Como no había respuestas a mis preguntas, traté de inspirarme en otro código ya existente, y seguí desarrollando un constructor GeoJSON básico en Openlayers 3, que llena mis necesidades.
En realidad puedo
- cargar diferentes capas de PostGIS pasando un nombre de tabla, campos de tabla y una cláusula WHERE (con toda la magia posible de PosgreSQL / PostGis)
- diseñarlos (usando valores únicos, únicos o de rango)
- mostrar / ocultar capas en min / maxResolution
- el identificador único debe ser id para evitar que las funciones se carguen varias veces
- las capas se cargan mediante la estrategia ol.loadingstrategy.bbox, por lo que solo se cargan datos visibles
- definir plantillas emergentes específicas de capa
- agregar etiquetado específico de capa
Por lo tanto, ya es un paquete divertido, que se puede adaptar (y mejorar) muy fácilmente. Por lo tanto, quiero compartir el código aquí. El conjunto consta de tres partes:
- ol3Vector.js una clase extendida de ol.layer.Vector
- un archivo map.js en el que se definen el mapa y todas las capas
- El archivo get_geojson.php que se usa en el servidor para construir la cadena sql y devolver GeoJSON válido.
Para que funcione correctamente, ol3Vector.js debe cargarse primero. Aquí está el código:
// class to load vector layers from Postgis using a modified php-script from
// Bryan McBride
// https://github.com/bmcbride/PHP-Database-GeoJSON
//
ol3Vector = function(options) {
//
// -------- Defining default style settings ----------
//
var fill = new ol.style.Fill({
color: 'rgba(255,255,255,0.4)'
});
var stroke = new ol.style.Stroke({
color: '#3399CC',
width: 1.25
});
var text = new ol.style.Text({
text: "",
font: "16px Calibri,sans-serif",
fill: new ol.style.Fill({
color: [255, 255, 255, 1]
}),
stroke: new ol.style.Stroke({
color: [0, 0, 0, 1],
width: 2.5
})
});
var image = new ol.style.Circle({ // actually point styling only works with image, and not with icons
fill: fill,
stroke: stroke,
radius: 5
});
var style = new ol.style.Style({
image: image,
fill: fill,
stroke: stroke,
text: text
});
var styles = [style];
//
// ------------- defining options to build the new ol3Vector-layer -----------
//
var options = {
title: options.title,
visible: false,
geotable: options.geotable, // table name in PostGis-database
fields: options.fields, // field-names
where: options.where, // where-string passed to PostGis
source: new ol.source.Vector({
projection: "EPSG:4326",
attributions: [new ol.Attribution({
html: options.attribution
})],
strategy: ol.loadingstrategy.bbox, //load only data off the visible map
loader: function(extent, resolution, projection) {
var extent = ol.proj.transformExtent(extent, projection.getCode(), ol.proj.get('EPSG:4326').getCode());
$.ajax({
type: "GET",
dataType: "json",
url: "./mapdata/get_geojson.php?" + // define path to the get_geojson.php script
"geotable=" + options.geotable +
"&fields=" + options.fields +
"&where=" + options.where +
"&bbox=" + extent.join(","),
context: this
}).done(function(data) {
var format = new ol.format.GeoJSON();
this.addFeatures(format.readFeatures(data, {
dataProjection: "EPSG:4326",
featureProjection: "EPSG:3857"
}));
});
}
}),
minResolution: options.minResolution,
maxResolution: options.maxResolution,
content: options.content,
symbology: options.symbology,
showLabels: options.showLabels,
label: options.label,
style: (function label_style() { // style function needed to be wrapped in a function to get it work
// ------ labeling -----------
var layerLabel = "";
if (!options.showLabels) {
layerLabel = "";
} else if (options.showLabels) {
