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Implement polygon-smooth and its tests (dartclub#127)
* initial implementation, and refactor * finished test and benchmark impl * reference in README
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,21 @@ | ||
| import 'dart:convert'; | ||
| import 'dart:io'; | ||
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|
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| import 'package:benchmark/benchmark.dart'; | ||
| import 'package:turf/polygon_smooth.dart'; | ||
| import 'package:turf/turf.dart'; | ||
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|
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| main() { | ||
| group("turf-polygon-smooth", () { | ||
| var inDir = Directory('./test/examples/polygonSmooth/in'); | ||
| for (var file in inDir.listSync(recursive: true)) { | ||
| if (file is File && file.path.endsWith('.geojson')) { | ||
| benchmark(file.path, () { | ||
| var inSource = file.readAsStringSync(); | ||
| var inGeom = GeoJSONObject.fromJson(jsonDecode(inSource)); | ||
| polygonSmooth(inGeom, iterations: 3); | ||
| }); | ||
| } | ||
| } | ||
| }); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,3 @@ | ||
| library turf_polygon_smooth; | ||
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| export 'src/polygon_smooth.dart'; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,152 @@ | ||
| import 'package:turf/meta.dart'; | ||
| import 'package:turf/turf.dart'; | ||
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| /// | ||
| /// Smooths a [Polygon], [MultiPolygon], also inside [Feature]s, [FeatureCollection]s, or [GeometryCollection]. Based on [Chaikin's algorithm](http://graphics.cs.ucdavis.edu/education/CAGDNotes/Chaikins-Algorithm/Chaikins-Algorithm.html). | ||
| /// Warning: may create degenerate polygons. | ||
| /// The optional parameter [iterations] is the number of times to smooth the polygon. A higher value means a smoother polygon. | ||
| /// The functions returns a [FeatureCollection] of [Polygon]s and [MultiPolygon]s. | ||
| /// | ||
| /// ```dart | ||
| /// var polygon = Polygon(coordinates: [ | ||
| /// [ | ||
| /// Position(11, 0), | ||
| /// Position(22, 4), | ||
| /// Position(31, 0), | ||
| /// Position(31, 11), | ||
| /// Position(21, 15), | ||
| /// Position(11, 11), | ||
| /// Position(11, 0), | ||
| /// ] | ||
| /// ]); | ||
| /// | ||
| /// var smoothed = polygonSmooth(polygon, iterations: 3); | ||
| /// ``` | ||
| FeatureCollection polygonSmooth(GeoJSONObject inputPolys, | ||
| {int iterations = 1}) { | ||
| var outPolys = <Feature>[]; | ||
|
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| geomEach(inputPolys, ( | ||
| GeometryType? geom, | ||
| int? geomIndex, | ||
| Map<String, dynamic>? featureProperties, | ||
| BBox? featureBBox, | ||
| dynamic featureId, | ||
| ) { | ||
| var outCoords; | ||
| var poly; | ||
| var tempOutput; | ||
|
|
||
| switch (geom?.type) { | ||
| case GeoJSONObjectType.polygon: | ||
| outCoords = <List<Position>>[[]]; | ||
| for (var i = 0; i < iterations; i++) { | ||
| tempOutput = <List<Position>>[[]]; | ||
| poly = geom; | ||
| if (i > 0) poly = Polygon(coordinates: outCoords); | ||
| _processPolygon(poly, tempOutput); | ||
| outCoords = List<List<Position>>.of(tempOutput); | ||
| } | ||
| outPolys.add(Feature( | ||
| geometry: Polygon(coordinates: outCoords), | ||
