@pierstoval
Freelance PHP/Symfony dev & training consultant
A medieval world with horrific and gothic overtones
A table-top role-playing game
4 music albums
A board game (the Black Rose)
And more to come...
The genesis of a "map" application
Zones
Places
Routes
Crossroads
"start" marker
"end" marker
Baidu Maps ; Bing Maps ; Bhuvan ; Google Maps ; HERE WeGo ; Map World ; Mappy ; MapQuest ; Qwant Maps ; ViaMichelin ; WikiMapia ; etc.
OpenStreetMap ; OpenSeaMap
But...
🌍
These are all for the Earth... 😭
Okay, let's find a way to create a CUSTOM IMAGINARY map.
Well... Any database, but maybe PostgreSQL + PostGIS is the best for this purpose
The previously indicated tools are not the best options
(except Leaflet which is awesome)
Please use Mapnik + PostgreSQL + PostGIS + Leaflet.
Don't hurt yourself like I did.
Let's pick this one!
Most famous: Mercator projection
Solution for us:
bitmap-like
Awesome docs!
// Matches a #map selector
var containerId = 'map';
var map = L.map(containerId);
// This is for OpenStreetMap's default map layer
L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png').addTo(map);
// Add a marker on the map
var marker = L.marker([51.5, -0.09]).addTo(mymap);
// Add a polygon on the map
var polygon = L.polygon([[51.509, -0.08], [51.503, -0.06],[51.51, -0.047]]).addTo(mymap);
// Add a multipoint line on the map
var polyline = L.polyline([[51.509, -0.08], [51.51, -0.047]]).addTo(mymap);
By default, Leaflet uses Spherical Mercator projection, and uses mathematical rules to calculate distances & coordinates
L.CRS.EPSG3857 = Util.extend({}, Earth, {
code: 'EPSG:3857',
projection: SphericalMercator,
transformation: (function() {
var scale = 0.5 / (Math.PI * SphericalMercator.R);
return toTransformation(scale, 0.5, -scale, 0.5);
}())
});
export var SphericalMercator = {
R: 6378137,
MAX_LATITUDE: 85.0511287798,
project: function(latlng) {
var d = Math.PI / 180,
max = this.MAX_LATITUDE,
lat = Math.max(Math.min(max, latlng.lat), -max),
sin = Math.sin(lat * d);
return new Point(
this.R * latlng.lng * d,
this.R * Math.log((1 + sin) / (1 - sin)) / 2);
},
unproject: function(point) {
var d = 180 / Math.PI;
return new LatLng(
(2 * Math.atan(Math.exp(point.y / this.R)) - (Math.PI / 2)) * d,
point.x * d / this.R);
},
bounds: (function() {
var d = 6378137 * Math.PI;
return new Bounds([-d, -d], [d, d]);
})()
};
Simplify all the things!
L.CRS.XY = L.Util.extend({}, L.CRS.Simple, {
code: 'XY',
projection: L.Projection.LonLat,
transformation: new L.Transformation(1, 0, 1, 0)
});
This tells LeafletJS to calculate coordinates on an [x,y] simple 2D system
But that's not finished...
By default, LonLat projection (classic 2D) is still similar to Mercator in a point:
y = 0 is bottom
y = 10 is top
Let's reverse this!
L.LatLngBounds.prototype.extend = function (obj) {
if (!obj) { return this; }
var latLng = L.latLng(obj);
if (latLng !== null) {
obj = latLng;
} else {
obj = L.latLngBounds(obj);
}
if (obj instanceof L.LatLng) {
if (!this._southWest && !this._northEast) {
this._southWest = new L.LatLng(obj.lat, obj.lng);
this._northEast = new L.LatLng(obj.lat, obj.lng);
} else {
// Here we set "max" instead of "min" in the original code
this._southWest.lat = Math.max(obj.lat, this._southWest.lat);
this._southWest.lng = Math.min(obj.lng, this._southWest.lng);
// Here we set "min" instead of "max" in the original code
this._northEast.lat = Math.min(obj.lat, this._northEast.lat);
this._northEast.lng = Math.max(obj.lng, this._northEast.lng);
}
} else if (obj instanceof L.LatLngBounds) {
this.extend(obj._southWest);
this.extend(obj._northEast);
}
return this;
};
Only the 2 lines after each comment are custom.
The rest is copy/pasted from Leaflet.
Original map is 5433×4252 pixels wide.
I opted for 5 zoom levels.
With Leaflet, it's interpreted like this:
The higher the zoom, the more details you want on your map.
Equation to get the ratio for a given level:
Ratios for 5 zoom levels:
ImageMagick commands:
magick convert original_map.jpg
-background "#000000" -extent "5433x5433" -resize "3.125%" -crop 168x168
-background "#000000" -extent "168x168" -thumbnail "168x168" "output/$MAP_ID/0.jpg"
magick convert original_map.jpg
-background "#000000" -extent "5433x5433" -resize "6.25%" -crop 168x168
-background "#000000" -extent "168x168" -thumbnail "168x168" "output/$MAP_ID/1.jpg"
magick convert original_map.jpg
-background "#000000" -extent "5433x5433" -resize "12.5%" -crop 168x168
-background "#000000" -extent "168x168" -thumbnail "168x168" "output/$MAP_ID/2.jpg"
magick convert original_map.jpg
-background "#000000" -extent "5433x5433" -resize "25%" -crop 168x168
-background "#000000" -extent "168x168" -thumbnail "168x168" "output/$MAP_ID/3.jpg"
magick convert original_map.jpg
-background "#000000" -extent "5433x5433" -resize "50%" -crop 168x168
-background "#000000" -extent "168x168" -thumbnail "168x168" "output/$MAP_ID/4.jpg"
magick convert original_map.jpg
-background "#000000" -extent "5433x5433" -resize "100%" -crop 168x168
-background "#000000" -extent "168x168" -thumbnail "168x168" "output/$MAP_ID/5.jpg"
ImageMagick options "-extent", "-resize", "-thumbnail" and "-crop" need a "geometry" argument.
Sources:
I made a regex for that:
(?<size>(?<w>(?:\d*(?:\.\d+)?)?%?)?(?:x(?<h>(?:\d*(?:\.\d+)?)?%?))?)(?<aspect>[!><@^])?(?<offset>(?<x>[+-]\d*(?:\.\d+)?)?(?<y>[+-]\d*(?:\.\d+)?)?)
(and an additionnal validator for non-regex-related checks)
$ tree maps_tiles/$MAP_ID/
75 directories, 1498 files
ImageMagick output needs some sorting/renaming to be integrated in LeafletJS as a map tile layer.
And after that:
Want a glimpse of the rendering?
@pierstoval