layerLabel = options.label;
}
return function(feature, resolution) {
style.getText().setText(feature.get(layerLabel));
// ------ styling -------------
if (!options.symbology) {
return style;
// return false;
} else if (options.symbology) {
var atts = feature.getProperties();
switch (options.symbology.type) {
case "single":
// Its a single symbology for all features so just set the values for fill and stroke
//
switch (feature.getGeometry().getType()) {
case "Point":
case "MultiPoint":
style.image = style.getImage().getFill().setColor(options.symbology.styleOptions.fill);
style.image = style.getImage().getStroke().setColor(options.symbology.styleOptions.color);
style.image = style.getImage().getStroke().setWidth(options.symbology.styleOptions.width);
style.image = style.getImage().setRadius(options.symbology.styleOptions.radius);
break;
case "LineString":
case "MultiLineString":
case "Polygon":
case "MultiPolygon":
style.fill = style.setFill(new ol.style.Fill({
color: options.symbology.styleOptions.fill
}));
style.stroke = style.setStroke(new ol.style.Stroke({
color: options.symbology.styleOptions.color,
width: options.symbology.styleOptions.width
}));
break;
}
break;
case "unique":
// Its a unique symbology. Check if the features property value matches that in the symbology and style accordingly
//
var att = options.symbology.property;
for (var i = 0, len = options.symbology.values.length; i < len; i++) { // field with values to define styles
if (atts[att] == options.symbology.values[i].value) { // unique value to identify style
for (var key in options.symbology.values[i].styleOptions) {
switch (feature.getGeometry().getType()) {
case "Point":
case "MultiPoint":
style.image = style.getImage().getFill().setColor(options.symbology.values[i].styleOptions.fill);
style.image = style.getImage().getStroke().setColor(options.symbology.values[i].styleOptions.color);
style.image = style.getImage().getStroke().setWidth(options.symbology.values[i].styleOptions.width);
style.image = style.getImage().setRadius(options.symbology.values[i].styleOptions.radius);
break;
case "LineString":
case "MultiLineString":
case "Polygon":
case "MultiPolygon":
style.fill = style.setFill(new ol.style.Fill({
color: options.symbology.values[i].styleOptions.fill
}));
style.stroke = style.setStroke(new ol.style.Stroke({
color: options.symbology.values[i].styleOptions.color,
width: options.symbology.values[i].styleOptions.width
}));
break;
}
}
}
}
break;
case "range":
// Its a range symbology. Check if the features property value is in the range set in the symbology and style accordingly
//
var att = options.symbology.property;
for (var i = 0, len = options.symbology.ranges.length; i < len; i++) {
if (atts[att] >= options.symbology.ranges[i].range[0] && atts[att] <= options.symbology.ranges[i].range[1]) {
for (var key in options.symbology.ranges[i].styleOptions) {
switch (feature.getGeometry().getType()) {
case "Point":
case "MultiPoint":
style.image = style.getImage().getFill().setColor(options.symbology.ranges[i].styleOptions.fill);
style.image = style.getImage().getStroke().setColor(options.symbology.ranges[i].styleOptions.color);
style.image = style.getImage().getStroke().setWidth(options.symbology.ranges[i].styleOptions.width);
style.image = style.getImage().setRadius(options.symbology.ranges[i].styleOptions.radius);
break;
case "LineString":
case "MultiLineString":
case "Polygon":
case "MultiPolygon":
style.fill = style.setFill(new ol.style.Fill({
color: options.symbology.ranges[i].styleOptions.fill
}));
style.stroke = style.setStroke(new ol.style.Stroke({
