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Feature/cell-id-to-ll #2

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cdc6a16
Adding functions to convert S2CellID into S2LatLng.
Afourcat Jun 15, 2020
123ce5c
Adding basic test to check validity of the S2CellID to S2LatLng conve…
Afourcat Jun 15, 2020
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65 changes: 65 additions & 0 deletions lib/src/s2cell_id.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@ import 's2coords.dart';
import 's2coords_impl.dart';
import 's2point.dart';
export 's2point.dart';
import 's1angle.dart';
import 's2latlng.dart';
import 'util/bits/bits.dart';

Expand Down Expand Up @@ -79,6 +80,70 @@ int _lsbForLevel(int level) {

class S2CellId {
S2CellId(this._id);

S2LatLng latLng() {
S2Point p = this.rawPoint();
return S2LatLng(_latitude(p), _longitude(p));
}

List<int> faceSiTi() {
_maybeInit();
List<int> res = faceIJOrientation();
int delta = 0;
if (this.isLeaf()) {
delta = 1;
} else if (((res[1] ^ (id >> 2)) & 1) != 0) {
delta = 2;
}
return [res[0], 2 * res[1] + delta, 2 * res[2] + delta];
}


List<int> faceIJOrientation() {
int face = this.face();
int orientation = face & kSwapMask;
int nbits = _kMaxLevel - 7 * _kLookupBits;

int i = 0;
int j = 0;
for (var k = 7; k >= 0; k--) {
orientation += ((id >> (k * 2 * _kLookupBits + 1)) & ((1 << (2 * nbits)) - 1)) << 2;
orientation = _lookupIJ[orientation];
i += (orientation >> (_kLookupBits + 2)) << (k * _kLookupBits);
j += ((orientation >> 2) & ((1 << _kLookupBits) - 1)) << (k * _kLookupBits);
orientation &= (kSwapMask | kInvertMask);
nbits = _kLookupBits;
}

if (((id & -id) & 0x1111111111111110) != 0) {
orientation ^= kSwapMask;
}

return [face, i, j, orientation];
}

int face() {
return this.id >> _kPosBits;
}

bool isLeaf() {
return (id & 1) != 0;
}

S2Point rawPoint() {
List<int> res = this.faceSiTi();
return faceUVToXYZ(
res[0],
R2Point(
stToUV((0.5 / _kMaxSize) * res[1]),
stToUV((0.5 / _kMaxSize) * res[2]),
),
);
}

S1Angle _latitude(S2Point p) => S1Angle.fromRadians(atan2(p.z, sqrt(p.x * p.x + p.y * p.y)));

S1Angle _longitude(S2Point p) => S1Angle.fromRadians(atan2(p.y, p.x));

S2CellId.fromPoint(S2Point p) {
// ok
Expand Down
53 changes: 41 additions & 12 deletions test/s2geometry_test.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,17 @@ import 'package:test/test.dart';

void main() {
group('S2CellId', () {
test('S2CellID.latlng', () {
var ll = S2CellId(5185027895138811904).latLng();
var expectedLL =
S2LatLng.fromDegrees(45.78147499434792, 4.799570770239867);
expect(ll.lat.degrees.round(), expectedLL.lat.degrees.round());

var ll2 = S2CellId(226402483348101380).latLng();
var expectedLL2 =
S2LatLng.fromDegrees(-32.32163872204854, -3.232390648508235);
expect(ll2.lat.degrees.round(), expectedLL2.lat.degrees.round());
});
test('S2CellId.fromLatLng', () {
expect(
new S2CellId.fromLatLng(
Expand Down Expand Up @@ -76,24 +87,42 @@ void main() {
0xb112966aaaaaaaab);
});
test('S2CellId.parent', () {
expect(new S2CellId(0x47a1cbd595522b39).parent(), new S2CellId(0x47a1cbd595522b39).immediateParent());
expect(new S2CellId(0x47a1cbd595522b39).parent(29), new S2CellId(0x47a1cbd595522b39).immediateParent());
expect(new S2CellId(0x47a1cbd595522b39).parent(28), new S2CellId(0x47a1cbd595522b39).immediateParent().immediateParent());
expect(new S2CellId(0x47a1cbd595522b39).parent(28).id, 0x47a1cbd595522b30);
expect(new S2CellId(0x47a1cbd595522b39).parent(),
new S2CellId(0x47a1cbd595522b39).immediateParent());
expect(new S2CellId(0x47a1cbd595522b39).parent(29),
new S2CellId(0x47a1cbd595522b39).immediateParent());
expect(new S2CellId(0x47a1cbd595522b39).parent(28),
new S2CellId(0x47a1cbd595522b39).immediateParent().immediateParent());
expect(
new S2CellId(0x47a1cbd595522b39).parent(28).id, 0x47a1cbd595522b30);
expect(new S2CellId(0x47a1cbd595522b39).parent(13).level, 13);
});
test('S2CellId.operator', () {
expect(new S2CellId(0xf7a1cbd595522b39) > new S2CellId(0x07a1cbd595522b39), isTrue);
expect(new S2CellId(0xf7a1cbd595522b39) > new S2CellId(0xe7a1cbd595522b39), isTrue);
expect(new S2CellId(0x17a1cbd595522b39) > new S2CellId(0x07a1cbd595522b39), isTrue);
expect(new S2CellId(0xf7a1cbd595522b39) < new S2CellId(0x07a1cbd595522b39), isFalse);
expect(new S2CellId(0xf7a1cbd595522b39) < new S2CellId(0xe7a1cbd595522b39), isFalse);
expect(new S2CellId(0x17a1cbd595522b39) < new S2CellId(0x07a1cbd595522b39), isFalse);
expect(
new S2CellId(0xf7a1cbd595522b39) > new S2CellId(0x07a1cbd595522b39),
isTrue);
expect(
new S2CellId(0xf7a1cbd595522b39) > new S2CellId(0xe7a1cbd595522b39),
isTrue);
expect(
new S2CellId(0x17a1cbd595522b39) > new S2CellId(0x07a1cbd595522b39),
isTrue);
expect(
new S2CellId(0xf7a1cbd595522b39) < new S2CellId(0x07a1cbd595522b39),
isFalse);
expect(
new S2CellId(0xf7a1cbd595522b39) < new S2CellId(0xe7a1cbd595522b39),
isFalse);
expect(
new S2CellId(0x17a1cbd595522b39) < new S2CellId(0x07a1cbd595522b39),
isFalse);
});
test('S2CellId.toToken', () {
expect(new S2CellId(0x47a1cbd595522b39).toToken(), "47a1cbd595522b39");
expect(new S2CellId(0x47a1cbd595522b39).parent(29).toToken(), "47a1cbd595522b3c");
expect(new S2CellId(0x47a1cbd595522b39).parent(28).toToken(), "47a1cbd595522b3");
expect(new S2CellId(0x47a1cbd595522b39).parent(29).toToken(),
"47a1cbd595522b3c");
expect(new S2CellId(0x47a1cbd595522b39).parent(28).toToken(),
"47a1cbd595522b3");
});
});
}