<html>
    <head>
	<script>
        function clip (subjectPolygon, clipPolygon) {

            var cp1, cp2, s, e;
            var inside = function (p) {
                return (cp2[0]-cp1[0])*(p[1]-cp1[1]) > (cp2[1]-cp1[1])*(p[0]-cp1[0]);
            };
            var intersection = function () {
                var dc = [ cp1[0] - cp2[0], cp1[1] - cp2[1] ],
                    dp = [ s[0] - e[0], s[1] - e[1] ],
                    n1 = cp1[0] * cp2[1] - cp1[1] * cp2[0],
                    n2 = s[0] * e[1] - s[1] * e[0], 
                    n3 = 1.0 / (dc[0] * dp[1] - dc[1] * dp[0]);
                return [(n1*dp[0] - n2*dc[0]) * n3, (n1*dp[1] - n2*dc[1]) * n3];
            };
            var outputList = subjectPolygon;
            cp1 = clipPolygon[clipPolygon.length-1];
            for (var j in clipPolygon) {
                cp2 = clipPolygon[j];
                var inputList = outputList;
                outputList = [];
                s = inputList[inputList.length - 1];