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101 lines
3.2 KiB
JavaScript
101 lines
3.2 KiB
JavaScript
export function rotatePoints(points, center, degrees) {
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if (points && points.length) {
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const [cx, cy] = center;
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const angle = (Math.PI / 180) * degrees;
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const cos = Math.cos(angle);
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const sin = Math.sin(angle);
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points.forEach((p) => {
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const [x, y] = p;
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p[0] = ((x - cx) * cos) - ((y - cy) * sin) + cx;
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p[1] = ((x - cx) * sin) + ((y - cy) * cos) + cy;
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});
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}
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}
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export function rotateLines(lines, center, degrees) {
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const points = [];
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lines.forEach((line) => points.push(...line));
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rotatePoints(points, center, degrees);
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}
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export function lineLength(line) {
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const p1 = line[0];
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const p2 = line[1];
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return Math.sqrt(Math.pow(p1[0] - p2[0], 2) + Math.pow(p1[1] - p2[1], 2));
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}
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export function lineIntersection(a, b, c, d) {
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const a1 = b[1] - a[1];
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const b1 = a[0] - b[0];
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const c1 = a1 * (a[0]) + b1 * (a[1]);
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const a2 = d[1] - c[1];
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const b2 = c[0] - d[0];
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const c2 = a2 * (c[0]) + b2 * (c[1]);
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const determinant = a1 * b2 - a2 * b1;
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return determinant ? [(b2 * c1 - b1 * c2) / determinant, (a1 * c2 - a2 * c1) / determinant] : null;
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}
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export function isPointInPolygon(points, x, y) {
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const vertices = points.length;
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// There must be at least 3 vertices in polygon
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if (vertices < 3) {
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return false;
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}
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const extreme = [Number.MAX_SAFE_INTEGER, y];
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const p = [x, y];
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let count = 0;
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for (let i = 0; i < vertices; i++) {
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const current = points[i];
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const next = points[(i + 1) % vertices];
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if (doIntersect(current, next, p, extreme)) {
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if (orientation(current, p, next) === 0) {
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return onSegment(current, p, next);
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}
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count++;
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}
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}
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// true if count is off
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return count % 2 === 1;
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}
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// Check if q lies on the line segment pr
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function onSegment(p, q, r) {
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return (q[0] <= Math.max(p[0], r[0]) &&
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q[0] >= Math.min(p[0], r[0]) &&
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q[1] <= Math.max(p[1], r[1]) &&
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q[1] >= Math.min(p[1], r[1]));
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}
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// For the ordered points p, q, r, return
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// 0 if p, q, r are collinear
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// 1 if Clockwise
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// 2 if counterclickwise
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function orientation(p, q, r) {
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const val = (q[1] - p[1]) * (r[0] - q[0]) - (q[0] - p[0]) * (r[1] - q[1]);
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if (val === 0) {
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return 0;
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}
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return val > 0 ? 1 : 2;
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}
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// Check is p1q1 intersects with p2q2
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export function doIntersect(p1, q1, p2, q2) {
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const o1 = orientation(p1, q1, p2);
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const o2 = orientation(p1, q1, q2);
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const o3 = orientation(p2, q2, p1);
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const o4 = orientation(p2, q2, q1);
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if (o1 !== o2 && o3 !== o4) {
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return true;
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}
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// p1, q1 and p2 are colinear and p2 lies on segment p1q1
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if (o1 === 0 && onSegment(p1, p2, q1)) {
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return true;
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}
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// p1, q1 and p2 are colinear and q2 lies on segment p1q1
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if (o2 === 0 && onSegment(p1, q2, q1)) {
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return true;
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}
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// p2, q2 and p1 are colinear and p1 lies on segment p2q2
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if (o3 === 0 && onSegment(p2, p1, q2)) {
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return true;
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}
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// p2, q2 and q1 are colinear and q1 lies on segment p2q2
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if (o4 === 0 && onSegment(p2, q1, q2)) {
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return true;
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}
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return false;
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}
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