| properties: featureProperties)); | ||
| break; | ||
| case GeoJSONObjectType.multiPolygon: | ||
| outCoords = [ | ||
| [<Position>[]] | ||
| ]; | ||
| for (var y = 0; y < iterations; y++) { | ||
| tempOutput = <List<List<Position>>>[ | ||
| [[]] | ||
| ]; | ||
| poly = geom; | ||
| if (y > 0) poly = MultiPolygon(coordinates: outCoords); | ||
| _processMultiPolygon(poly, tempOutput); | ||
| outCoords = List<List<List<Position>>>.of(tempOutput); | ||
| } | ||
| outPolys.add(Feature( | ||
| geometry: MultiPolygon(coordinates: outCoords), | ||
| properties: featureProperties)); | ||
| break; | ||
| default: | ||
| throw Exception("geometry is invalid, must be Polygon or MultiPolygon"); | ||
| } | ||
| }); | ||
| return FeatureCollection(features: outPolys); | ||
| } | ||
|
|
||
| _processPolygon(Polygon poly, List<List<Position>> tempOutput) { | ||
| var prevGeomIndex = 0; | ||
| var subtractCoordIndex = 0; | ||
|
|
||
| coordEach(poly, (currentCoord, coordIndex, featureIndex, multiFeatureIndex, | ||
| geometryIndex) { | ||
| if (geometryIndex! > prevGeomIndex) { | ||
| prevGeomIndex = geometryIndex; | ||
| subtractCoordIndex = coordIndex!; | ||
| tempOutput.add([]); | ||
| } | ||
| var realCoordIndex = coordIndex! - subtractCoordIndex; | ||
| var p1 = poly.coordinates[geometryIndex][realCoordIndex + 1]; | ||
| var p0x = currentCoord!.lng; | ||
| var p0y = currentCoord.lat; | ||
| var p1x = p1.lng; | ||
| var p1y = p1.lat; | ||
| tempOutput[geometryIndex].add(Position( | ||
| 0.75 * p0x + 0.25 * p1x, | ||
| 0.75 * p0y + 0.25 * p1y, | ||
| )); | ||
| tempOutput[geometryIndex].add(Position( | ||
| 0.25 * p0x + 0.75 * p1x, | ||
| 0.25 * p0y + 0.75 * p1y, | ||
| )); | ||
| }, true); | ||
| for (var ring in tempOutput) { | ||
| ring.add(ring[0]); | ||
| } | ||
| } | ||
|
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||
| _processMultiPolygon(poly, List<List<List<Position>>> tempOutput) { | ||
| var prevGeomIndex = 0; | ||
| var subtractCoordIndex = 0; | ||
| var prevMultiIndex = 0; | ||
|
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||
| coordEach(poly, (currentCoord, coordIndex, featureIndex, multiFeatureIndex, | ||
| geometryIndex) { | ||
| if (multiFeatureIndex! > prevMultiIndex) { | ||
| prevMultiIndex = multiFeatureIndex; | ||
| subtractCoordIndex = coordIndex!; | ||
| tempOutput.add([[]]); | ||
| } | ||
| if (geometryIndex! > prevGeomIndex) { | ||
| prevGeomIndex = geometryIndex; | ||
| subtractCoordIndex = coordIndex!; | ||
| tempOutput[multiFeatureIndex].add([]); | ||
| } | ||
| var realCoordIndex = coordIndex! - subtractCoordIndex; | ||
| if (realCoordIndex + 1 == | ||
| poly.coordinates[multiFeatureIndex][geometryIndex].length) { | ||
| return; | ||
| } | ||
| var p1 = | ||
| poly.coordinates[multiFeatureIndex][geometryIndex][realCoordIndex + 1]; | ||
| var p0x = currentCoord!.lng; | ||
| var p0y = currentCoord.lat; | ||
| var p1x = p1.lng; | ||
| var p1y = p1.lat; | ||
| tempOutput[multiFeatureIndex][geometryIndex].add(Position( | ||
| 0.75 * p0x + 0.25 * p1x, | ||
| 0.75 * p0y + 0.25 * p1y, | ||
| )); | ||
| tempOutput[multiFeatureIndex][geometryIndex].add(Position( | ||
| 0.25 * p0x + 0.75 * p1x, | ||
| 0.25 * p0y + 0.75 * p1y, | ||
| )); | ||
| }, true); | ||
|
|
||
| for (var poly in tempOutput) { | ||
| for (var ring in poly) { | ||
| ring.add(ring[0]); | ||
| } | ||
| } | ||
| } |
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