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@mapbox/mapbox-gl-style-spec

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a specification for mapbox gl styles

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import quickselect from 'quickselect'; import Point from '@mapbox/point-geometry'; type Ring = Point[] & {area?: number}; // minX, minY, maxX, maxY export type BBox = [number, number, number, number]; /** * Returns the signed area for the polygon ring. Postive areas are exterior rings and * have a clockwise winding. Negative areas are interior rings and have a counter clockwise * ordering. */ function calculateSignedArea(ring: Ring): number { let sum = 0; for (let i = 0, len = ring.length, j = len - 1, p1, p2; i < len; j = i++) { p1 = ring[i]; p2 = ring[j]; sum += (p2.x - p1.x) * (p1.y + p2.y); } return sum; } function compareAreas(a: Ring, b: Ring): number { return b.area - a.area; } // classifies an array of rings into polygons with outer rings and holes export function classifyRings(rings: Array<Ring>, maxRings: number): Array<Array<Ring>> { const len = rings.length; if (len <= 1) return [rings]; const polygons = []; let polygon, ccw; for (let i = 0; i < len; i++) { const area = calculateSignedArea(rings[i]); if (area === 0) continue; rings[i].area = Math.abs(area); if (ccw === undefined) ccw = area < 0; if (ccw === area < 0) { if (polygon) polygons.push(polygon); polygon = [rings[i]]; } else { (polygon).push(rings[i]); } } if (polygon) polygons.push(polygon); // Earcut performance degrades with the # of rings in a polygon. For this // reason, we limit strip out all but the `maxRings` largest rings. if (maxRings > 1) { for (let j = 0; j < polygons.length; j++) { if (polygons[j].length <= maxRings) continue; quickselect(polygons[j], maxRings, 1, polygons[j].length - 1, compareAreas); polygons[j] = polygons[j].slice(0, maxRings); } } // eslint-disable-next-line @typescript-eslint/no-unsafe-return return polygons; } export function updateBBox(bbox: BBox, coord: GeoJSON.Position) { bbox[0] = Math.min(bbox[0], coord[0]); bbox[1] = Math.min(bbox[1], coord[1]); bbox[2] = Math.max(bbox[2], coord[0]); bbox[3] = Math.max(bbox[3], coord[1]); } export function boxWithinBox(bbox1: BBox, bbox2: BBox): boolean { if (bbox1[0] <= bbox2[0]) return false; if (bbox1[2] >= bbox2[2]) return false; if (bbox1[1] <= bbox2[1]) return false; if (bbox1[3] >= bbox2[3]) return false; return true; } function onBoundary(p: GeoJSON.Position, p1: GeoJSON.Position, p2: GeoJSON.Position) { const x1 = p[0] - p1[0]; const y1 = p[1] - p1[1]; const x2 = p[0] - p2[0]; const y2 = p[1] - p2[1]; return (x1 * y2 - x2 * y1 === 0) && (x1 * x2 <= 0) && (y1 * y2 <= 0); } function rayIntersect(p: GeoJSON.Position, p1: GeoJSON.Position, p2: GeoJSON.Position) { return ((p1[1] > p[1]) !== (p2[1] > p[1])) && (p[0] < (p2[0] - p1[0]) * (p[1] - p1[1]) / (p2[1] - p1[1]) + p1[0]); } // ray casting algorithm for detecting if point is in polygon export function pointWithinPolygon( point: GeoJSON.Position, rings: Array<Array<GeoJSON.Position>>, trueOnBoundary: boolean = false, ): boolean { let inside = false; for (let i = 0, len = rings.length; i < len; i++) { const ring = rings[i]; for (let j = 0, len2 = ring.length, k = len2 - 1; j < len2; k = j++) { const q1 = ring[k]; const q2 = ring[j]; if (onBoundary(point, q1, q2)) return trueOnBoundary; if (rayIntersect(point, q1, q2)) inside = !inside; } } return inside; } function perp(v1: GeoJSON.Position, v2: GeoJSON.Position) { return v1[0] * v2[1] - v1[1] * v2[0]; } // check if p1 and p2 are in different sides of line segment q1->q2 function twoSided(p1: GeoJSON.Position, p2: GeoJSON.Position, q1: GeoJSON.Position, q2: GeoJSON.Position) { // q1->p1 (x1, y1), q1->p2 (x2, y2), q1->q2 (x3, y3) const x1 = p1[0] - q1[0]; const y1 = p1[1] - q1[1]; const x2 = p2[0] - q1[0]; const y2 = p2[1] - q1[1]; const x3 = q2[0] - q1[0]; const y3 = q2[1] - q1[1]; const det1 = x1 * y3 - x3 * y1; const det2 = x2 * y3 - x3 * y2; if ((det1 > 0 && det2 < 0) || (det1 < 0 && det2 > 0)) return true; return false; } // a, b are end points for line segment1, c and d are end points for line segment2 export function segmentIntersectSegment( a: GeoJSON.Position, b: GeoJSON.Position, c: GeoJSON.Position, d: GeoJSON.Position, ): boolean { // check if two segments are parallel or not // precondition is end point a, b is inside polygon, if line a->b is // parallel to polygon edge c->d, then a->b won't intersect with c->d const vectorP = [b[0] - a[0], b[1] - a[1]]; const vectorQ = [d[0] - c[0], d[1] - c[1]]; if (perp(vectorQ, vectorP) === 0) return false; // If lines are intersecting with each other, the relative location should be: // a and b lie in different sides of segment c->d // c and d lie in different sides of segment a->b if (twoSided(a, b, c, d) && twoSided(c, d, a, b)) return true; return false; } export interface Bounds { min: Point; max: Point; } export function computeBounds(points: Point[][]): Bounds { const min = new Point(Number.POSITIVE_INFINITY, Number.POSITIVE_INFINITY); const max = new Point(Number.NEGATIVE_INFINITY, Number.NEGATIVE_INFINITY); for (const point of points[0]) { if (min.x > point.x) min.x = point.x; if (min.y > point.y) min.y = point.y; if (max.x < point.x) max.x = point.x; if (max.y < point.y) max.y = point.y; } return {min, max}; }