google-map-react/src/lib/index.js at develop · bkocoglu/google-map-react · GitHub

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import log2 from '../utils/log2';

const GOOGLE_TILE_SIZE = 256;

function latLng2World({ lat, lng }) {

const sin = Math.sin((lat * Math.PI) / 180);

const x = lng / 360 + 0.5;

let y = 0.5 - (0.25 * Math.log((1 + sin) / (1 - sin))) / Math.PI;

y = y < 0 // eslint-disable-line

? 0

: y > 1

? 1

: y;

return { x, y };

}

function world2LatLng({ x, y }) {

const n = Math.PI - 2 * Math.PI * y;

// TODO test that this is faster

// 360 * Math.atan(Math.exp((180 - y * 360) * Math.PI / 180)) / Math.PI - 90;

return {

lat: (180 / Math.PI) * Math.atan(0.5 * (Math.exp(n) - Math.exp(-n))),

lng: x * 360 - 180,

};

}

// Thank you wiki https://en.wikipedia.org/wiki/Geographic_coordinate_system

function latLng2MetersPerDegree({ lat }) {

const phi = (lat * Math.PI) / 180;

const metersPerLatDegree =

111132.92 -

559.82 * Math.cos(2 * phi) +

1.175 * Math.cos(4 * phi) -

0.0023 * Math.cos(6 * phi);

const metersPerLngDegree =

111412.84 * Math.cos(phi) -

93.5 * Math.cos(3 * phi) +

0.118 * Math.cos(5 * phi);

return { metersPerLatDegree, metersPerLngDegree };

}

function meters2LatLngBounds(meters, { lat, lng }) {

const { metersPerLatDegree, metersPerLngDegree } = latLng2MetersPerDegree({

lat,

});

const latDelta = (0.5 * meters) / metersPerLatDegree;

const lngDelta = (0.5 * meters) / metersPerLngDegree;

return {

nw: {

lat: lat - latDelta,

lng: lng - lngDelta,

se: {

lat: lat + latDelta,

lng: lng + lngDelta,

};

}

function meters2WorldSize(meters, { lat, lng }) {

const { nw, se } = meters2LatLngBounds(meters, { lat, lng });

const nwWorld = latLng2World(nw);

const seWorld = latLng2World(se);

const w = Math.abs(seWorld.x - nwWorld.x);

const h = Math.abs(seWorld.y - nwWorld.y);

return { w, h };

}

function fitNwSe(nw, se, width, height) {

const EPS = 0.000000001;

const nwWorld = latLng2World(nw);

const seWorld = latLng2World(se);

const dx =

nwWorld.x < seWorld.x ? seWorld.x - nwWorld.x : 1 - nwWorld.x + seWorld.x;

const dy = seWorld.y - nwWorld.y;

if (dx <= 0 && dy <= 0) {

return null;

}

const zoomX = log2(width / GOOGLE_TILE_SIZE / Math.abs(dx));

const zoomY = log2(height / GOOGLE_TILE_SIZE / Math.abs(dy));

const zoom = Math.floor(EPS + Math.min(zoomX, zoomY));

// TODO find center just unproject middle world point

const middle = {

x: nwWorld.x < seWorld.x // eslint-disable-line

? 0.5 * (nwWorld.x + seWorld.x)

: nwWorld.x + seWorld.x - 1 > 0

? 0.5 * (nwWorld.x + seWorld.x - 1)

: 0.5 * (1 + nwWorld.x + seWorld.x),

y: 0.5 * (nwWorld.y + seWorld.y),

};

const scale = Math.pow(2, zoom);

const halfW = width / scale / GOOGLE_TILE_SIZE / 2;

const halfH = height / scale / GOOGLE_TILE_SIZE / 2;

const newNW = world2LatLng({

x: middle.x - halfW,

y: middle.y - halfH,

});

const newSE = world2LatLng({

x: middle.x + halfW,

y: middle.y + halfH,

});

return {

center: world2LatLng(middle),

zoom,

newBounds: {

nw: newNW,

se: newSE,

};

}

export function convertNeSwToNwSe({ ne, sw }) {

return {

nw: {

lat: ne.lat,

lng: sw.lng,

se: {

lat: sw.lat,

lng: ne.lng,

};

}

export function convertNwSeToNeSw({ nw, se }) {

return {

ne: {

lat: nw.lat,

lng: se.lng,

sw: {

lat: se.lat,

lng: nw.lng,

};

}

export function fitBounds({ nw, se, ne, sw }, { width, height }) {

let fittedData;

if (nw && se) {

fittedData = fitNwSe(nw, se, width, height);

} else {

const calculatedNwSe = convertNeSwToNwSe({ ne, sw });

fittedData = fitNwSe(calculatedNwSe.nw, calculatedNwSe.se, width, height);

}

return {

...fittedData,

newBounds: {

...fittedData.newBounds,

...convertNwSeToNeSw(fittedData.newBounds),

};

}

// -------------------------------------------------------------------

// Helpers to calc some markers size

export function meters2ScreenPixels(meters, { lat, lng }, zoom) {

const { w, h } = meters2WorldSize(meters, { lat, lng });

const scale = Math.pow(2, zoom);

const wScreen = w * scale * GOOGLE_TILE_SIZE;

const hScreen = h * scale * GOOGLE_TILE_SIZE;

return {

w: wScreen,

h: hScreen,

};

}

// --------------------------------------------------

// Helper functions for working with svg tiles, (examples coming soon)

export function tile2LatLng({ x, y }, zoom) {

const n = Math.PI - (2 * Math.PI * y) / Math.pow(2, zoom);

return {

lat: (180 / Math.PI) * Math.atan(0.5 * (Math.exp(n) - Math.exp(-n))),

lng: (x / Math.pow(2, zoom)) * 360 - 180,

};

}

export function latLng2Tile({ lat, lng }, zoom) {

const worldCoords = latLng2World({ lat, lng });

const scale = Math.pow(2, zoom);

return {

x: Math.floor(worldCoords.x * scale),

y: Math.floor(worldCoords.y * scale),

};

}

export function getTilesIds({ from, to }, zoom) {

const scale = Math.pow(2, zoom);

const ids = [];

for (let x = from.x; x !== (to.x + 1) % scale; x = (x + 1) % scale) {

for (let y = from.y; y !== (to.y + 1) % scale; y = (y + 1) % scale) {

ids.push([zoom, x, y]);

}

return ids;

}

google-map-react/src/lib/index.js at develop · bkocoglu/google-map-react · GitHub

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