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import type { Types } from '@cornerstonejs/core';
/**
* Orientation algoritm to determine if two lines cross.
* Credit and details: geeksforgeeks.org/check-if-two-given-line-segments-intersect/
*/
function getAllIntersectionsWithPolyline(
points: Types.Point2[],
p1: Types.Point2,
q1: Types.Point2,
closed = true
): Types.Point2[] {
let initialI;
let j;
const intersections: Types.Point2[] = [];
if (closed) {
j = points.length - 1;
initialI = 0;
} else {
j = 0;
initialI = 1;
}
for (let i = initialI; i < points.length; i++) {
const p2 = points[j];
const q2 = points[i];
if (doesIntersect(p1, q1, p2, q2)) {
intersections.push([j, i]);
}
j = i;
}
return intersections;
}
/**
* Returns all intersections points
* between a line and a polyline
*/
function getIntersectionCoordinatesWithPolyline(
points: Types.Point2[],
p1: Types.Point2,
q1: Types.Point2,
closed = true
): Types.Point2[] {
const result = [];
const polylineIndexes = getAllIntersectionsWithPolyline(
points,
p1,
q1,
closed
);
for (let i = 0; i < polylineIndexes.length; i++) {
const p2 = points[polylineIndexes[i][0]];
const q2 = points[polylineIndexes[i][1]];
const intersection = getIntersection(p1, q1, p2, q2);
result.push(intersection);
}
return result;
}
/**
* Checks whether the line (`p1`,`q1`) intersects any of the other lines in the
* `points`, and returns the first value.
*/
function getFirstIntersectionWithPolyline(
points: Types.Point2[],
p1: Types.Point2,
q1: Types.Point2,
closed = true
): Types.Point2 | undefined {
let initialI;
let j;
if (closed) {
j = points.length - 1;
initialI = 0;
} else {
j = 0;
initialI = 1;
}
for (let i = initialI; i < points.length; i++) {
const p2 = points[j];
const q2 = points[i];
if (doesIntersect(p1, q1, p2, q2)) {
return [j, i];
}
j = i;
}
}
/**
* Checks whether the line (`p1`,`q1`) intersects any of the other lines in the
* `points`, and returns the closest value.
*/
function getClosestIntersectionWithPolyline(
points: Types.Point2[],
p1: Types.Point2,
q1: Types.Point2,
closed = true
): { segment: Types.Point2; distance: number } | undefined {
let initialI;
let j;
if (closed) {
j = points.length - 1;
initialI = 0;
} else {
j = 0;
initialI = 1;
}
const intersections = [];
for (let i = initialI; i < points.length; i++) {
const p2 = points[j];
const q2 = points[i];
if (doesIntersect(p1, q1, p2, q2)) {
intersections.push([j, i]);
}
j = i;
}
if (intersections.length === 0) {
return;
}
// Find intersection closest to the start point
const distances = [];
intersections.forEach((intersection) => {
const intersectionPoints = [
points[intersection[0]],
points[intersection[1]],
];
const midpoint = [
(intersectionPoints[0][0] + intersectionPoints[1][0]) / 2,
(intersectionPoints[0][1] + intersectionPoints[1][1]) / 2,
];
distances.push(vec2.distance(<vec2>midpoint, p1));
});
const minDistance = Math.min(...distances);
const indexOfMinDistance = distances.indexOf(minDistance);
return {
segment: intersections[indexOfMinDistance],
distance: minDistance,
};
}
/**
* Checks whether the line (`p1`,`q1`) intersects the line (`p2`,`q2`) via an orientation algorithm.
*/
function doesIntersect(
p1: Types.Point2,
q1: Types.Point2,
p2: Types.Point2,
q2: Types.Point2
): boolean {
let result = false;
const orient = [
orientation(p1, q1, p2),
orientation(p1, q1, q2),
orientation(p2, q2, p1),
orientation(p2, q2, q1),
];
// General Case
if (orient[0] !== orient[1] && orient[2] !== orient[3]) {
return true;
}
// Special Cases
if (orient[0] === 0 && onSegment(p1, p2, q1)) {
// If p1, q1 and p2 are colinear and p2 lies on segment p1q1
result = true;
} else if (orient[1] === 0 && onSegment(p1, q2, q1)) {
// If p1, q1 and p2 are colinear and q2 lies on segment p1q1
result = true;
} else if (orient[2] === 0 && onSegment(p2, p1, q2)) {
// If p2, q2 and p1 are colinear and p1 lies on segment p2q2
result = true;
} else if (orient[3] === 0 && onSegment(p2, q1, q2)) {
// If p2, q2 and q1 are colinear and q1 lies on segment p2q2
result = true;
}
return result;
}
/**
* Checks the orientation of 3 points, returns a 0, 1 or 2 based on
* the orientation of the points.
*/
function orientation(
p: Types.Point2,
q: Types.Point2,
r: Types.Point2
): number {
const orientationValue =
(q[1] - p[1]) * (r[0] - q[0]) - (q[0] - p[0]) * (r[1] - q[1]);
if (orientationValue === 0) {
return 0; // Colinear
}
return orientationValue > 0 ? 1 : 2;
}
/**
* Checks if point `q` lies on the segment (`p`,`r`).
*/
function onSegment(p: Types.Point2, q: Types.Point2, r: Types.Point2): boolean {
if (
q[0] <= Math.max(p[0], r[0]) &&
q[0] >= Math.min(p[0], r[0]) &&
q[1] <= Math.max(p[1], r[1]) &&
q[1] >= Math.min(p[1], r[1])
) {
return true;
}
return false;
}
/**
* Gets the intersection between the line (`p1`,`q1`) and the line (`p2`,`q2`)
* http://jsfiddle.net/justin_c_rounds/Gd2S2/light/
* https://en.wikipedia.org/wiki/Line%E2%80%93line_intersection#Given_two_points_on_each_line
*/
function getIntersection(
p1: Types.Point2,
q1: Types.Point2,
p2: Types.Point2,
q2: Types.Point2
): Types.Point2 {
const denominator =
(q2[1] - p2[1]) * (q1[0] - p1[0]) - (q2[0] - p2[0]) * (q1[1] - p1[1]);
if (denominator == 0) {
return;
}
let a = p1[1] - p2[1];
let b = p1[0] - p2[0];
const numerator1 = (q2[0] - p2[0]) * a - (q2[1] - p2[1]) * b;
const numerator2 = (q1[0] - p1[0]) * a - (q1[1] - p1[1]) * b;
a = numerator1 / denominator;
b = numerator2 / denominator;
const resultX = p1[0] + a * (q1[0] - p1[0]);
const resultY = p1[1] + a * (q1[1] - p1[1]);
return [resultX, resultY];
}
export {
getAllIntersectionsWithPolyline,
getFirstIntersectionWithPolyline,
getClosestIntersectionWithPolyline,
getIntersectionCoordinatesWithPolyline,
};
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