1. A method, performed by a computer, of rendering a stroked curved path having a fill thickness, the method comprising: forming, by the computer, a plurality of projection lines projecting from each side of the curved path, each of the projection lines having a length based on the fill thickness; determining, by the computer, intersection points for a plurality of intersecting consecutive projection lines located on a concave side of the curve; forming, by the computer, at least one extension polygon based on the intersection points and end points of the plurality of intersecting consecutive projection lines; forming, by the computer, a main polygon based on end points of the plurality of projection lines, and the intersection points, excluding at least one of the end points of a non-end cap projection line of the intersecting consecutive projection lines; and rendering, by the computer, the curved path using the at least one extension polygon and the main polygon.