OGC vector tile source
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Tim Schaub
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/**
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* @module ol/source/ogcTileUtil
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*/
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import TileGrid from '../tilegrid/TileGrid.js';
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import {assign} from '../obj.js';
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import {getJSON, resolveUrl} from '../net.js';
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import {get as getProjection} from '../proj.js';
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/**
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* See https://ogcapi.ogc.org/tiles/.
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*/
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/**
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* @enum {string}
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*/
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const TileType = {
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MAP: 'map',
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VECTOR: 'vector',
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};
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/**
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* @typedef {Object} TileSet
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* @property {TileType} dataType Type of data represented in the tileset.
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* @property {string} [tileMatrixSetDefinition] Reference to a tile matrix set definition.
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* @property {TileMatrixSet} [tileMatrixSet] Tile matrix set definition.
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* @property {Array<TileMatrixSetLimits>} [tileMatrixSetLimits] Tile matrix set limits.
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* @property {Array<Link>} links Tileset links.
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*/
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/**
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* @typedef {Object} Link
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* @property {string} rel The link rel attribute.
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* @property {string} href The link URL.
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* @property {string} type The link type.
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*/
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/**
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* @typedef {Object} TileMatrixSetLimits
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* @property {string} tileMatrix The tile matrix id.
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* @property {number} minTileRow The minimum tile row.
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* @property {number} maxTileRow The maximum tile row.
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* @property {number} minTileCol The minimum tile column.
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* @property {number} maxTileCol The maximum tile column.
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*/
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/**
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* @typedef {Object} TileMatrixSet
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* @property {string} id The tile matrix set identifier.
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* @property {string} crs The coordinate reference system.
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* @property {Array<TileMatrix>} tileMatrices Array of tile matrices.
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*/
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/**
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* @typedef {Object} TileMatrix
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* @property {string} id The tile matrix identifier.
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* @property {number} cellSize The pixel resolution (map units per pixel).
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* @property {Array<number>} pointOfOrigin The map location of the matrix origin.
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* @property {string} [cornerOfOrigin='topLeft'] The corner of the matrix that represents the origin ('topLeft' or 'bottomLeft').
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* @property {number} matrixWidth The number of columns.
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* @property {number} matrixHeight The number of rows.
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* @property {number} tileWidth The pixel width of a tile.
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* @property {number} tileHeight The pixel height of a tile.
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*/
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/**
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* @type {Object<string, boolean>}
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*/
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const knownMapMediaTypes = {
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'image/png': true,
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'image/jpeg': true,
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'image/gif': true,
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'image/webp': true,
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};
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/**
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* @type {Object<string, boolean>}
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*/
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const knownVectorMediaTypes = {
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'application/vnd.mapbox-vector-tile': true,
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'application/geo+json': true,
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};
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/**
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* @typedef {Object} TileSetInfo
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* @property {string} urlTemplate The tile URL template.
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* @property {import("../tilegrid/TileGrid.js").default} grid The tile grid.
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* @property {import("../Tile.js").UrlFunction} urlFunction The tile URL function.
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*/
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/**
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* @typedef {Object} SourceInfo
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* @property {string} url The tile set URL.
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* @property {string} mediaType The preferred tile media type.
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* @property {import("../proj/Projection.js").default} projection The source projection.
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* @property {Object} [context] Optional context for constructing the URL.
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*/
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const BOTTOM_LEFT_ORIGIN = 'bottomLeft';
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/**
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* @param {Array<Link>} links Tileset links.
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* @param {string} [mediaType] The preferred media type.
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* @return {string} The tile URL template.
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*/
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export function getMapTileUrlTemplate(links, mediaType) {
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let tileUrlTemplate;
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let fallbackUrlTemplate;
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for (let i = 0; i < links.length; ++i) {
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const link = links[i];
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if (link.rel === 'item') {
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if (link.type === mediaType) {
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tileUrlTemplate = link.href;
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break;
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}
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if (knownMapMediaTypes[link.type]) {
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fallbackUrlTemplate = link.href;
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} else if (!fallbackUrlTemplate && link.type.indexOf('image/') === 0) {
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fallbackUrlTemplate = link.href;
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}
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}
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}
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if (!tileUrlTemplate) {
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if (fallbackUrlTemplate) {
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tileUrlTemplate = fallbackUrlTemplate;
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} else {
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throw new Error('Could not find "item" link');
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}
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}
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return tileUrlTemplate;
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}
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/**
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* @param {Array<Link>} links Tileset links.
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* @param {string} [mediaType] The preferred media type.
