//function kindly provided by phrogz at: // var CP = window.CanvasRenderingContext2D && CanvasRenderingContext2D.prototype; if (CP && CP.lineTo) { CP.dashedLine = function (x, y, x2, y2, dashArray) { if (!dashArray) dashArray = [10, 5];//虚线长度，虚线间隔 var dashCount = dashArray.length; this.moveTo(x, y); var dx = (x2 - x), dy = (y2 - y); var slope = dy / dx; var distRemaining = Math.sqrt(dx * dx + dy * dy); var dashIndex = 0, draw = true; while (distRemaining >= 0.1) { var dashLength = dashArray[dashIndex++ % dashCount]; if (dashLength > distRemaining) dashLength = distRemaining; var xStep = Math.sqrt(dashLength * dashLength / (1 + slope * slope)); var signal = (x2 > x ? 1 : -1); x += xStep * signal; y += slope * xStep * signal; this[draw ? \'lineTo\' : \'moveTo\'](x, y); distRemaining -= dashLength; draw = !draw; } } }