int imagepolygon (int im, array points, int num_points, int col)
ImagePolygon() creates a polygon in image id. Points is a PHP array containing the polygon's vertices, ie. points[0] = x0, points[1] = y0, points[2] = x1, points[3] = y1, etc. Num_points is the total number of vertices.
See also imagecreate().