在填充绘制路径时，getContext.fill()方法有两个参数，当为'evenodd'时，重叠的部分去掉，为啥在我这里不行，请问如何修改呢？<canvas id=c></canvas><script> var w = c.width = window.innerWidth, h = c.height = window.innerHeight, ctx = c.getContext('2d'), offset = 0; points = []; function smoothLine(points) { ctx.fillStyle="red"; ctx.fill('evenodd'); // 主要是这里； ctx.lineWidth = 3; ctx.strokeStyle = '#eee'; ctx.lineTo(points[points.length - 1].x, points[points.length - 1].y); ctx.setLineDash([5, 4, 3]); march(); ctx.lineDashOffset = offset; ctx.stroke(); } function march() { offset++; if (offset > 15) { offset = 0; } setTimeout(march, 20); } c.onmousedown = function (e) { points.push({x: e.clientX, y: e.clientY}); ctx.fill('evenodd'); c.onmousemove = function (e) { points.push({x: e.clientX, y: e.clientY}); smoothLine(points); }; c.onmouseup = function () { ctx.closePath() c.onmousemove = null; c.onmouseup = null; }; };</script>