Planar orientation from blur gradients in a single image

We present a focus-based method to recover the orientation of a textured planar surface patch from a single image. The method exploits the relationship between the orientation of equifocal (i.e. uniformly-blurred) contours in the image and the plane´s tilt and slant angles. Compared to previous methods that determine planar orientation, we make fewer assumptions about the texture and remove the restriction that images must be acquired through a pinhole aperture. Our method estimates slant and tilt of an image patch in a single image, as compared to depth from defocus methods that require two or more input images. Experiments are performed using a large set of test images.