Move Grid creation for mercator and geodetic pyramids to static methods on the Grid class

Author: jericks

src/main/groovy/geoscript/layer/Grid.groovy

@@ -57,4 +57,33 @@ class Grid {
         this.yResolution = yResolution
         this.size = this.width * this.height
     }
+
+    /**
+     * Create Grids for a Global Geodetic Pyramid as defined by
+     * http://wiki.osgeo.org/wiki/Tile_Map_Service_Specification#global-geodetic
+     * @param maxZoomLevel The max zoom level
+     * @return A List of Grids
+     */
+    static createGlobalGeodeticGrids(int maxZoomLevel) {
+        (0..maxZoomLevel).collect { int z ->
+            int col = Math.pow(2, z + 1)
+            int row = Math.pow(2, z)
+            double res = 0.703125 / Math.pow(2, z)
+            new Grid(z, col, row, res, res)
+        }
+    }
+
+    /**
+     * Create Grids for a Global Mercator Pyramid as defined by
+     * http://wiki.openstreetmap.org/wiki/Zoom_levels
+     * @param maxZoomLevel The max zoom level
+     * @return A List of Grids
+     */
+    static createGlobalMercatorGrids(int maxZoomLevel) {
+        (0..maxZoomLevel).collect { int z ->
+            int n = Math.pow(2, z)
+            double res = 156412.0 / n
+            new Grid(z, n, n, res, res)
+        }
+    }
 }

src/main/groovy/geoscript/layer/Pyramid.groovy

@@ -234,6 +234,7 @@ class Pyramid {
 
     /**
      * Create a Pyramid with Grids for common global web mercator tile sets.
+     * http://wiki.openstreetmap.org/wiki/Zoom_levels
      * @param options The optional named parameters:
      * <ul>
      *     <li>origin = The Pyramid Origin (defaults to bottom left)</li>
@@ -254,12 +255,7 @@ class Pyramid {
             tileHeight: 256
         )
         int maxZoom = options.get("maxZoom", 19)
-        p.grids = (0..maxZoom).collect { int z ->
-            int n = Math.pow(2, z)
-            // http://wiki.openstreetmap.org/wiki/Zoom_levels
-            double res = 156412.0 / n
-            new Grid(z, n, n, res, res)
-        }
+        p.grids = Grid.createGlobalMercatorGrids(maxZoom)
         p
     }
 
@@ -283,12 +279,7 @@ class Pyramid {
                 tileHeight: 256
         )
         int maxZoom = options.get("maxZoom", 19)
-        p.grids = (0..maxZoom).collect { int z ->
-            int col = Math.pow(2, z + 1)
-            int row = Math.pow(2, z)
-            double res = 0.703125 / Math.pow(2, z)
-            new Grid(z, col, row, res, res)
-        }
+        p.grids = Grid.createGlobalGeodeticGrids(maxZoom)
         p
     }
 }

src/test/groovy/geoscript/layer/GridTest.groovy

@@ -22,4 +22,28 @@ class GridTest {
         assertEquals "Grid(z:1, width:2, height:3, size:6, xResolution:520.0, yResolution:250.0)", grid.toString()
     }
 
+    @Test
+    void createGlobalGeodeticGrids() {
+        List<Grid> grids = Grid.createGlobalGeodeticGrids(5)
+        assertEquals(6, grids.size())
+        assertEquals(0, grids.get(0).z)
+        assertEquals(0.703125, grids.get(0).xResolution, 0.001)
+        assertEquals(0.703125, grids.get(0).yResolution, 0.001)
+        assertEquals(5, grids.get(5).z)
+        assertEquals(0.02197265625, grids.get(5).xResolution, 0.001)
+        assertEquals(0.02197265625, grids.get(5).yResolution, 0.001)
+    }
+
+    @Test
+    void createGlobalMercatorGrids() {
+        List<Grid> grids = Grid.createGlobalMercatorGrids(5)
+        assertEquals(6, grids.size())
+        assertEquals(0, grids.get(0).z)
+        assertEquals(156412.0, grids.get(0).xResolution, 0.001)
+        assertEquals(156412.0, grids.get(0).yResolution, 0.001)
+        assertEquals(5, grids.get(5).z)
+        assertEquals(4887.875, grids.get(5).xResolution, 0.001)
+        assertEquals(4887.875, grids.get(5).yResolution, 0.001)
+    }
+
 }