80 lines
2.4 KiB
JavaScript
80 lines
2.4 KiB
JavaScript
import {Point} from './Point';
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import * as Util from '../core/Util';
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/*
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* @class Transformation
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* @aka L.Transformation
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*
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* Represents an affine transformation: a set of coefficients `a`, `b`, `c`, `d`
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* for transforming a point of a form `(x, y)` into `(a*x + b, c*y + d)` and doing
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* the reverse. Used by Leaflet in its projections code.
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*
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* @example
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*
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* ```js
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* var transformation = L.transformation(2, 5, -1, 10),
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* p = L.point(1, 2),
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* p2 = transformation.transform(p), // L.point(7, 8)
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* p3 = transformation.untransform(p2); // L.point(1, 2)
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* ```
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*/
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// factory new L.Transformation(a: Number, b: Number, c: Number, d: Number)
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// Creates a `Transformation` object with the given coefficients.
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export function Transformation(a, b, c, d) {
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if (Util.isArray(a)) {
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// use array properties
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this._a = a[0];
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this._b = a[1];
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this._c = a[2];
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this._d = a[3];
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return;
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}
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this._a = a;
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this._b = b;
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this._c = c;
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this._d = d;
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}
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Transformation.prototype = {
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// @method transform(point: Point, scale?: Number): Point
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// Returns a transformed point, optionally multiplied by the given scale.
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// Only accepts actual `L.Point` instances, not arrays.
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transform: function (point, scale) { // (Point, Number) -> Point
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return this._transform(point.clone(), scale);
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},
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// destructive transform (faster)
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_transform: function (point, scale) {
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scale = scale || 1;
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point.x = scale * (this._a * point.x + this._b);
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point.y = scale * (this._c * point.y + this._d);
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return point;
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},
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// @method untransform(point: Point, scale?: Number): Point
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// Returns the reverse transformation of the given point, optionally divided
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// by the given scale. Only accepts actual `L.Point` instances, not arrays.
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untransform: function (point, scale) {
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scale = scale || 1;
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return new Point(
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(point.x / scale - this._b) / this._a,
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(point.y / scale - this._d) / this._c);
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}
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};
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// factory L.transformation(a: Number, b: Number, c: Number, d: Number)
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// @factory L.transformation(a: Number, b: Number, c: Number, d: Number)
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// Instantiates a Transformation object with the given coefficients.
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// @alternative
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// @factory L.transformation(coefficients: Array): Transformation
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// Expects an coefficients array of the form
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// `[a: Number, b: Number, c: Number, d: Number]`.
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export function toTransformation(a, b, c, d) {
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return new Transformation(a, b, c, d);
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}
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