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Avoid simplifying geometries when it will have no effect

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This commit is contained in:
Tom Payne
2013-12-06 19:35:10 +01:00
parent c6181ea9d1
commit b374d5c5b8
2 changed files with 38 additions and 4 deletions
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29
src/ol/geom/geometry.js
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@@ -87,6 +87,12 @@ ol.geom.Geometry = function() {
*/
this.simplifiedGeometryCache_ = {};
/**
* @private
* @type {number}
*/
this.simplifiedGeometryMaxMinSquaredTolerance_ = 0;
/**
* @private
* @type {number}
@@ -207,9 +213,14 @@ ol.geom.Geometry.prototype.getRevision = function() {
ol.geom.Geometry.prototype.getSimplifiedGeometry = function(squaredTolerance) {
if (this.simplifiedGeometryRevision_ != this.revision) {
goog.object.clear(this.simplifiedGeometryCache_);
this.simplifiedGeometryMaxMinSquaredTolerance_ = 0;
this.simplifiedGeometryRevision_ = this.revision;
}
if (squaredTolerance < 0) {
// If squaredTolerance is negative or if we know that simplification will not
// have any effect then just return this.
if (squaredTolerance < 0 ||
(this.simplifiedGeometryMaxMinSquaredTolerance_ !== 0 &&
squaredTolerance <= this.simplifiedGeometryMaxMinSquaredTolerance_)) {
return this;
}
var key = squaredTolerance.toString();
@@ -218,8 +229,20 @@ ol.geom.Geometry.prototype.getSimplifiedGeometry = function(squaredTolerance) {
} else {
var simplifiedGeometry =
this.getSimplifiedGeometryInternal(squaredTolerance);
this.simplifiedGeometryCache_[key] = simplifiedGeometry;
return simplifiedGeometry;
var simplifiedFlatCoordinates = simplifiedGeometry.getFlatCoordinates();
if (simplifiedFlatCoordinates.length < this.flatCoordinates.length) {
this.simplifiedGeometryCache_[key] = simplifiedGeometry;
return simplifiedGeometry;
} else {
// Simplification did not actually remove any coordinates. We now know
// that any calls to getSimplifiedGeometry with a squaredTolerance less
// than or equal to the current squaredTolerance will also not have any
// effect. This allows us to short circuit simplification (saving CPU
// cycles) and prevents the cache of simplified geometries from filling
// up with useless identical copies of this geometry (saving memory).
this.simplifiedGeometryMaxMinSquaredTolerance_ = squaredTolerance;
return this;
}
}
};

13
test/spec/ol/geom/linestring.test.js
View File

@@ -161,7 +161,7 @@ describe('ol.geom.LineString', function() {
var lineString;
beforeEach(function() {
lineString = new ol.geom.LineString(
[[0, 0], [1, 1], [3, 3], [5, 1], [6, 3], [7, 5]]);
[[0, 0], [1.5, 1], [3, 3], [5, 1], [6, 3.5], [7, 5]]);
});
describe('#getSimplifiedGeometry', function() {
@@ -186,7 +186,18 @@ describe('ol.geom.LineString', function() {
expect(simplifiedGeometry1).not.to.be(simplifiedGeometry2);
});
it('remembers the minimum squared tolerance', function() {
sinon.spy(lineString, 'getSimplifiedGeometryInternal');
var simplifiedGeometry1 = lineString.getSimplifiedGeometry(0.05);
expect(lineString.getSimplifiedGeometryInternal.callCount).to.be(1);
expect(simplifiedGeometry1).to.be(lineString);
var simplifiedGeometry2 = lineString.getSimplifiedGeometry(0.01);
expect(lineString.getSimplifiedGeometryInternal.callCount).to.be(1);
expect(simplifiedGeometry2).to.be(lineString);
});
});
});
});