this observation, the factorization method uses the singular-value decomposition technique to factor the measurement matrix into two matrices which represent object shape and camera rotation respectively. The method can also handle and obtain a full solution from a partially filled-in measurement matrix that may result from occlusions or tracking failures.

Region segmentation: Signal vs semantics


The problem of region segmentation includes issues varying from the preprocessing of the image to its semantic interpretation. We first briefly present a model of image understanding to provide a paradigm in which the problem of region segmentation can be discussed. The model enables us to identify three levels of knowledge--signal, physical, and semantic--which play different roles in achieving the goals of region segmentation. This paper emphasizes the importance of exploiting the physical level of knowledge, the bridge between a picture and a scene.