color: options.symbology.ranges[i].styleOptions.color,
width: options.symbology.ranges[i].styleOptions.width
}));
break;
}
}
}
}
break;
}
}
return styles;
}
})()
}
ol.layer.Vector.call(this, options);
};
ol.inherits(ol3Vector, ol.layer.Vector);
aquí un ejemplo de map.js
function init() {
document.removeEventListener('DOMContentLoaded', init);
//
// ------- Layers and Map ----------------
//
var baselayers = new ol.layer.Group({
title: 'Baselayers',
layers: [
new ol.layer.Tile({
title: 'OSM',
type: 'base',
visible: true,
source: new ol.source.OSM()
})
]
});
var toplayers = new ol.layer.Group({
title: 'Toplayer',
layers: []
});
var view = new ol.View({
center: ol.proj.fromLonLat([6.2, 49.6]),
zoom: 12
});
var popup_div = document.getElementById('popup');
var popup = new ol.Overlay({
element: popup_div,
positioning: 'bottom-center',
stopEvent: false
});
var map = new ol.Map({
target: 'map',
view: view,
controls: ol.control.defaults().extend([
new ol.control.Zoom(),
new ol.control.FullScreen(),
new ol.control.ZoomSlider(),
new ol.control.LayerSwitcher({ //layergroups are used with the layerswitcher from https://github.com/walkermatt/ol3-layerswitcher
tipLabel: 'Layer Switcher'
}),
new ol.control.OverviewMap(),
new ol.control.ScaleLine()
]),
overlays: [popup],
layers: [baselayers, toplayers],
interactions: ol.interaction.defaults().extend([
new ol.interaction.Select({
layers: [baselayers, toplayers]
})
])
});
//
// ------------ define toplayers -------------------
//
var n2k_dh_l = new ol3Vector({
title: "Natura 2000 Habitats Directive", // name of the layer to show up in the layerswitcher
attribution: "<br />Réseau Natura 2000 Habitats Directive",
geotable: "n2k_dh",
fields: "gid as id, sitecode, sitename, surfha",
where: "sitename ilike '%moselle%'", // You can use all the PostgreSQL or PostGis features here
symbology: {
type: "single",
styleOptions: {
fill: "rgba(100,250,0,0.1)", // define colors as rgba()
color: "green", // or simple color-names
width: 2
}
},
minResolution: 0.01,
maxResolution: 50,
content: "<p><strong> BH {sitecode}</strong><hr>{sitename}<br />{surfha} ha </p>",
showLabels: true, // show labels on map
label: "sitename" // field used for labeling
});
var n2k_do_l = new ol3Vector({
title: "Natura 2000 Birds Directive",
attribution: "<br />Réseau Natura 2000 Birds Directive",
geotable: "n2k_do",
fields: "gid as id, sitecode, sitename, surfha",
where: "",
symbology: {
type: "single",
styleOptions: {
fill: "rgba(100,250,0,0.1)",
color: "magenta",
width: 2
}
},
minResolution: 0.01,
maxResolution: 50,
content: "<p><strong> BD {sitecode}</strong><hr>{sitename}<br />{surfha} ha </p>",
showLabels: true,
label: "sitecode"
});
var communes = new ol3Vector({
map: map,
title: "Communes",
attribution: "<br />Communes",
geotable: "communes",
fields: "gid as id, surfha, commune, stats",
where: "",
symbology: {
type: "unique",
property: "stats", // field used to style depending on their value
values: [{
value: "AB",
styleOptions: {
fill: "rgba(0,0,0,0.0)",
color: "grey",
width: 1.25
}
},
{
value: "CD",
styleOptions: {
fill: "rgba(100,250,0,0.1)",
color: "green",
width: 2
}
},
{
value: "",
styleOptions: {
fill: "rgba(250,0,0,0.1)",
color: "red",
width: 2
}
}
]
},
minResolution: 0.01,
maxResolution: 50,
content: "<p><strong>{commune}</strong><hr>{stat}<br />{surfha} ha </p>",
showLabels: true,
label: "commune"
});
var n2k_dh_r = new ol3Vector({
map: map,
title: "Natura 2000 Habitats Directive - site size",
attribution: "<br />Réseau Natura 2000 Habitats Directive",
geotable: "n2k_dh",
fields: "gid as id, sitecode, sitename, surfha",
