feat(utils): Extent buffer

Register equidistant worldwide projection, EPSG:4087
hslayers · Jul 29, 2024 · 0f44b5c · 0f44b5c
1 parent 419862e
commit 0f44b5c
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Showing 3 changed files with 58 additions and 3 deletions.
diff --git a/projects/hslayers/services/add-data/url/wms.service.ts b/projects/hslayers/services/add-data/url/wms.service.ts
@@ -465,7 +465,11 @@ export class HsUrlWmsService implements HsUrlTypeServiceModel {
       removable: true,
       abstract: layer.Abstract,
       metadata,
-      extent: this.getLayerExtent(layer, options.crs),
+      extent: this.HsLayerUtilsService.bufferExtent(
+        //Full world in case of layers added via URL panel.
+        this.getLayerExtent(layer, options.crs),
+        this.hsMapService.getCurrentProj(),
+      ),
       path: options.path,
       dimensions: dimensions,
       legends: legends,

diff --git a/projects/hslayers/services/map/map.service.ts b/projects/hslayers/services/map/map.service.ts
@@ -568,6 +568,16 @@ export class HsMapService {
       'http://www.opengis.net/gml/srs/epsg.xml#3031',
       proj4.defs('EPSG:3031'),
     );
+
+    proj4.defs(
+      'EPSG:4087',
+      '+proj=cea +lon_0=0 +lat_ts=0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs',
+    );
+    proj4.defs(
+      'http://www.opengis.net/gml/srs/epsg.xml#4087',
+      proj4.defs('EPSG:4087'),
+    );
+
     register(proj4);
     if (this.hsConfig.componentsEnabled?.mapControls == false) {
       this.removeAllControls();

diff --git a/projects/hslayers/services/utils/layer-utils.service.ts b/projects/hslayers/services/utils/layer-utils.service.ts
@@ -12,13 +12,13 @@ import {
   WMTS,
   XYZ,
 } from 'ol/source';
+import {Extent, isEmpty} from 'ol/extent';
 import {Feature, View} from 'ol';
 import {default as FeatureFormat} from 'ol/format/Feature';
 import {Geometry} from 'ol/geom';
 import {Image as ImageLayer, Layer, Vector as VectorLayer} from 'ol/layer';
-import {METERS_PER_UNIT} from 'ol/proj';
+import {METERS_PER_UNIT, Projection, transform, transformExtent} from 'ol/proj';
 import {Tile as TileLayer} from 'ol/layer';
-import {isEmpty} from 'ol/extent';
 
 import {HsLayerDescriptor} from 'hslayers-ng/types';
 import {HsUtilsService} from './utils.service';
@@ -498,4 +498,45 @@ export class HsLayerUtilsService {
         )
       : [];
   }
+
+  /**
+   * Buffer extent by `BUFFER_FACTOR`
+   * NOTE: Not using OL because we want to extend witdh and height independently
+   */
+  bufferExtent(extent: Extent, currentMapProj: Projection) {
+    const BUFFER_FACTOR = 0.1;
+
+    const inMeters = currentMapProj.getUnits() === 'm';
+    const bounds = transform([180, 90], 'EPSG:4326', currentMapProj);
+
+    //Transform into projection suitable for area manipulation* if necessary
+    const transformed = inMeters
+      ? extent
+      : transformExtent(extent, currentMapProj, 'EPSG:4087');
+
+    //Calculate buffer values
+    const extentWidth = Math.abs(extent[2] - extent[0]);
+    const extentHeight = Math.abs(extent[3] - extent[1]);
+    const bufferWidth = extentWidth * BUFFER_FACTOR;
+    const bufferHeight = extentHeight * BUFFER_FACTOR;
+
+    //Buffer extent and transform back to currentMapProj
+    const extended = transformExtent(
+      [
+        transformed[0] - bufferWidth,
+        transformed[1] - bufferHeight,
+        transformed[2] + bufferWidth,
+        transformed[3] + bufferHeight,
+      ],
+      inMeters ? currentMapProj : 'EPSG:4087',
+      currentMapProj,
+    );
+    return [
+      // Apply safeguards to ensure the extent does not go out of bounds
+      Math.max(extended[0], bounds[1] * -1),
+      Math.max(extended[1], bounds[0] * -1),
+      Math.min(extended[2], bounds[1]),
+      Math.min(extended[3], bounds[0]),
+    ];
+  }
 }