fix ellipse's shell, fix maptalks/issues#552 (#2178)

* fix ellipse's shell, fix maptalks/issues#552

* fix ellipse specs

Author: fuzhenn

src/geometry/Ellipse.js

@@ -12,7 +12,7 @@ import Circle from './Circle';
  * @instance
  */
 const options = {
-    'numberOfShellPoints': 80
+    'numberOfShellPoints': 81
 };
 
 /**
@@ -102,7 +102,7 @@ class Ellipse extends CenterMixin(Polygon) {
     _getShell() {
         const measurer = this._getMeasurer(),
             center = this.getCoordinates(),
-            numberOfPoints = this.options['numberOfShellPoints'],
+            numberOfPoints = this.options['numberOfShellPoints'] - 1,
             width = this.getWidth(),
             height = this.getHeight();
         const shell = [];
@@ -125,6 +125,7 @@ class Ellipse extends CenterMixin(Polygon) {
             vertex.z = center.z;
             shell.push(vertex);
         }
+        shell.push(shell[0].copy());
         return shell;
     }
 

test/geometry/EllipseSpec.js

@@ -77,9 +77,9 @@ describe('Geometry.Ellipse', function () {
         var ellipse = new maptalks.Ellipse([0, 0], 1000, 800);
         var shell = ellipse.getShell();
 
-        var num = ellipse.options.numberOfShellPoints;
-        expect(shell).to.have.length(num);
-        var sumx = 0, sumy = 0, len = shell.length;
+        var num = ellipse.options.numberOfShellPoints - 1;
+        expect(shell).to.have.length(ellipse.options.numberOfShellPoints);
+        var sumx = 0, sumy = 0, len = shell.length - 1;
         for (var i = 0; i < len; i++) {
             sumx += shell[i].x;
             sumy += shell[i].y;
@@ -96,9 +96,9 @@ describe('Geometry.Ellipse', function () {
         var ellipse = new maptalks.Ellipse([0, 0, 100], 1000, 800);
         var shell = ellipse.getShell();
 
-        var num = ellipse.options.numberOfShellPoints;
-        expect(shell).to.have.length(num);
-        var sumx = 0, sumy = 0, len = shell.length;
+        var num = ellipse.options.numberOfShellPoints - 1;
+        expect(shell).to.have.length(ellipse.options.numberOfShellPoints);
+        var sumx = 0, sumy = 0, len = shell.length - 1;
         for (var i = 0; i < len; i++) {
             sumx += shell[i].x;
             sumy += shell[i].y;