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Refactoring
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Lucas Wojciechowski committed May 26, 2016
1 parent c2d5d04 commit 7b9ef15
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Showing 2 changed files with 74 additions and 60 deletions.
20 changes: 9 additions & 11 deletions js/util/classify_rings.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,11 +2,8 @@

var quickselect = require('quickselect');

module.exports = classifyRings;

// classifies an array of rings into polygons with outer rings and holes

function classifyRings(rings, maxRings) {
module.exports = function classifyRings(rings, maxRings) {
var len = rings.length;

if (len <= 1) return [rings];
Expand All @@ -16,7 +13,7 @@ function classifyRings(rings, maxRings) {
ccw;

for (var i = 0; i < len; i++) {
var area = signedArea(rings[i]);
var area = calculateSignedArea(rings[i]);
if (area === 0) continue;

rings[i].area = Math.abs(area);
Expand All @@ -33,23 +30,24 @@ function classifyRings(rings, maxRings) {
}
if (polygon) polygons.push(polygon);

// Earcut performance degrages with the # of rings in a polygon. For this
// reason, we limit strip out all but the `maxRings` largest rings.
if (maxRings > 1) {
len = polygons.length;
for (var j = 0; j < len; j++) {
for (var j = 0; j < polygons.length; j++) {
if (polygons[j].length <= maxRings) continue;
quickselect(polygons[j], maxRings - 1, 1, polygon.length - 1, sortByArea);
quickselect(polygons[j], maxRings - 1, 1, polygon.length - 1, compareAreas);
polygons[j] = polygon.slice(0, maxRings);
}
}

return polygons;
}
};

function sortByArea(a, b) {
function compareAreas(a, b) {
return b.area - a.area;
}

function signedArea(ring) {
function calculateSignedArea(ring) {
var sum = 0;
for (var i = 0, len = ring.length, j = len - 1, p1, p2; i < len; j = i++) {
p1 = ring[i];
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114 changes: 65 additions & 49 deletions test/js/util/classify_rings.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -77,59 +77,75 @@ test('classifyRings', function(assert) {
assert.end();
});

test('classifyRings + maxRings', function(assert) {
var geometry;
var classified;
test('classifyRings + maxRings', function(t) {

geometry = [
[
{x:0, y:0},
{x:0, y:40},
{x:40, y:40},
{x:40, y:0},
{x:0, y:0}
],
[
{x:30, y:30},
{x:32, y:30},
{x:32, y:32},
{x:30, y:30}
],
[
{x:10, y:10},
{x:20, y:10},
{x:20, y:20},
{x:10, y:10}
]
];
classified = classifyRings(geometry);
assert.equal(classified.length, 1, '1 polygon');
assert.equal(classified[0].length, 3, 'polygon 1 has 1 exterior, 2 interior');
assert.equal(classified[0][0].area, 3200, 'polygon 1 exterior ring has area=3200');
assert.equal(classified[0][1].area, 4, 'polygon 1 interior ring1 has area=4');
assert.equal(classified[0][2].area, 100, 'polygon 1 interior ring2 has area=100');
function createGeometry(options) {
var geometry = [
// Outer ring, area = 3200
[ {x:0, y:0}, {x:0, y:40}, {x:40, y:40}, {x:40, y:0}, {x:0, y:0} ],
// Inner ring, area = 100
[ {x:30, y:30}, {x:32, y:30}, {x:32, y:32}, {x:30, y:30} ],
// Inner ring, area = 4
[ {x:10, y:10}, {x:20, y:10}, {x:20, y:20}, {x:10, y:10} ]
];
if (options && options.reverse) {
geometry[0].reverse();
geometry[1].reverse();
geometry[2].reverse();
}
return geometry;
}

classified = classifyRings(geometry, 2);
assert.equal(classified.length, 1, '1 polygon');
assert.equal(classified[0].length, 2, 'polygon 1 has 1 exterior, 1 interior');
assert.equal(classified[0][0].area, 3200, 'polygon 1 exterior ring has area=3200');
assert.equal(classified[0][1].area, 100, 'polygon 1 interior ring has area=100');

geometry[0].reverse();
geometry[1].reverse();
geometry[2].reverse();
classified = classifyRings(geometry, 2);
assert.equal(classified.length, 1, '1 polygon');
assert.equal(classified[0].length, 2, 'polygon 1 has 1 exterior, 1 interior');
assert.equal(classified[0][0].area, 3200, 'polygon 1 exterior ring has area=3200');
assert.equal(classified[0][1].area, 100, 'polygon 1 interior ring has area=100');
t.test('maxRings=undefined', function(t) {
var geometry = sortRings(classifyRings(createGeometry()));
t.equal(geometry.length, 1);
t.equal(geometry[0].length, 3);
t.equal(geometry[0][0].area, 3200);
t.equal(geometry[0][1].area, 100);
t.equal(geometry[0][2].area, 4);
t.end();
});

geometry = feature.loadGeometry();
classified = classifyRings(geometry, 5);
assert.equal(classified.length, 2, '2 polygons');
assert.equal(classified[0].length, 1, 'polygon 1 has 1 exterior');
assert.equal(classified[1].length, 5, 'polygon 2 has 1 exterior, 4 interior');
t.test('maxRings=2', function(t) {
var geometry = sortRings(classifyRings(createGeometry(), 2));
t.equal(geometry.length, 1);
t.equal(geometry[0].length, 2);
t.equal(geometry[0][0].area, 3200);
t.equal(geometry[0][1].area, 100);
t.end();
});

assert.end();
t.test('maxRings=2, reversed geometry', function(t) {
var geometry = sortRings(classifyRings(createGeometry({reverse: true}), 2));
t.equal(geometry.length, 1);
t.equal(geometry[0].length, 2);
t.equal(geometry[0][0].area, 3200);
t.equal(geometry[0][1].area, 100);
t.end();
});

t.test('maxRings=5, geometry from fixture', function(t) {
var geometry = sortRings(classifyRings(feature.loadGeometry(), 5));
t.equal(geometry.length, 2);
t.equal(geometry[0].length, 1);
t.equal(geometry[1].length, 5);

var areas = geometry[1].map(function(ring) { return ring.area; });
t.deepEqual(areas, [2763951, 21600, 8298, 4758, 3411]);
t.end();
});

t.end();
});

function sortRings(geometry) {
for (var i = 0; i < geometry.length; i++) {
geometry[i] = geometry[i].sort(compareArea);
}
return geometry;
}

function compareAreas(a, b) {
return b.area - a.area;
}

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