integrating weighted breaks

mapbox · Jan 6, 2016 · 9cd5eab · 9cd5eab
1 parent eee59e0
commit 9cd5eab
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Showing 3 changed files with 21 additions and 6 deletions.
diff --git a/lib/raster.js b/lib/raster.js
@@ -164,9 +164,11 @@ Raster.prototype.getZooms = function(callback) {
   var pixelSize = utils.convertToMeters(this.details.pixelSize, utils.getUnitType(this.projection));
 
   var spatialResolutions = utils.getSpatialResolutions();
-
+  // Threshold weight = the amount to shift the break;
+  // 0 = no shift (always upsamples), 1 = full shift (always downsamples)
+  var thresholdWeight = 0.25;
   var _this = this;
-  var validSpatialResolutions = utils.getValidSpatialResolutions(spatialResolutions, _this.details.pixelSize[0]);
+  var validSpatialResolutions = utils.getValidSpatialResolutions(spatialResolutions, _this.details.pixelSize[0], thresholdWeight);
 
   this.details.pixelSize = pixelSize;
   return callback(

diff --git a/lib/utils.js b/lib/utils.js
@@ -94,8 +94,9 @@ module.exports.getSpatialResolutions = function() {
   });
 };
 
-module.exports.getValidSpatialResolutions = function(spatialResolutions, pixelSize) {
-  return spatialResolutions.filter(function(res) {
-    return res > pixelSize;
+module.exports.getValidSpatialResolutions = function(spatialResolutions, pixelSize, thresholdWeight) {
+  return spatialResolutions.filter(function(res, i) {
+    var zBreak = res - spatialResolutions[Math.min(i + 1, spatialResolutions.length - 1)] * thresholdWeight;
+    return zBreak > pixelSize;
   });
 };
diff --git a/test/raster.test.js b/test/raster.test.js
@@ -403,9 +403,21 @@ tape('[SPATIAL RESOLUTIONS] Get spatial resolutions / valid spatial resolutions'
   var expectedResolutions = JSON.parse('[156542.96875,78271.484375,39135.7421875,19567.87109375,9783.935546875,4891.9677734375,2445.98388671875,1222.991943359375,611.4959716796875,305.74798583984375,152.87399291992188,76.43699645996094,38.21849822998047,19.109249114990234,9.554624557495117,4.777312278747559,2.3886561393737793,1.1943280696868896,0.5971640348434448,0.2985820174217224]');
   assert.deepLooseEqual(spatialResolutions, expectedResolutions);
 
-  var validSpatialResolutions = utils.getValidSpatialResolutions(spatialResolutions, 30.20012);
+  var validSpatialResolutions = utils.getValidSpatialResolutions(spatialResolutions, 30.20012, 0);
   var expectedValidResolutions = JSON.parse('[156542.96875,78271.484375,39135.7421875,19567.87109375,9783.935546875,4891.9677734375,2445.98388671875,1222.991943359375,611.4959716796875,305.74798583984375,152.87399291992188,76.43699645996094,38.21849822998047]');
   assert.deepLooseEqual(validSpatialResolutions, expectedValidResolutions);
 
   assert.end();
 });
+
+tape('[SPATIAL RESOLUTIONS] Get spatial resolutions / valid spatial resolutions with weight', function(assert) {
+  var spatialResolutions = utils.getSpatialResolutions();
+  var expectedResolutions = JSON.parse('[156542.96875,78271.484375,39135.7421875,19567.87109375,9783.935546875,4891.9677734375,2445.98388671875,1222.991943359375,611.4959716796875,305.74798583984375,152.87399291992188,76.43699645996094,38.21849822998047,19.109249114990234,9.554624557495117,4.777312278747559,2.3886561393737793,1.1943280696868896,0.5971640348434448,0.2985820174217224]');
+  assert.deepLooseEqual(spatialResolutions, expectedResolutions);
+
+  var validSpatialResolutions = utils.getValidSpatialResolutions(spatialResolutions, 40.20012, 0.25);
+  var expectedValidResolutions = JSON.parse('[156542.96875,78271.484375,39135.7421875,19567.87109375,9783.935546875,4891.9677734375,2445.98388671875,1222.991943359375,611.4959716796875,305.74798583984375,152.87399291992188,76.43699645996094]');
+  assert.deepLooseEqual(validSpatialResolutions, expectedValidResolutions);
+
+  assert.end();
+});