StorymapperArrow/MapArrow.js

mapboxgl.accessToken = 'pk.eyJ1Ijoib3V0ZG9vcm1hcHBpbmdjb21wYW55IiwiYSI6ImNqYmh3cDdjYzNsMnozNGxsYzlvMmk2bTYifQ.QqcZ4LVoLWnXafXdjZxnZg';
    const map = new mapboxgl.Map({
        container: 'map',
        center: [10, 50],
        zoom: 5
    });

import * as turf from "@turf/turf";
import { ARROW_BODY_STYLE_CONSTANT, ARROW_BODY_STYLE_LINEAR, ARROW_BODY_STYLE_EXPONENTIAL } from "./Arrow.js";

map.on('load', () => {
    const points = [
        [1.42076, 40.08804],
        [358.4050, 50.52]
    ];

    const fullPolygon = getArrowPolygon(points, 20000); // offset 20 km
    map.addSource("arrow-shape", { type: "geojson", data: fullPolygon });
    map.addLayer({
        id: "arrow-shape",
        type: "fill",
        source: "arrow-shape",
        paint: {
            "fill-color": "#ff0000",
            "fill-opacity": 0.7
        }
    });

    const grid = generateLatLonGrid(10);
    map.addSource("latLonGrid", { type: "geojson", data: grid });
    map.addLayer({
        id: "latLonGrid",
        type: "line",
        source: "latLonGrid",
        paint: {
            "line-color": "#888",
            "line-width": 1,
            "line-opacity": 0.5
        }
    });
    
    // Obrys (černý)
    map.addLayer({
        id: "arrow-outline",
        type: "line",
        source: "arrow-shape",
        paint: {
            "line-color": "#000000",
            "line-width": 2,
            "line-opacity": 1
        }
    });
});

const points = [
    { x: 70, y: 38 },
    { x: 71, y: 45},
    { x: 65, y: 50 },
    { x: 70, y: 53}
];

const arrowData = {
    points: points,
    splineStep: 0.01,
    spacing: 0.01,
    offsetDistance: 10000
  };
  const style = {
    calculation: ARROW_BODY_STYLE_LINEAR,
    range: 1,
    minValue: 0.1
  };
  const arrowHeadData = {
    widthArrow: 1,
    lengthArrow: 1
  };

// Cubic interpolation source from https://www.paulinternet.nl/?page=bicubic
function cubicInterpolate(p, x) {
    return p[1] + 0.5 * x * (p[2] - p[0] + x * (2.0 * p[0] - 5.0 * p[1] + 4.0 * p[2] - p[3] + x * (3.0 * (p[1] - p[2]) + p[3] - p[0])));
}

/**
 * @param {Object} arrowData - Object with data for arrow
 * @param {{x: number, y: number}[]} arrowData.points - List of points defining the arrow's path.
 * @param {number} arrowData.splineStep - The step size for the spline interpolation.
 * @param {number} arrowData.spacing - The spacing between the points along the arrow.
 * @param {number} arrowData.offsetDistance - The offset distance for the arrow's path (width).
 * 
 * @param {Object} style - Object with data for the calculation style.
 * @param {number} style.calculation - The style for the calculation
 * @param {number} style.range - The range for the calculation style.
 * @param {number} style.minValue - The minimum value used in the calculation.
 * 
 * @param {Object|undefined} arrowHeadData - Optional data for the arrowhead.
 * @param {number} arrowHeadData.widthArrow - The width of the arrowhead.
 * @param {number} arrowHeadData.lengthArrow - The length of the arrowhead.
 * 
 * @returns {{x: number, y: number}[]} - An array of points representing the arrow polygon.
 */
export function getArrowPolygon(arrowData, style= undefined, arrowHeadData = undefined) {
    const splineStep = 20;
    const smooth = computeSplinePoints(arrowData.points, splineStep);
    const { leftSidePoints, rightSidePoints } = computeSideOffsets(smooth, arrowData.offsetDistance);

    const end = smooth[smooth.length -1];
    const bearing = averageBearing(smooth, 3);
    const triangle = createIsoscelesTriangleCoords(turf.point(end), arrowData.offsetDistance * 5, arrowData.offsetDistance * 5, bearing);

    const polygonCoords = [
        ...leftSidePoints,
        ...triangle,
        ...rightSidePoints.reverse(),
        leftSidePoints[0]
    ];

    return turf.polygon([[...polygonCoords]]);
}

function averageBearing(points, count = 3) {
    const bearings = [];
    for (let i = points.length - count; i < points.length -1; i++) {
        if (i >= 0) {
            const b = turf.bearing(turf.point(points[i]), turf.point(points[i + 1]));
            bearings.push(b);
        }
    }
    // Průměr s korekcí kruhového rozsahu
    const sinSum = bearings.reduce((sum, b) => sum + Math.sin(b * Math.PI / 180), 0);
    const cosSum = bearings.reduce((sum, b) => sum + Math.cos(b * Math.PI / 180), 0);
    return Math.atan2(sinSum, cosSum) * 180 / Math.PI;
}

function computeSplinePoints(points, segments = 10) {
    if (points.length < 2) return points;
    const result = [];

    for (let i = 0; i < points.length - 1; i++) {
        const p0 = points[i === 0 ? i : i - 1];
        const p1 = points[i];
        const p2 = points[i + 1];
        const p3 = points[i + 2] || p2;
        for (let j = 0; j < segments; j++) {
            const t = j / segments;
           const lon = cubicInterpolate([p0[0], p1[0], p2[0], p3[0]], t);
            const lat = cubicInterpolate([p0[1], p1[1], p2[1], p3[1]], t);
            result.push([lon, lat]);
        }
    }

    result.push(points[points.length - 1]);
    return result;
}

function computeSideOffsets(points, offsetMeters) {
    let leftSidePoints = [];
    let rightSidePoints = [];

    for (let i = 1; i < points.length; i++) {
        const previousPoint = points[i - 1];
        const currentPoint = points[i];
        const bearing = turf.bearing(turf.point(previousPoint), turf.point(currentPoint));
        leftSidePoints.push(turf.destination(turf.point(currentPoint), offsetMeters, bearing - 90, { units: 'meters' }).geometry.coordinates);
        rightSidePoints.push(turf.destination(turf.point(currentPoint), offsetMeters, bearing + 90, { units: 'meters' }).geometry.coordinates);
    }

    return { leftSidePoints, rightSidePoints };
}

function createIsoscelesTriangleCoords(center, baseLengthMeters, heightMeters, bearing = 0) {
    const halfBase = baseLengthMeters / 2;
    const left = turf.destination(center, halfBase, bearing - 90, { units: 'meters' }).geometry.coordinates;
    const right = turf.destination(center, halfBase, bearing + 90, { units: 'meters' }).geometry.coordinates;
    const tip = turf.destination(center, heightMeters, bearing, { units: 'meters' }).geometry.coordinates;
    return [left, tip, right];
}

function generateLatLonGrid(step = 10) {
    const features = [];

    for (let lat = -80; lat <= 80; lat += step) {
        features.push({
            type: "Feature",
            geometry: {
                type: "LineString",
                coordinates: Array.from({ length: 37 }, (_, i) => [-180 + i * 10, lat])
            }
        });
    }

    for (let lon = -180; lon <= 180; lon += step) {
        features.push({
            type: "Feature",
            geometry: {
                type: "LineString",
                coordinates: Array.from({ length: 17 }, (_, i) => [lon, -80 + i * 10])
            }
        });
    }

    return {
        type: "FeatureCollection",
        features
    };
}