function getColorStopValues(visualMapModel, valueState, dataExtent) {
	        if (dataExtent[0] === dataExtent[1]) {
	            return dataExtent.slice();
	        }

	        // When using colorHue mapping, it is not linear color any more.
	        // Moreover, canvas gradient seems not to be accurate linear.
	        // FIXME
	        // Should be arbitrary value 100? or based on pixel size?
	        var count = 200;
	        var step = (dataExtent[1] - dataExtent[0]) / count;

	        var value = dataExtent[0];
	        var stopValues = [];
	        for (var i = 0; i <= count && value < dataExtent[1]; i++) {
	            stopValues.push(value);
	            value += step;
	        }
	        stopValues.push(dataExtent[1]);

	        return stopValues;
	    }
@public
@param {module:echarts/data/List} list
@return {string} Concrete dimention. If return null/undefined,
                 no dimension used.