  var height = api.size([0, 1])[1] * 0.6;

                    var rectShape = echarts.graphic.clipRectByRect({
                        x: start[0],
                        y: start[1] - height / 2,
                        width: end[0] - start[0],
                        height: height
                    }, {
                        x: params.coordSys.x,
                        y: params.coordSys.y,
                        width: params.coordSys.width,
                        height: params.coordSys.heigh