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* @return {string} The tile URL template.
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*/
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export function getVectorTileUrlTemplate(links, mediaType) {
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let tileUrlTemplate;
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let fallbackUrlTemplate;
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for (let i = 0; i < links.length; ++i) {
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const link = links[i];
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if (link.rel === 'item') {
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if (link.type === mediaType) {
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tileUrlTemplate = link.href;
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break;
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}
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if (knownVectorMediaTypes[link.type]) {
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fallbackUrlTemplate = link.href;
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}
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}
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}
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if (!tileUrlTemplate) {
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if (fallbackUrlTemplate) {
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tileUrlTemplate = fallbackUrlTemplate;
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} else {
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throw new Error('Could not find "item" link');
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}
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}
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return tileUrlTemplate;
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}
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/**
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* @param {SourceInfo} sourceInfo Source info.
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* @return {Promise<TileSetInfo>} Tile set info.
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*/
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export function getTileSetInfo(sourceInfo) {
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let tileUrlTemplate;
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/**
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* @param {TileMatrixSet} tileMatrixSet Tile matrix set.
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* @return {TileSetInfo} Tile set info.
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*/
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function parseTileMatrixSet(tileMatrixSet) {
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let projection = sourceInfo.projection;
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if (!projection) {
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projection = getProjection(tileMatrixSet.crs);
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if (!projection) {
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throw new Error(`Unsupported CRS: ${tileMatrixSet.crs}`);
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}
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}
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const backwards = projection.getAxisOrientation().substr(0, 2) !== 'en';
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// TODO: deal with limits
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const matrices = tileMatrixSet.tileMatrices;
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const length = matrices.length;
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const origins = new Array(length);
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const resolutions = new Array(length);
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const sizes = new Array(length);
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const tileSizes = new Array(length);
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for (let i = 0; i < matrices.length; ++i) {
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const matrix = matrices[i];
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const origin = matrix.pointOfOrigin;
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if (backwards) {
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origins[i] = [origin[1], origin[0]];
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} else {
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origins[i] = origin;
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}
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resolutions[i] = matrix.cellSize;
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sizes[i] = [matrix.matrixWidth, matrix.matrixHeight];
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tileSizes[i] = [matrix.tileWidth, matrix.tileHeight];
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}
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const tileGrid = new TileGrid({
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origins: origins,
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resolutions: resolutions,
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sizes: sizes,
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tileSizes: tileSizes,
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});
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const context = sourceInfo.context;
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const base = sourceInfo.url;
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function tileUrlFunction(tileCoord, pixelRatio, projection) {
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if (!tileCoord) {
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return undefined;
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}
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const matrix = matrices[tileCoord[0]];
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const upsideDown = matrix.cornerOfOrigin === BOTTOM_LEFT_ORIGIN;
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const localContext = {
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tileMatrix: matrix.id,
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tileCol: tileCoord[1],
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tileRow: upsideDown ? -tileCoord[2] - 1 : tileCoord[2],
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};
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assign(localContext, context);
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const url = tileUrlTemplate.replace(/\{(\w+?)\}/g, function (m, p) {
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return localContext[p];
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});
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return resolveUrl(base, url);
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}
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return {
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grid: tileGrid,
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urlTemplate: tileUrlTemplate,
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urlFunction: tileUrlFunction,
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};
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}
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/**
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* @param {TileSet} tileSet Tile set.
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* @return {TileSetInfo|Promise<TileSetInfo>} Tile set info.
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*/
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function parseTileSetMetadata(tileSet) {
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if (tileSet.dataType === TileType.MAP) {
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tileUrlTemplate = getMapTileUrlTemplate(
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tileSet.links,
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sourceInfo.mediaType
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);
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} else if (tileSet.dataType === TileType.VECTOR) {
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tileUrlTemplate = getVectorTileUrlTemplate(
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tileSet.links,
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sourceInfo.mediaType
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);
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} else {
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throw new Error('Expected tileset data type to be "map" or "vector"');
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}
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if (tileSet.tileMatrixSet) {
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return parseTileMatrixSet(tileSet.tileMatrixSet);
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}
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if (!tileSet.tileMatrixSetDefinition) {
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throw new Error('Expected tileMatrixSetDefinition or tileMatrixSet');
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}
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const url = resolveUrl(sourceInfo.url, tileSet.tileMatrixSetDefinition);
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return getJSON(url).then(parseTileMatrixSet);
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}
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return getJSON(sourceInfo.url).then(parseTileSetMetadata);
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}
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