1. A method for subtracting a background comprising: locating key points on an image of a known object type; determining line segments between the key points; locating boundary points of the image that comprise edges of the known object by using the line segments; eliminating pixel gaps between the boundary points; connecting the boundary points to obtain a closed loop of pixels; processing the edges to provide a clean-edged extraction of the image from a background image, including using an alpha image to determine a key point, which is selected based on a similarity score for a region in the alpha image; and reducing noise from the edges of the known object, after determining the key points, using an edge strength, the alpha image, and the line segments by aligning a snake to the line segments; wherein at least one key point is located based at least in part on a key point template comprising a plurality of pixels and specially configured for that key point; and wherein the pixels in the specially configured key point template that make up a shape associated with the key point have a first value and the other pixels in the specially configured key point template have a second value.