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First actually somewhat working js version
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Fabian Wunsch
parent
4ae1bab064
commit
53a92f29c3
1 changed files with 104 additions and 109 deletions
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@ -5,157 +5,152 @@ import TinyQueue from 'https://cdn.jsdelivr.net/npm/tinyqueue@2.0.3/index.min.js
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if (TinyQueue.default) TinyQueue = TinyQueue.default; // temporary webpack fix
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export default function polylabel(polygon, precision, debug) {
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precision = precision || 1.0;
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precision = precision || 1.0;
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// find the bounding box of the outer ring
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var minX, minY, maxX, maxY;
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for (var i = 0; i < polygon[0].length; i++) {
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var p = polygon[0][i];
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if (!i || p[0] < minX) minX = p[0];
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if (!i || p[1] < minY) minY = p[1];
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if (!i || p[0] > maxX) maxX = p[0];
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if (!i || p[1] > maxY) maxY = p[1];
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}
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// find the bounding box of the outer ring
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var minX, minY, maxX, maxY;
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for (var i = 0; i < polygon.length; i++) {
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var p = polygon[i];
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if (!i || p[0] < minX) minX = p[0];
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if (!i || p[1] < minY) minY = p[1];
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if (!i || p[0] > maxX) maxX = p[0];
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if (!i || p[1] > maxY) maxY = p[1];
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}
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var width = maxX - minX;
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var height = maxY - minY;
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var cellSize = Math.min(width, height);
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var h = cellSize / 2;
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var width = maxX - minX;
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var height = maxY - minY;
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var cellSize = Math.min(width, height);
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var h = cellSize / 2;
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if (cellSize === 0) {
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var degeneratePoleOfInaccessibility = [minX, minY];
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degeneratePoleOfInaccessibility.distance = 0;
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return degeneratePoleOfInaccessibility;
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}
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if (cellSize === 0) {
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var degeneratePoleOfInaccessibility = [minX, minY];
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degeneratePoleOfInaccessibility.distance = 0;
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return degeneratePoleOfInaccessibility;
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}
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// a priority queue of cells in order of their "potential" (max distance to polygon)
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var cellQueue = new tinyque(undefined, compareMax);
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// a priority queue of cells in order of their "potential" (max distance to polygon)
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var cellQueue = new TinyQueue(undefined, compareMax);
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// cover polygon with initial cells
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for (var x = minX; x < maxX; x += cellSize) {
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for (var y = minY; y < maxY; y += cellSize) {
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cellQueue.push(new Cell(x + h, y + h, h, polygon));
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}
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}
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// cover polygon with initial cells
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for (var x = minX; x < maxX; x += cellSize) {
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for (var y = minY; y < maxY; y += cellSize) {
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cellQueue.push(new Cell(x + h, y + h, h, polygon));
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}
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}
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// take centroid as the first best guess
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var bestCell = getCentroidCell(polygon);
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// take centroid as the first best guess
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var bestCell = getCentroidCell(polygon);
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// second guess: bounding box centroid
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var bboxCell = new Cell(minX + width / 2, minY + height / 2, 0, polygon);
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if (bboxCell.d > bestCell.d) bestCell = bboxCell;
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// second guess: bounding box centroid
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var bboxCell = new Cell(minX + width / 2, minY + height / 2, 0, polygon);
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if (bboxCell.d > bestCell.d) bestCell = bboxCell;
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var numProbes = cellQueue.length;
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var numProbes = cellQueue.length;
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while (cellQueue.length) {
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// pick the most promising cell from the queue
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var cell = cellQueue.pop();
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while (cellQueue.length) {
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// pick the most promising cell from the queue
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var cell = cellQueue.pop();
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// update the best cell if we found a better one
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if (cell.d > bestCell.d) {
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bestCell = cell;
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if (debug) console.log('found best %f after %d probes', Math.round(1e4 * cell.d) / 1e4, numProbes);
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}
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// update the best cell if we found a better one
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if (cell.d > bestCell.d) {
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bestCell = cell;
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if (debug) console.log('found best %f after %d probes', Math.round(1e4 * cell.d) / 1e4, numProbes);
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}
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// do not drill down further if there's no chance of a better solution
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if (cell.max - bestCell.d <= precision) continue;
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// do not drill down further if there's no chance of a better solution
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if (cell.max - bestCell.d <= precision) continue;
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// split the cell into four cells
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h = cell.h / 2;
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cellQueue.push(new Cell(cell.x - h, cell.y - h, h, polygon));
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cellQueue.push(new Cell(cell.x + h, cell.y - h, h, polygon));
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cellQueue.push(new Cell(cell.x - h, cell.y + h, h, polygon));
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cellQueue.push(new Cell(cell.x + h, cell.y + h, h, polygon));
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numProbes += 4;
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}
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// split the cell into four cells
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h = cell.h / 2;
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cellQueue.push(new Cell(cell.x - h, cell.y - h, h, polygon));
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cellQueue.push(new Cell(cell.x + h, cell.y - h, h, polygon));
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cellQueue.push(new Cell(cell.x - h, cell.y + h, h, polygon));
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cellQueue.push(new Cell(cell.x + h, cell.y + h, h, polygon));
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numProbes += 4;
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}
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if (debug) {
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console.log('num probes: ' + numProbes);
