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import {DPolygon} from './DPolygon';
import {checkFunction} from './utils';
// eslint-disable-next-line padded-blocks
export class DCircle {
/**
* @param [center=(0,0)]
* @param [r=0]
*/
constructor(public center: DPoint = DPoint.zero(), public r: number = 0) {}
toString(): string {
return `(${this.center.toString()}, ${this.r})`;
}
getValue(): {center: DPoint, r: number} {
return {center: this.center, r: this.r};
}
clone(): DCircle {
return new DCircle(this.center, this.r);
}
/**
* Find intersection points with other circle.
*
* 
* @param c
*/
findPoints(c: DCircle): DPoint[] | number {
if (this.equal(c)) {
return Infinity;
}
const {
center: {x: x0, y: y0},
r: r0
} = this;
const {
center: {x: x1, y: y1},
r: r1
} = c;
const r02 = r0 * r0;
const d = this.center.distance(c.center);
const a = (r02 - r1 * r1 + d * d) / (2 * d);
const h = Math.sqrt(r02 - a * a);
const ad = a / d;
const dy = y1 - y0;
const dx = x1 - x0;
const hd = h / d;
const x2 = x0 + ad * (x1 - x0);
const y2 = y0 + ad * (y1 - y0);
const x31 = x2 + hd * dy;
const y31 = y2 - hd * dx;
const x32 = x2 - hd * dy;
const y32 = y2 + hd * dx;
const res = [];
if (!isNaN(x31) && !isNaN(y31)) {
res.push(new DPoint(x31, y31));
}
if (!isNaN(x32) && !isNaN(y32) && !(x31 === x32 && y31 === y32)) {
res.push(new DPoint(x32, y32));
}
return res;
}
equal({center, r}: DCircle): boolean {
return this.center.equal(center) && this.r === r;
}
/**
* Transform circle to polygon
*
* 
* @param [pointCount=64]
* @param [startAngle=0]
* @param [stopAngle=2*Math.PI]
*/
findPolygonInside(pointCount: number = 64, startAngle: number = 0, stopAngle: number = 2 * Math.PI): DPolygon {
const step = 2 * Math.PI / pointCount;
const points: DPoint[] = [];
let angle = startAngle;
while (angle < stopAngle - step) {
points.push(new DPoint(this.r).scale(Math.cos(angle), Math.sin(angle))
.move(this.center));
angle += step;
}
const x = this.r * Math.cos(stopAngle) + this.center.x;
const y = this.r * Math.sin(stopAngle) + this.center.y;
points.push(new DPoint(x, y));
return new DPolygon(points);
}
/**
* Transform circle to polygon on sphere. It would be different for different latitude.
*
* @remarks
* Center should be Lng/Lat.
*
* @remarks
* Radius should be in meters.
*
* 
* @param [pointCount=64]
* @param [startAngle=0]
* @param [stopAngle=2*Math.PI]
*/
findPolygonInsideOnSphere(
pointCount: number = 64,
startAngle: number = 0,
stopAngle: number = 2 * Math.PI
): DPolygon {
checkFunction('findPolygonInsideOnSphere')
.checkArgument('center')
.shouldBeDegree(this.center);
const step = 2 * Math.PI / pointCount;
const points: DPoint[] = [];
let angle = startAngle;
while (angle < stopAngle - step) {
points.push(this.sphereOffset(angle));
angle += step;
}
points.push(this.sphereOffset(stopAngle));
return new DPolygon(points);
}
private sphereOffset(bearing: number, earthRadius = EARTH_RADIUS_IN_METERS): DPoint {
const {x: lon1, y: lat1} = this.center.clone().degreeToRadians();
const dByR = this.r / earthRadius;
const lat = Math.asin(Math.sin(lat1) * Math.cos(dByR) +
Math.cos(lat1) * Math.sin(dByR) * Math.cos(bearing));
const lon =
lon1 +
Math.atan2(
Math.sin(bearing) * Math.sin(dByR) * Math.cos(lat1),
Math.cos(dByR) - Math.sin(lat1) * Math.sin(lat)
);
return new DPoint(lon, lat).radiansToDegrees();
}
}
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