@flatten-js/polygon-offset

<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width,initial-scale=1"> <title>index.js - Documentation</title> <script src="scripts/prettify/prettify.js"></script> <script src="scripts/prettify/lang-css.js"></script>  <link type="text/css" rel="stylesheet" href="https://code.ionicframework.com/ionicons/2.0.1/css/ionicons.min.css"> <link type="text/css" rel="stylesheet" href="styles/prettify-tomorrow.css"> <link type="text/css" rel="stylesheet" href="styles/jsdoc-default.css"> </head> <body> <input type="checkbox" id="nav-trigger" class="nav-trigger" /> <label for="nav-trigger" class="navicon-button x"> <div class="navicon"></div> </label> <label for="nav-trigger" class="overlay"></label> <nav> <li class="nav-link nav-home-link"><a href="index.html">Home</a></li><li class="nav-heading">Classes</li><li class="nav-heading"><span class="nav-item-type type-class">C</span><span class="nav-item-name"><a href="Offset.html">Offset</a></span></li><li class="nav-item"><span class="nav-item-type type-function">F</span><span class="nav-item-name"><a href="Offset.html#.offset">offset</a></span></li> </nav> <div id="main"> <h1 class="page-title">index.js</h1> <section> <article> <pre class="prettyprint source linenums"><code> /** * Created by Alex Bol on 12/02/2018. */ "use strict"; let Flatten = require("flatten-js"); let BooleanOp = require("flatten-boolean-op"); let {Point, Segment, Vector, Line, Box, Arc, Polygon, Face} = Flatten; let {point, segment, arc, vector} = Flatten; /** * Class Offset implements offset of polygons */ class Offset { /** * Offset polygon by given value * @param {Polygon} polygon - input polygon * @param {number} value - offset value, may be positive or negative */ static offset(polygon, value) { let w = value; let edges = [...polygon.edges]; let offsetPolygon = polygon.clone(); let offsetEdge; if (w != 0) { for (let edge of edges) { if (edge.shape instanceof Flatten.Segment) { offsetEdge = Offset.offsetSegment(edge.shape, w); } else { offsetEdge = Offset.offsetArc(edge.shape, w); } if (w > 0) { offsetPolygon = BooleanOp.unify(offsetPolygon, offsetEdge); } else { offsetPolygon = BooleanOp.subtract(offsetPolygon, offsetEdge); } } } return offsetPolygon; } static offsetSegment(seg, value) { let w = Math.abs(value); let polygon = new Polygon(); let v_seg = vector(seg.start, seg.end); let v_seg_unit = v_seg.normalize(); let v_left = v_seg_unit.rotate90CCW().multiply(w); let v_right = v_seg_unit.rotate90CW().multiply(w); let seg_left = seg.translate(v_left); let seg_right = seg.translate(v_right).reverse(); let cap1 = Offset.arcSE(seg.end, seg_left.end, seg_right.start, Flatten.CW); let cap2 = Offset.arcSE(seg.start, seg_right.end, seg_left.start, Flatten.CW); polygon.addFace([seg_left, cap1, seg_right, cap2]); return polygon; } static offsetArc(arc, value) { let edges = []; let w = Math.abs(value); // Define outline polygon let polygon = new Polygon(); let arc_cap1,arc_cap2; let arc_outer = arc.clone(); arc_outer.r = arc.r + w; arc_cap1 = Offset.arcStartSweep(arc.end, arc_outer.end, Math.PI, arc.counterClockwise); arc_cap2 = Offset.arcEndSweep(arc.start, arc_outer.start, Math.PI, arc.counterClockwise); let arc_inner = undefined; if (arc.r > w) { arc_inner = new Arc(arc.pc, arc.r - w, arc.endAngle, arc.startAngle, arc.counterClockwise === Flatten.CW ? Flatten.CCW : Flatten.CW); } else { // arc_inner = new Arc(arc.pc, w - arc.r, arc.startAngle, arc.endAngle, arc.counterClockwise); arc_inner = new Segment(arc_cap1.end, arc_cap2.start); } polygon.addFace([arc_outer, arc_cap1, arc_inner, arc_cap2]); [...polygon.faces][0].setArcLength(); // Create intersection points let ips = Face.getSelfIntersections([...polygon.faces][0], polygon.edges, false); // TODO: getSelfIntersections returns points with correspondent edges - avoid duplication ips = ips.slice(0,ips.length/2); // for now slice array to avoid duplication in points let int_points = []; let edge_cap1; let edge_cap2; edge_cap1 = [...polygon.edges][1]; edge_cap2 = [...polygon.edges][3]; for (let pt of ips) { BooleanOp.addToIntPoints(edge_cap1, pt, int_points); BooleanOp.addToIntPoints(edge_cap2, pt, int_points); } // Sort intersection points and insert them as new vertices let int_points_sorted = BooleanOp.getSortedArray(int_points); BooleanOp.splitByIntersections(polygon, int_points_sorted); // Set BV flags let bv = Flatten.OUTSIDE; for (let int_point of int_points_sorted) { int_point.edge_before.bv = bv; int_point.edge_after.bv = (bv == Flatten.OUTSIDE ? Flatten.INSIDE : Flatten.OUTSIDE); bv = int_point.edge_after.bv; // invert flag on each iteration } // Remove inner "chains" let op = Flatten.BOOLEAN_UNION; BooleanOp.removeNotRelevantChains(polygon, op, int_points_sorted, true); // return int_points_sorted; // Swap links let num = int_points.length; if (num > 0) { let edge_before; let edge_after; // 0 => 3 edge_before = int_points_sorted[0].edge_before; edge_after = int_points_sorted[num-1].edge_after; edge_before.next = edge_after; edge_after.prev = edge_before; // Fill in missed links in intersection points int_points_sorted[0].edge_after = int_points_sorted[num-1].edge_after; int_points_sorted[num-1].edge_before = int_points_sorted[0].edge_before; if (num == 4) { // 2 => 1 edge_before = int_points_sorted[2].edge_before; edge_after = int_points_sorted[1].edge_after; edge_before.next = edge_after; edge_after.prev = edge_before; // Fill in missed links in intersection points int_points_sorted[2].edge_after = int_points_sorted[1].edge_after; int_points_sorted[1].edge_before = int_points_sorted[2].edge_before; } // remove old faces BooleanOp.removeOldFaces(polygon, int_points); // restore faces BooleanOp.restoreFaces(polygon, int_points, int_points); } let face0 = [...polygon.faces][0]; if (face0.orientation() === Flatten.ORIENTATION.CCW) { polygon.reverse(); } return polygon; } static arcSE(center, start, end, counterClockwise) { let startAngle = vector(center,start).slope; let endAngle = vector(center, end).slope; if (Flatten.Utils.EQ(startAngle, endAngle)) { endAngle += 2*Math.PI; counterClockwise = true; } let r = vector(center, start).length; return new Arc(center, r, startAngle, endAngle, counterClockwise); } static arcStartSweep(center, start, sweep, counterClockwise) { let startAngle = vector(center,start).slope; let endAngle = startAngle + sweep; if (Flatten.Utils.EQ(startAngle, endAngle)) { endAngle += 2*Math.PI; counterClockwise = true; } let r = vector(center, start).length; return new Arc(center, r, startAngle, endAngle, counterClockwise); } static arcEndSweep(center, end, sweep, counterClockwise) { let {vector, Arc} = Flatten; let endAngle = vector(center,end).slope; let startAngle = endAngle - sweep; if (Flatten.Utils.EQ(startAngle, endAngle)) { endAngle += 2*Math.PI; counterClockwise = true; } let r = vector(center, end).length; return new Arc(center, r, startAngle, endAngle, counterClockwise); } } Flatten.Polygon.prototype.offset = function(value) { return Offset.offset(this, value); }; module.exports = Offset; </code></pre> </article> </section> </div> <br class="clear"> <footer> Generated by <a href="https://github.com/jsdoc3/jsdoc">JSDoc 3.5.5</a> on Mon Jun 11 2018 20:36:13 GMT+0300 (Jerusalem Daylight Time) using the Minami theme. </footer> <script>prettyPrint();</script> <script src="scripts/linenumber.js"></script> </body> </html>