249 lines
7.8 KiB
C#
249 lines
7.8 KiB
C#
// -----------------------------------------------------------------------
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// <copyright file="Contour.cs" company="">
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// Triangle.NET code by Christian Woltering, http://triangle.codeplex.com/
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// </copyright>
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// -----------------------------------------------------------------------
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namespace UnityEngine.U2D.Animation.TriangleNet
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.Geometry
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{
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using System;
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using System.Linq;
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using System.Collections.Generic;
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internal class Contour
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{
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int marker;
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bool convex;
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/// <summary>
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/// Gets or sets the list of points making up the contour.
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/// </summary>
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public List<Vertex> Points { get; set; }
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/// <summary>
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/// Initializes a new instance of the <see cref="Contour" /> class.
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/// </summary>
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/// <param name="points">The points that make up the contour.</param>
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public Contour(IEnumerable<Vertex> points)
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: this(points, 0, false)
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{
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="Contour" /> class.
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/// </summary>
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/// <param name="points">The points that make up the contour.</param>
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/// <param name="marker">Contour marker.</param>
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public Contour(IEnumerable<Vertex> points, int marker)
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: this(points, marker, false)
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{
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="Contour" /> class.
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/// </summary>
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/// <param name="points">The points that make up the contour.</param>
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/// <param name="marker">Contour marker.</param>
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/// <param name="convex">The hole is convex.</param>
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public Contour(IEnumerable<Vertex> points, int marker, bool convex)
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{
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AddPoints(points);
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this.marker = marker;
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this.convex = convex;
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}
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public List<ISegment> GetSegments()
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{
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var segments = new List<ISegment>();
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var p = this.Points;
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int count = p.Count - 1;
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for (int i = 0; i < count; i++)
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{
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// Add segments to polygon.
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segments.Add(new Segment(p[i], p[i + 1], marker));
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}
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// Close the contour.
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segments.Add(new Segment(p[count], p[0], marker));
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return segments;
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}
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/// <summary>
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/// Try to find a point inside the contour.
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/// </summary>
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/// <param name="limit">The number of iterations on each segment (default = 5).</param>
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/// <param name="eps">Threshold for co-linear points (default = 2e-5).</param>
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/// <returns>Point inside the contour</returns>
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/// <exception cref="Exception">Throws if no point could be found.</exception>
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/// <remarks>
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/// For each corner (index i) of the contour, the 3 points with indices i-1, i and i+1
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/// are considered and a search on the line through the corner vertex is started (either
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/// on the bisecting line, or, if <see cref="IPredicates.CounterClockwise"/> is less than
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/// eps, on the perpendicular line.
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/// A given number of points will be tested (limit), while the distance to the contour
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/// boundary will be reduced in each iteration (with a factor 1 / 2^i, i = 1 ... limit).
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/// </remarks>
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public Point FindInteriorPoint(int limit = 5, double eps = 2e-5)
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{
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if (convex)
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{
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int count = this.Points.Count;
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var point = new Point(0.0, 0.0);
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for (int i = 0; i < count; i++)
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{
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point.x += this.Points[i].x;
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point.y += this.Points[i].y;
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}
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// If the contour is convex, use its centroid.
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point.x /= count;
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point.y /= count;
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return point;
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}
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return FindPointInPolygon(this.Points, limit, eps);
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}
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private void AddPoints(IEnumerable<Vertex> points)
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{
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this.Points = new List<Vertex>(points);
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int count = Points.Count - 1;
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// Check if first vertex equals last vertex.
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if (Points[0] == Points[count])
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{
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Points.RemoveAt(count);
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}
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}
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#region Helper methods
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private static Point FindPointInPolygon(List<Vertex> contour, int limit, double eps)
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{
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var bounds = new Rectangle();
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bounds.Expand(contour.Cast<Point>());
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int length = contour.Count;
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var test = new Point();
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Point a, b, c; // Current corner points.
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double bx, by;
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double dx, dy;
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double h;
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var predicates = new RobustPredicates();
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a = contour[0];
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b = contour[1];
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for (int i = 0; i < length; i++)
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{
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c = contour[(i + 2) % length];
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// Corner point.
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bx = b.x;
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by = b.y;
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// NOTE: if we knew the contour points were in counterclockwise order, we
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// could skip concave corners and search only in one direction.
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h = predicates.CounterClockwise(a, b, c);
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if (Math.Abs(h) < eps)
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{
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// Points are nearly co-linear. Use perpendicular direction.
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dx = (c.y - a.y) / 2;
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dy = (a.x - c.x) / 2;
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}
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else
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{
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// Direction [midpoint(a-c) -> corner point]
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dx = (a.x + c.x) / 2 - bx;
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dy = (a.y + c.y) / 2 - by;
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}
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// Move around the contour.
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a = b;
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b = c;
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h = 1.0;
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for (int j = 0; j < limit; j++)
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{
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// Search in direction.
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test.x = bx + dx * h;
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test.y = by + dy * h;
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if (bounds.Contains(test) && IsPointInPolygon(test, contour))
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{
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return test;
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}
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// Search in opposite direction (see NOTE above).
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test.x = bx - dx * h;
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test.y = by - dy * h;
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if (bounds.Contains(test) && IsPointInPolygon(test, contour))
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{
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return test;
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}
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h = h / 2;
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}
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}
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throw new Exception();
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}
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/// <summary>
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/// Return true if the given point is inside the polygon, or false if it is not.
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/// </summary>
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/// <param name="point">The point to check.</param>
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/// <param name="poly">The polygon (list of contour points).</param>
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/// <returns></returns>
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/// <remarks>
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/// WARNING: If the point is exactly on the edge of the polygon, then the function
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/// may return true or false.
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///
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/// See http://alienryderflex.com/polygon/
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/// </remarks>
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private static bool IsPointInPolygon(Point point, List<Vertex> poly)
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{
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bool inside = false;
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double x = point.x;
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double y = point.y;
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int count = poly.Count;
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for (int i = 0, j = count - 1; i < count; i++)
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{
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if (((poly[i].y < y && poly[j].y >= y) || (poly[j].y < y && poly[i].y >= y))
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&& (poly[i].x <= x || poly[j].x <= x))
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{
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inside ^= (poly[i].x + (y - poly[i].y) / (poly[j].y - poly[i].y) * (poly[j].x - poly[i].x) < x);
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}
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j = i;
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}
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return inside;
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}
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#endregion
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}
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}
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