[Feature/multi-geometry-scaling] Add scaling support for MultiPolygon, MultiLineString, and MultiPoint geometries

packages/turf-multi-geometry-scale/LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2019 Morgan Herlocker
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

packages/turf-multi-geometry-scale/README.md

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+# @turf/multiGeometryScale
+
+<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
+
+<!-- This file is automatically generated. Please don't edit it directly. If you find an error, edit the source file of the module in question (likely index.js or index.ts), and re-run "yarn docs" from the root of the turf project. -->
+
+---
+
+This module is part of the [Turfjs project](https://turfjs.org/), an open source module collection dedicated to geographic algorithms. It is maintained in the [Turfjs/turf](https://github.com/Turfjs/turf) repository, where you can create PRs and issues.
+
+### Installation
+
+Install this single module individually:
+
+```sh
+$ npm install @turf/multiGeometryScale
+```
+
+Or install the all-encompassing @turf/turf module that includes all modules as functions:
+
+```sh
+$ npm install @turf/turf
+```

packages/turf-multi-geometry-scale/index.ts

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+import { AllGeoJSON } from "@turf/helpers";
+import { centerOfMass } from "@turf/center-of-mass";
+
+function multiGeometryScale<T extends AllGeoJSON>(
+  geojson: any,
+  scaleX: number,
+  scaleY: number,
+  angle: number
+): T {
+  //Input validation
+  if (!geojson) throw new Error("geojson is invalid");
+
+  if (
+    geojson.geometry.type !== "MultiPolygon" &&
+    geojson.geometry.type !== "MultiLineString" &&
+    geojson.geometry.type !== "MultiPoint"
+  )
+    throw new Error(
+      "Only Grouped Geometry allowed. etc. MultiPolygon/MultiLineString/MultiPoint"
+    );
+
+  if (scaleX === undefined || scaleX === null || isNaN(scaleX))
+    throw new Error("scaleX is required");
+  if (scaleY === undefined || scaleY === null || isNaN(scaleY))
+    throw new Error("scaleY is required");
+  if (angle === undefined || angle === null || isNaN(angle))
+    throw new Error("angle is required");
+
+  // Shortcut no-translate
+  if (scaleX === 1 && scaleY === 1) return geojson;
+
+  let pivot = centerOfMass(geojson).geometry.coordinates;
+
+  const angleRadian = (angle * Math.PI) / 180;
+  const cos = Math.cos(angleRadian);
+  const sin = Math.sin(angleRadian);
+
+  function transformCoord([x, y]: [number, number]) {
+    // 1️⃣ translate to pivot
+    const dx = x - pivot[0];
+    const dy = y - pivot[1];
+
+    // 2️⃣ rotate -θ
+    const rx = dx * cos + dy * sin;
+    const ry = -dx * sin + dy * cos;
+
+    // 3️⃣ scale
+    const sx = rx * scaleX;
+    const sy = ry * scaleY;
+
+    // 4️⃣ rotate +θ
+    const fx = sx * cos - sy * sin;
+    const fy = sx * sin + sy * cos;
+
+    // 5️⃣ translate back
+    return [fx + pivot[0], fy + pivot[1]];
+  }
+
+  function walk(coords: any): any {
+    return coords.map((c: any) =>
+      typeof c[0] === "number" ? transformCoord(c) : walk(c)
+    );
+  }
+
+  return {
+    ...geojson,
+    geometry: {
+      ...geojson.geometry,
+      coordinates: walk(geojson.geometry.coordinates),
+    },
+  };
+}
+
+export { multiGeometryScale };
+export default multiGeometryScale;

packages/turf-multi-geometry-scale/package.json

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+{
+  "name": "@turf/multiGeometryScale",
+  "version": "1.0.0",
+  "description": "Scales a multiGeometry without disturbing the relative distance",
+  "author": "Mishor Patra",
+  "contributors": [],
+  "license": "",
+  "bugs": {
+    "url": "https://github.com/Turfjs/turf/issues"
+  },
+  "homepage": "https://github.com/Turfjs/turf",
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/Turfjs/turf.git"
+  },
+  "funding": "https://opencollective.com/turf",
+  "publishConfig": {
+    "access": "public"
+  },
+  "keywords": [
+    "turf",
+    "translate",
+    "multiPolygon",
+    "multiPoint",
+    "multiLineString"
+  ],
+  "type": "module",
+  "exports": {
+    "./package.json": "./package.json",
+    ".": {
+      "types": "./dist/index.d.ts",
+      "default": "./dist/index.js"
+    }
+  },
+  "sideEffects": false,
+  "files": [
+    "dist",
+    "!**/*.tsbuildinfo"
+  ],
+  "scripts": {
+    "bench": "tsx bench.ts",
+    "build": "tsc --build",
+    "test": "pnpm run /test:.*/",
+    "test:tape": "tsx test.ts"
+  },
+  "devDependencies": {
+    "@types/benchmark": "catalog:",
+    "@types/tape": "catalog:",
+    "benchmark": "catalog:",
+    "load-json-file": "^7.0.1",
+    "tape": "catalog:",
+    "tsx": "catalog:",
+    "typescript": "catalog:",
+    "write-json-file": "catalog:"
+  },
+  "dependencies": {
+    "@turf/center-of-mass": "workspace:*",
+    "@turf/helpers": "^7.4.0",
+    "@types/geojson": "catalog:"
+  },
+  "engines": {
+    "node": ">=22"
+  }
+}

packages/turf-multi-geometry-scale/test.ts

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+import test from "tape";
+import {
+  point,
+  lineString,
+  polygon,
+  multiPolygon,
+  multiLineString,
+  multiPoint,
+} from "@turf/helpers";
+import { multiGeometryScale } from "./index";
+
+test("turf-group-tranlate-multi-polygon", (t) => {
+  const multiPoly = multiPolygon([
+    [
+      [
+        [102.0, 2.0],
+        [103.0, 2.0],
+        [103.0, 3.0],
+        [102.0, 3.0],
+        [102.0, 2.0],
+      ],
+    ],
+    [
+      [
+        [100.0, 0.0],
+        [101.0, 0.0],
+        [101.0, 1.0],
+        [100.0, 1.0],
+        [100.0, 0.0],
+      ],
+      [
+        [100.2, 0.2],
+        [100.8, 0.2],
+        [100.8, 0.8],
+        [100.2, 0.8],
+        [100.2, 0.2],
+      ],
+    ],
+  ]);
+
+  const multiLine = multiLineString([
+    [
+      [100.0, 0.0],
+      [101.0, 1.0],
+    ],
+    [
+      [102.0, 2.0],
+      [103.0, 3.0],
+    ],
+  ]);
+
+  const multiPt = multiPoint([
+    [100, 0],
+    [0, 100],
+  ]);
+
+  const scaleX = 1.5;
+  const scaleY = 1.5;
+  const angle = 2;
+
+  let strechedPoly = multiGeometryScale(multiPoly, scaleX, scaleY, angle);
+  let strechedLine = multiGeometryScale(multiLine, scaleX, scaleY, angle);
+  let strechedPoint = multiGeometryScale(multiPt, scaleX, scaleY, angle);
+
+  t.end();
+});

packages/turf-multi-geometry-scale/tsconfig.json

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+{
+  "extends": "../../tsconfig.shared.json",
+  "references": [
+    {
+      "path": "../turf-center-of-mass"
+    },
+    {
+      "path": "../turf-helpers"
+    }
+  ]
+}