where: "",
symbology: {
type: "range",
property: "surfha", // field that holds values that should be displayed as ranges
ranges: [{
range: [1, 100], // defining range min and max values of property field
styleOptions: {
fill: "rgba(220,20,60,0.3)",
color: "crimson",
width: 1
}
}, {
range: [101, 1000],
styleOptions: {
fill: "rgba(255,165,0,0.3)",
color: "orange",
width: 1
}
}, {
range: [1001, 10000],
styleOptions: {
fill: "rgba(255,255,0,0.3)",
color: "Yellow",
width: 1
}
}]
},
minResolution: 0.01,
maxResolution: 50,
content: "<p><strong> BH {sitecode}</strong><hr>{sitename}<br />{surfha} ha </p>",
showLabels: true,
label: "sitecode"
});
var btk_p = new ol3Vector({
map: map,
title: "Habitats points", // point layers
attribution: "<br />Cartho",
geotable: "btk_p",
fields: "gid as id, btyp1_code, btyp1_name, cs",
where: "",
symbology: {
type: "unique",
property: "cs",
values: [{
value: "A",
styleOptions: {
fill: "rgba(0,128,0,0.3)",
color: "rgba(0,128,0,0.3)",
width: 1,
radius: 20 // must be set in order to render point features
}
},
{
value: "B",
styleOptions: {
fill: "rgba(255,165,0,0.3)",
color: "rgba(255,165,0,0.3)",
width: 1,
radius: 15
}
},
{
value: "C",
styleOptions: {
fill: "rgba(255,0,0,0.3)",
color: "rgba(255,0,0,0.3)",
width: 1,
radius: 10
}
}
]
},
minResolution: 0.01,
maxResolution: 50,
content: "<p><strong>{btyp1_code}</strong><hr>{btyp1_name}<br />{cs}</p>",
showLabels: false,
label: "bewertung1"
});
// ------------------ add ol3Vectors to toplayers ----------
//
toplayers.setLayers(new ol.Collection([n2k_do_l, n2k_dh_l, communes, n2k_dh_r, btk_p]));
//
// ------------------ show popups based on content-template for different layers --------------------
//
map.on('click', function(evt) {
var feature = map.forEachFeatureAtPixel(evt.pixel,
function(feature, layer) {
return feature;
});
var popupContent = map.forEachLayerAtPixel(evt.pixel,
function(layer) {
return layer.get('content');
});
if (feature) {
popup.setPosition(evt.coordinate);
var atts = feature.getProperties();
for (var prop in atts) {
var re = new RegExp("{" + prop + "}", "g");
popupContent = popupContent.replace(re, atts[prop]);
}
$(popup_div).attr('data-placement', 'auto');
$(popup_div).attr('data-content', popupContent);
$(popup_div).attr('data-html', true);
$(popup_div).popover();
$(popup_div).popover('show');
$('.popover-title').click(function() {
$(popup_div).popover('destroy');
});
} else {
$(popup_div).popover('destroy');
}
});
} // End function init()
document.addEventListener('DOMContentLoaded', init);
Finalmente, necesitamos get_geojson.php para obtener datos de la base de datos PostGis.
<?php
/**
* GET GeoJSON from PostGIS
* Query a PostGIS table or view and return the results in GeoJSON format, suitable for use in OpenLayers, Leaflet, etc.
* Author: Bryan R. McBride, GISP, adapted by G.Moes
* Contact: bryanmcbride.com
* GitHub: https://github.com/bmcbride/PHP-Database-GeoJSON
*
* @param string $geotable The PostGIS layer name *REQUIRED*
* @param string $geomfield The PostGIS geometry field *REQUIRED*
* @param string $srid The SRID of the returned GeoJSON *OPTIONAL (If omitted, EPSG: 2169 will be used)*
* @param string $fields Fields to be returned *OPTIONAL (If omitted, all fields will be returned)*
* NOTE- Uppercase field names should be wrapped in double quotes
* @param string $parameters SQL WHERE clause parameters *OPTIONAL*
* @param string $orderby SQL ORDER BY constraint *OPTIONAL*
* @param string $sort SQL ORDER BY sort order (ASC or DESC) *OPTIONAL*
* @param string $limit Limit number of results returned *OPTIONAL*
