src/Gisplay/Maps/ChangeMap.js

import { Map } from './Map';
import { Legend } from '../Legend';
import { Aesthetic } from '../Aesthetic';

/**
 * ChangeMap implementation 07/03
 */
export class ChangeMap extends Map {

    constructor(bgmap, geometry, options) {
        super(bgmap, geometry, options);
        this.geometry = geometry;
        this.aesthetics = new Array();
        this.attr = "change";
        this.loadOptions(options, bgmap);
        this.id = mapcount++;
        this.attr = "change";//@Rui Duplicate?
        this.type = 'CM';
        maps.push(this);
        this.initialize();

        /*  return this;*/
    }

    draw() {
        this.clear();
        for (let i = 0; i < this.aesthetics.length; i++) {
            if (this.aesthetics[i].enabled == true) {
                this.drawContinuousPolygons(this.aesthetics[i]);
            }
            this.drawBorders(this.aesthetics[i]);
        }
    }

    preProcessData(geojson, numberOf, algorithm, colorscheme) {
        const aesarray = [];
        const values = [];
        let breaks;
        //var fcolor;
        for (let g = 0; g < geojson.features.length && (this.maxfeatures == undefined || g < this.maxfeatures); g++) {
            if (typeof geojson.features[g].properties[this.minuend] == 'number' && geojson.features[g].properties[this.minuend] != null && typeof geojson.features[g].properties[this.subtrahend] == 'number' && geojson.features[g].properties[this.subtrahend] != null) {
                this.max = Math.max(this.max, geojson.features[g].properties[this.minuend] - geojson.features[g].properties[this.subtrahend]);
                this.min = Math.min(this.min, geojson.features[g].properties[this.minuend] - geojson.features[g].properties[this.subtrahend]);
            }
        }
        breaks = [this.min, this.max];
        this.fcolor = chroma.scale(colorscheme);
        const aes = new Aesthetic(0, this.attr, this.fcolor, [0, 0, 0, 1], null, [breaks[0], breaks[1]]);
        aes.outer = true;
        aesarray.push(aes);

        this.aesthetics = aesarray;
    }

    buildLegend() {
        this.legend = new Legend(this.id, this.legendTitle);
        this.legend.insertGradient(this, this.min, 0, this.max);
        this.legend.insertLegend(this.map);
    }

    defaults() {
        const options = {};
        return options;
    }
}