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console.log('best distance: ' + bestCell.d);
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}
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if (debug) {
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console.log('num probes: ' + numProbes);
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console.log('best distance: ' + bestCell.d);
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}
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var poleOfInaccessibility = [bestCell.x, bestCell.y];
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poleOfInaccessibility.distance = bestCell.d;
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return poleOfInaccessibility;
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var poleOfInaccessibility = [bestCell.x, bestCell.y];
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poleOfInaccessibility.distance = bestCell.d;
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return poleOfInaccessibility;
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}
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function compareMax(a, b) {
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return b.max - a.max;
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return b.max - a.max;
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}
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function Cell(x, y, h, polygon) {
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this.x = x; // cell center x
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this.y = y; // cell center y
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this.h = h; // half the cell size
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this.d = pointToPolygonDist(x, y, polygon); // distance from cell center to polygon
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this.max = this.d + this.h * Math.SQRT2; // max distance to polygon within a cell
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this.x = x; // cell center x
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this.y = y; // cell center y
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this.h = h; // half the cell size
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this.d = pointToPolygonDist(x, y, polygon); // distance from cell center to polygon
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this.max = this.d + this.h * Math.SQRT2; // max distance to polygon within a cell
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}
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// signed distance from point to polygon outline (negative if point is outside)
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function pointToPolygonDist(x, y, polygon) {
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var inside = false;
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var minDistSq = Infinity;
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var inside = false;
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var minDistSq = Infinity;
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for (var k = 0; k < polygon.length; k++) {
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var ring = polygon[k];
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for (var i = 0, len = polygon.length, j = len - 1; i < len; j = i++) {
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var a = polygon[i];
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var b = polygon[j];
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for (var i = 0, len = ring.length, j = len - 1; i < len; j = i++) {
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var a = ring[i];
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var b = ring[j];
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if ((a[1] > y !== b[1] > y) &&
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(x < (b[0] - a[0]) * (y - a[1]) / (b[1] - a[1]) + a[0])) inside = !inside;
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if ((a[1] > y !== b[1] > y) &&
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(x < (b[0] - a[0]) * (y - a[1]) / (b[1] - a[1]) + a[0])) inside = !inside;
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minDistSq = Math.min(minDistSq, getSegDistSq(x, y, a, b));
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}
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minDistSq = Math.min(minDistSq, getSegDistSq(x, y, a, b));
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}
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}
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return minDistSq === 0 ? 0 : (inside ? 1 : -1) * Math.sqrt(minDistSq);
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return minDistSq === 0 ? 0 : (inside ? 1 : -1) * Math.sqrt(minDistSq);
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}
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// get polygon centroid
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function getCentroidCell(polygon) {
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var area = 0;
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var x = 0;
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var y = 0;
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var points = polygon[0];
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var area = 0;
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var x = 0;
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var y = 0;
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for (var i = 0, len = points.length, j = len - 1; i < len; j = i++) {
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var a = points[i];
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var b = points[j];
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var f = a[0] * b[1] - b[0] * a[1];
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x += (a[0] + b[0]) * f;
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y += (a[1] + b[1]) * f;
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area += f * 3;
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}
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if (area === 0) return new Cell(points[0][0], points[0][1], 0, polygon);
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return new Cell(x / area, y / area, 0, polygon);
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for (var i = 0, len = polygon.length, j = len - 1; i < len; j = i++) {
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var a = polygon[i];
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var b = polygon[j];
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var f = a[0] * b[1] - b[0] * a[1];
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x += (a[0] + b[0]) * f;
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y += (a[1] + b[1]) * f;
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area += f * 3;
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}
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if (area === 0) return new Cell(polygon[0][0], polygon[0][1], 0, polygon);
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return new Cell(x / area, y / area, 0, polygon);
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}
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// get squared distance from a point to a segment
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function getSegDistSq(px, py, a, b) {
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var x = a[0];
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var y = a[1];
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var dx = b[0] - x;
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var dy = b[1] - y;
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var x = a[0];
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var y = a[1];
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var dx = b[0] - x;
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var dy = b[1] - y;
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if (dx !== 0 || dy !== 0) {
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if (dx !== 0 || dy !== 0) {
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var t = ((px - x) * dx + (py - y) * dy) / (dx * dx + dy * dy);
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var t = ((px - x) * dx + (py - y) * dy) / (dx * dx + dy * dy);
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if (t > 1) {
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x = b[0];
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y = b[1];
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if (t > 1) {
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x = b[0];
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y = b[1];
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} else if (t > 0) {
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x += dx * t;
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y += dy * t;
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}
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}
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} else if (t > 0) {
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x += dx * t;
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y += dy * t;
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}
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}
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dx = px - x;
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dy = py - y;
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dx = px - x;
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dy = py - y;
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return dx * dx + dy * dy;
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return dx * dx + dy * dy;
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}
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