function clampCssByte(i) {  // Clamp to integer 0 .. 255.
	        i = Math.round(i);  // Seems to be what Chrome does (vs truncation).
	        return i < 0 ? 0 : i > 255 ? 255 : i;
	    }
@param {string} colorStr
@param {Array.<number>} out
@return {Array.<number>}
@memberOf module:zrender/util/color