1. A computer implemented method for identifying spam in an image, comprising: identifying one or more objects in the image, including text and graphic objects; tracing contours of one or more identified objects; computing angles of inclination of tangents at plurality of points on an object contour; determining, based on the angles of inclination, one or more attributes of the object contour, including lengths of line segments of the contour, angles between line segments the contour, lengths of arcs of the contour and radii of curvature of the arcs of the contour; generating object signatures containing one or more attributes of the object contours; comparing signatures of one or more objects of the image with known spam signatures; determining that the image contains spam if the number of object signatures that are substantially similar to the known spam signatures exceeds a predetermined threshold.