1. A method comprising using at least one hardware processor for: applying an edge detection algorithm to an image of a document, to receive a map of edges from which multiple optional contours of the document in the image are identified; splitting the multiple optional contours into line segments; sorting the line segments into equivalence classes of collinearity representing distinct line segments of the line segments, wherein each one of the classes of collinearity represents a distinct line segment of the distinct line segments; deriving a connectivity graph based on the equivalence classes of collinearity; defining a central region in the image of the document; removing edge pixels of the edge map which are located within the central region; identifying four-vertex polygons in said connectivity graph; evaluating each one of the identified four-vertex polygons according to one or more segmentation criterions; and segmenting the document in the image according to the most highly evaluated four-vertex polygon of the four-vertex polygons.