let begin = [252, 0, 255];
let end = [0, 219, 222];
let rgbArr = [];
let length = this.geojsons.length;
let r = begin[0] - ((begin[0] - end[0]) * data.rownum) / length;
let g = begin[1] - ((begin[1] - end[1]) * data.rownum) / length;
let b = begin[2] - ((begin[2] - end[2]) * data.rownum) / length;
let rgb = "rgb(" + r + "," + g + "," + b + ")";
data.rownum 指当前元素的位置