Add ol.Extent.getForView2DAndSize

src/ol/extent.js

@@ -45,6 +45,32 @@ ol.Extent.boundingExtent = function(var_args) {
 };
 
 
+/**
+ * @param {ol.Coordinate} center Center.
+ * @param {number} resolution Resolution.
+ * @param {number} rotation Rotation.
+ * @param {ol.Size} size Size.
+ * @return {ol.Extent} Extent.
+ */
+ol.Extent.getForView2DAndSize = function(center, resolution, rotation, size) {
+  var x = resolution * size.width / 2;
+  var y = resolution * size.height / 2;
+  var corners = [
+    new ol.Coordinate(-x, -y),
+    new ol.Coordinate(-x, y),
+    new ol.Coordinate(x, -y),
+    new ol.Coordinate(x, y)
+  ];
+  var corner;
+  for (i = 0; i < 4; ++i) {
+    corner = corners[i];
+    corner.rotate(rotation);
+    corner.add(center);
+  }
+  return ol.Extent.boundingExtent.apply(null, corners);
+};
+
+
 /**
  * Checks if the passed coordinate is contained or on the edge
  * of the extent.

test/spec/ol/extent.test.js

@@ -97,8 +97,59 @@ describe('ol.Extent', function() {
     });
 
   });
+
+  describe('getForView2DAndSize', function() {
+
+    it('works for a unit square', function() {
+      var extent = ol.Extent.getForView2DAndSize(
+          new ol.Coordinate(0, 0), 1, 0, new ol.Size(1, 1));
+      expect(extent.minX).toBe(-0.5);
+      expect(extent.minY).toBe(-0.5);
+      expect(extent.maxX).toBe(0.5);
+      expect(extent.maxY).toBe(0.5);
+    });
+
+    it('works for center', function() {
+      var extent = ol.Extent.getForView2DAndSize(
+          new ol.Coordinate(5, 10), 1, 0, new ol.Size(1, 1));
+      expect(extent.minX).toBe(4.5);
+      expect(extent.minY).toBe(9.5);
+      expect(extent.maxX).toBe(5.5);
+      expect(extent.maxY).toBe(10.5);
+    });
+
+    it('works for rotation', function() {
+      var extent = ol.Extent.getForView2DAndSize(
+          new ol.Coordinate(0, 0), 1, Math.PI / 4, new ol.Size(1, 1));
+      expect(extent.minX).toRoughlyEqual(-Math.sqrt(0.5), 1e-9);
+      expect(extent.minY).toRoughlyEqual(-Math.sqrt(0.5), 1e-9);
+      expect(extent.maxX).toRoughlyEqual(Math.sqrt(0.5), 1e-9);
+      expect(extent.maxY).toRoughlyEqual(Math.sqrt(0.5), 1e-9);
+    });
+
+    it('works for resolution', function() {
+      var extent = ol.Extent.getForView2DAndSize(
+          new ol.Coordinate(0, 0), 2, 0, new ol.Size(1, 1));
+      expect(extent.minX).toBe(-1);
+      expect(extent.minY).toBe(-1);
+      expect(extent.maxX).toBe(1);
+      expect(extent.maxY).toBe(1);
+    });
+
+    it('works for size', function() {
+      var extent = ol.Extent.getForView2DAndSize(
+          new ol.Coordinate(0, 0), 1, 0, new ol.Size(10, 5));
+      expect(extent.minX).toBe(-5);
+      expect(extent.minY).toBe(-2.5);
+      expect(extent.maxX).toBe(5);
+      expect(extent.maxY).toBe(2.5);
+    });
+
+  });
+
 });
 
 goog.require('ol.Coordinate');
 goog.require('ol.Extent');
+goog.require('ol.Size');
 goog.require('ol.projection');