Feature extraction using the constrained gradient

Low-level operators are needed in most computer vision applications in order to get relevant image primitives. In this paper, we present a line and a comer detector. Both operators use specific constraints on the gradient of the image intensity. The operators are applied to satellite and aerial images. The line detector is very useful for extracting roads even on the noisy SAR images, while the comer detector enables to detect salient points such as comers of buildings in aerial images. The information brought by these detectors completes the edge-based description of an image.