ashatora/openlayers
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Giving the getCentroid method on geometry collections a 'weighted' argument. If true, the centroid will be calculated based on the weighted average of all component centroids. Thanks for the great patch dzwarg. r=me (closes #2469)

Browse Source 
git-svn-id: http://svn.openlayers.org/trunk/openlayers@10652 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
This commit is contained in:
Tim Schaub
2010-08-20 20:28:48 +00:00
parent 2c7eade60c
commit 28558c171c
2 changed files with 199 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

69
lib/OpenLayers/Geometry/Collection.js
View File

@@ -261,22 +261,67 @@ OpenLayers.Geometry.Collection = OpenLayers.Class(OpenLayers.Geometry, {
/**
* APIMethod: getCentroid
*
* Compute the centroid for this geometry collection.
*
* Parameters:
* weighted - {Boolean} Perform the getCentroid computation recursively,
* returning an area weighted average of all geometries in this collection.
*
* Returns:
* {<OpenLayers.Geometry.Point>} The centroid of the collection
*/
getCentroid: function() {
return this.components.length && this.components[0].getCentroid();
/*
var centroid;
for (var i=0, len=this.components.length; i<len; i++) {
if (!centroid) {
centroid = this.components[i].getCentroid();
} else {
centroid.resize(this.components[i].getCentroid(), 0.5);
}
getCentroid: function(weighted) {
if (!weighted) {
return this.components.length && this.components[0].getCentroid();
}
return centroid;
*/
var len = this.components.length;
if (!len) {
return false;
}
var areas = [];
var centroids = [];
var areaSum = 0;
var minArea = Number.MAX_VALUE;
var component;
for (var i=0; i<len; ++i) {
component = this.components[i];
var area = component.getArea();
var centroid = component.getCentroid(true);
if (isNaN(area) || isNaN(centroid.x) || isNaN(centroid.y)) {
continue;
}
areas.push(area);
areaSum += area;
minArea = (area < minArea && area > 0) ? area : minArea;
centroids.push(centroid);
}
len = areas.length;
if (areaSum === 0) {
// all the components in this collection have 0 area
// probably a collection of points -- weight all the points the same
for (var i=0; i<len; ++i) {
areas[i] = 1;
}
areaSum = areas.length;
} else {
// normalize all the areas where the smallest area will get
// a value of 1
for (var i=0; i<len; ++i) {
areas[i] /= minArea;
}
areaSum /= minArea;
}
var xSum = 0, ySum = 0, centroid, area;
for (var i=0; i<len; ++i) {
centroid = centroids[i];
area = areas[i];
xSum += centroid.x * area;
ySum += centroid.y * area;
}
return new OpenLayers.Geometry.Point(xSum/areaSum, ySum/areaSum);
},
/**