* @param integer $precision digits of returned geojson 6 = 0.111 m submeter as DEFAULT *OPTIONAL*
* @param real $simplify simplify geometry to >5.0m as DEFAULT *OPTIONAL*
* @param string $offset Offset used in conjunction with limit *OPTIONAL*
* @return string resulting geojson string
*/
# Connect to PostgreSQL database You need to pass here the credentials to connect to Your database
require("../database/connect.php");
function escapeJsonString($value) { # list from www.json.org: (\b backspace, \f formfeed)
$escapers = array("\\", "/", "\"", "\n", "\r", "\t", "\x08", "\x0c");
$replacements = array("\\\\", "\\/", "\\\"", "\\n", "\\r", "\\t", "\\f", "\\b");
$result = str_replace($escapers, $replacements, $value);
return $result;
}
# Retrive URL variables
if (empty($_GET['geotable'])) {
echo "missing required parameter: <i>geotable</i>";
exit;
} else
$geotable = $_GET['geotable'];
if (empty($_GET['geomfield'])) {
$geomfield='the_geom';
} else
$geomfield = $_GET['geomfield'];
if (empty($_GET['srid'])) {
$srid = 2169; // changethis if You need another standard SRID
} else
$srid = $_GET['srid'];
if (empty($_GET['fields'])) {
$fields = '*';
} else
$fields = $_GET['fields'];
$parameters = $_GET['where'];
$bbox = $_GET['bbox'];
if (empty($_GET['precision'])) {
$precision = 6; // change this to Your needs
} else
$precision = $_GET['precision'];
if (empty($_GET['simplify'])) {
$simplify = 5.0; // change this to Your needs
} else
$simplify = $_GET['simplify'];
$orderby = $_GET['orderby'];
if (empty($_GET['sort'])) {
$sort = 'ASC';
} else
$sort = $_GET['sort'];
$limit = $_GET['limit'];
$offset = $_GET['offset'];
# Build SQL SELECT statement and return the geometry as a GeoJSON element in EPSG: 4326
$sql = "SELECT " . pg_escape_string($fields) . ", st_asgeojson(st_transform(ST_SimplifyPreserveTopology(" . pg_escape_string($geomfield) . ",".$simplify."),4326),".$precision.") AS geojson FROM " . pg_escape_string($geotable);
if (strlen(trim($parameters)) > 0) {
$sql .= " WHERE " . str_replace("''", "'", pg_escape_string($parameters));
}
if (strlen(trim($parameters)) > 0 AND strlen(trim($bbox)) > 0){
$sql .= " AND the_geom && st_transform(st_makeenvelope(".pg_escape_string ($bbox).",4326),".$srid.")";
}
if (strlen(trim($parameters)) <= 0 AND strlen(trim($bbox)) > 0) {
$sql .= " WHERE the_geom && st_transform(st_makeenvelope(".pg_escape_string ($bbox).",4326),".$srid.")";
}
if (strlen(trim($orderby)) > 0) {
$sql .= " ORDER BY " . pg_escape_string($orderby) . " " . $sort;
}
if (strlen(trim($limit)) > 0) {
$sql .= " LIMIT " . pg_escape_string($limit);
}
if (strlen(trim($offset)) > 0) {
$sql .= " OFFSET " . pg_escape_string($offset);
}
//echo $sql;
# Try query or error
$rs = pg_query($db_handle, $sql);
if (!$rs) {
echo "An SQL error occured.\n";
echo $sql;
exit;
}
# Build GeoJSON
$output = '';
$rowOutput = '';
while ($row = pg_fetch_assoc($rs)) {
$rowOutput = (strlen($rowOutput) > 0 ? ',' : '') . '{"type": "Feature", "geometry": ' . $row['geojson'] . ', "properties": {';
$props = '';
$id = '';
foreach ($row as $key => $val) {
if ($key != "geojson") {
$props .= (strlen($props) > 0 ? ',' : '') . '"' . $key . '":"' . escapeJsonString($val) . '"';
}
if ($key == "id") {
$id .= ',"id":"' . escapeJsonString($val) . '"';
}
}
$rowOutput .= $props . '}';
$rowOutput .= $id;
$rowOutput .= '}';
$output .= $rowOutput;
}
$output = '{"type": "FeatureCollection", "features": [ ' . $output . ' ]}';
header('Content-type:application/json;charset=utf-8');
echo json_encode( $output);
?>
¡Que te diviertas! Que esto ayude a alguien a ir más allá o mejorar este código y publicarlo en GitHub.