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Merge pull request #134 from hu0p/optimize/zxy-to-tile-id

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js: Optimize zxyToTileId performance
This commit is contained in:
Brandon Liu
2023-03-13 14:22:53 +08:00
committed by GitHub
parent 744b1b82e6 bf35ff4829
commit 118049200f
1 changed files with 8 additions and 6 deletions
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14
js/index.ts
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@@ -88,6 +88,13 @@ function idOnLevel(z: number, pos: number): [number, number, number] {
return [z, xy[0], xy[1]]; return [z, xy[0], xy[1]];
} }
const tzValues: number[] = [
0, 1, 5, 21, 85, 341, 1365, 5461, 21845, 87381, 349525, 1398101, 5592405,
22369621, 89478485, 357913941, 1431655765, 5726623061, 22906492245,
91625968981, 366503875925, 1466015503701, 5864062014805, 23456248059221,
93824992236885, 375299968947541, 1501199875790165,
];
export function zxyToTileId(z: number, x: number, y: number): number { export function zxyToTileId(z: number, x: number, y: number): number {
if (z > 26) { if (z > 26) {
throw Error("Tile zoom level exceeds max safe number limit (26)"); throw Error("Tile zoom level exceeds max safe number limit (26)");
@@ -96,12 +103,7 @@ export function zxyToTileId(z: number, x: number, y: number): number {
throw Error("tile x/y outside zoom level bounds"); throw Error("tile x/y outside zoom level bounds");
} }
let acc = 0; const acc = tzValues[z];
let tz = 0;
while (tz < z) {
acc += Math.pow(2, tz) * Math.pow(2, tz);
tz++;
}
const n = Math.pow(2, z); const n = Math.pow(2, z);
let rx = 0; let rx = 0;
let ry = 0; let ry = 0;