142
tests/Geometry/Collection.html
View File

@@ -250,6 +250,148 @@
t.eq(multipoint.bounds, null, "multipoint component bounds cleared");
}
function test_getCentroid_pts_only(t) {
t.plan(3);
coll = new OpenLayers.Geometry.Collection();
coll.addComponent(new OpenLayers.Geometry.Point(0,0));
coll.addComponent(new OpenLayers.Geometry.Point(1,1));
centroid = coll.getCentroid(true);
t.ok(centroid != null, 'The centroid is not null.');
t.eq(centroid.x, 0.5, 'The centroid x coordinate is good.');
t.eq(centroid.y, 0.5, 'The centroid y coordinate is good.');
coll.destroy();
}
function test_getCentroid_poly_nonrecursive(t) {
t.plan(3);
coll = new OpenLayers.Geometry.Collection();
coll.addComponent(
new OpenLayers.Geometry.Polygon([
new OpenLayers.Geometry.LinearRing([
new OpenLayers.Geometry.Point(0,0),
new OpenLayers.Geometry.Point(0,1),
new OpenLayers.Geometry.Point(1,1),
new OpenLayers.Geometry.Point(1,0)
])
])
);
// performing non-recursive getCentroid means this next polygon
// is excluded from the centroid computation
coll.addComponent(
new OpenLayers.Geometry.Polygon([
new OpenLayers.Geometry.LinearRing([
new OpenLayers.Geometry.Point(2,2),
new OpenLayers.Geometry.Point(2,3),
new OpenLayers.Geometry.Point(3,3),
new OpenLayers.Geometry.Point(3,2)
])
])
);
centroid = coll.getCentroid();
t.ok(centroid != null, 'The centroid is not null.');
t.eq(centroid.x, 0.5, 'The centroid x coordinate is good.');
t.eq(centroid.y, 0.5, 'The centroid y coordinate is good.');
coll.destroy();
}
function test_getCentroid_poly_only(t) {
t.plan(3);
coll = new OpenLayers.Geometry.Collection();
coll.addComponent(
new OpenLayers.Geometry.Polygon([
new OpenLayers.Geometry.LinearRing([
new OpenLayers.Geometry.Point(0,0),
new OpenLayers.Geometry.Point(0,1),
new OpenLayers.Geometry.Point(1,1),
new OpenLayers.Geometry.Point(1,0)
])
])
);
centroid = coll.getCentroid(true);
t.ok(centroid != null, 'The centroid is not null.');
t.eq(centroid.x, 0.5, 'The centroid x coordinate is good.');
t.eq(centroid.y, 0.5, 'The centroid y coordinate is good.');
coll.destroy();
}
function test_getCentroid_poly_and_pts(t) {
t.plan(3);
coll = new OpenLayers.Geometry.Collection();
coll.addComponent(
new OpenLayers.Geometry.Polygon([
new OpenLayers.Geometry.LinearRing([
new OpenLayers.Geometry.Point(0,0),
new OpenLayers.Geometry.Point(0,1),
new OpenLayers.Geometry.Point(1,1),
new OpenLayers.Geometry.Point(1,0)
])
])
);
// since the polygon above has an area of 1 and these
// points have an area of 0, they should not change the centroid
coll.addComponent( new OpenLayers.Geometry.Point(2,2) );
coll.addComponent( new OpenLayers.Geometry.Point(4,4) );
centroid = coll.getCentroid(true);
t.ok(centroid != null, 'The centroid is not null.');
t.eq(centroid.x, 0.5, 'The centroid x coordinate is good.');
t.eq(centroid.y, 0.5, 'The centroid y coordinate is good.');
coll.destroy();
}
function test_getCentroid_poly_big_and_small(t) {
t.plan(3);
coll = new OpenLayers.Geometry.Collection();
// polygon w/area=1, centroid=0.5,0.5
coll.addComponent(
new OpenLayers.Geometry.Polygon([
new OpenLayers.Geometry.LinearRing([
new OpenLayers.Geometry.Point(0,0),
new OpenLayers.Geometry.Point(0,1),
new OpenLayers.Geometry.Point(1,1),
new OpenLayers.Geometry.Point(1,0)
])
])
);
// since the polygon above has an area of 1 and this
// polygon has an area of 4, the center is weighted 20% toward
// the first polygon
// polygon w/area=4, centroid=5.5,5.5
coll.addComponent(
new OpenLayers.Geometry.Polygon([
new OpenLayers.Geometry.LinearRing([
new OpenLayers.Geometry.Point(4.5,-0.5),
new OpenLayers.Geometry.Point(4.5,1.5),
new OpenLayers.Geometry.Point(6.5,1.5),
new OpenLayers.Geometry.Point(6.5,-0.5)
])
])
);
centroid = coll.getCentroid(true);
t.ok(centroid != null, 'The centroid is not null.');
t.eq(centroid.x, 4.5, 'The centroid x coordinate is good.');
t.eq(centroid.y, 0.5, 'The centroid y coordinate is good.');
coll.destroy();
}
function test_Collection_destroy(t) {
t.plan( 3 );